frcr part 1 revision notes
TRANSCRIPT
Revision Notes for the
FRCR Part 1
Dr Hans-Ulrich Laasch
With contributions by:
Dr Rhidian Bramley Dr Peter Bungay
Distributed By The Society Of Radiologists In Training
www.srit.co.uk
Revision Notes for the FRCR part 1
© Hans-Ulrich Laasch 1999. All rights reserved. Distributed by the Society of Radiologists in Training 05/05/2001
www.srit.co.uk
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The Society of Radiologists in Training www.srit.co.uk © Dr Hans-Ulrich Laasch 1999 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise without the prior consent of the author. This manuscript is intended as a guide to the level of knowledge required for FRCR part 1. It is neither complete nor free of mistakes. The author and publisher do not accept any legal responsibility for any errors or omissions that may be made. Please use the on-line feedback form to report any errors or omissions. www.srit.co.uk/books/feedbackform.htm
ABBREVIATIONS AND SYMBOLS a atomic number of element = number of protons (= number of electrons) λ wavelength ρ density of matter [g/cm3] z = number of neutrons + protons ~ proportional to
Revision Notes for the FRCR part 1
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PHYSICS
BASICS c = λλ·f c: speed of light (299,800 km/s) E = h·c/λλ = h·f λλ: wavelength, f: frequency Within diagnostic range λλ = 0.1 - 0.001 nm E: energy, h: constant
INTERACTION WITH MATTER 1. Elastic (coherent) scatter
complete energy transfer from photon to outer shell electron = Thomson-scatter all electron shells = Rayleigh-scatter which vibrate in resonance => excited state on return to neutral state an identical amount of energy is re-emitted from the shell as “scattered” photon => change in direction without change in energy number of interactions ~ to z² and ~ to density ρρ of the matter irradiated contribution to total scatter is negligible within the diagnostic range
2. Photoelectric effect:
interaction with tightly bound electrons, mainly k-shell, ideally when electron energy just greater then binding energy complete energy transfer from photon to photoelectron => 1. photoelectron 2. positive ion 3. subsequent characteristic radiation, absorbed within patient 4. no more x-ray photon => does not produce scatter reaching the film !!! number of interactions ~ to z³ ~ 1/keV³ ~ density ρρ characteristic radiation rarely reaches film, except from Barium and Iodine => minimal contribution to scatter, large contribution to absorbtion (for low kVp)
3. Compton scatter (inelastic scatter):
partial energy transfer from photon to loosely bound outer shell electron, no energy required to liberate recoil electron, photon continues in different direction and with increased wavelength (& lower frequency) => change in direction and in energy wavelength change dependent on angle of scatter
( )∆ Φλ = ⋅ −0 0024 1. cos maximum wavelength change = 0.48%
recoil electron accelerated in forward direction energy transfer > 60%, even if φ = 180° more forward scatter with increasing kVp number of interactions ~ 1/keV ~ density ρρ
- Within the diagnostic range Compton interactions predominate at all energies in soft tissues - The photoelectric effect predominates at low energies in bone, but diminishes quickly with increasing beam energy - within diagnostic range only small increase of Compton interactions with increasing kVp - energy of photoelectrons is higher than of recoil electrons - total scatter decreases with increasing energy, but proportionally more forward scatter reaching film => denser grid required - scatter increases approx. linear with field size to maximum at 30 x 30 cm - scatter may exceed intensity of primary beam (behind patient) i.e. abdominal film - scatter increases with absorber thickness to a saturation level
Revision Notes for the FRCR part 1
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Attenuation: = Absorption + Scatter bone : muscle = 6:1 for 20 keV monochromatic beam = 2:1 for 100 keV èè lower contrast at higher energy (high kV chest x-ray!)
Intensity beam intensity is proportional to ~ tube current ~ kVp² ~ z (atomic number of target material)
Transmitted intensity (number of transmitted photons) N N e d= ⋅ − ⋅0
µ
N0 = incident intensity, µ = linear attenuation coefficient, d = thickness of absorber
Linear attenuation coefficient (LAC), µ: attenuation per distance travelled in medium, sum of all interaction effects [ /mm] µtotal = Σ [µelastic + µCompton + µphotoelectric] varies not only for medium but also for its physical state and density µiodine > µbone > µmuscle > µfat, insignificant for high kV
Mass attenuation coefficient (MAC): LAC corrected for density, MAC = LAC/ρ attenuation per unit mass of attenuator [cm²/g] fat > muscle > bone > iodine ~ to number of electrons/gram tissue
Inverse square law
intensity of beam decreases with the square of the distance from a point source => best radiation protection is distance does not directly apply to large sources, i.e. patient during radioisotope scan
PRODUCTION OF X-RAYS Cathode ray tube working in the temperature limited/saturated part of its characteristic curve
1. stationary anodes angled W target mounted in Cu-block 2. rotating anode mushroom shaped Mo anode rotating at high speed to increase heat dissipation
Anode rotates at 3000 rpm standard, 9000 rpm high speed => increased thermal capacity made of Molybdenum or Carbon (light) Mo stem - poor heat conduction to insulate bearings bearing lubricants must be solid (Pb, Ag) as within vacuum of tube
Target area of tungsten-rhenium (10%) alloy => improved thermal capacity and resistance to roughening
Tungsten: 18474W highest melting point of all metals (3380° C)
low vapour pressure good thermal capacity k-edges at 59 and 69 keV => minimum of 75 kVp required
tube current = approx. 1/10 filament current
for fixed filament current the tube current reaches a maximum with increase of the tube voltage as the space charge cloud is sucked off to the anode (= saturation)
x-ray tube works on the plateau = saturated region and the tube current is regulated by increase in cathode current/temperature
kVp peak potential between cathode and anode in kilovolt
should be maintained to within ± 5kV max. mA tube current in milli-Ampere mAs tube current multiplied with exposure time
= total charge (number of electrons) that were accelerated from the cathode onto the anode 1 mAs = 1 Coulomb = 6.24 x 10
18 electrons
charge of one electron = 1.602 x 10-19
C
Revision Notes for the FRCR part 1
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Bremsstrahlung (German: deceleration radiation)
when electrons hit the anode most (> 99%) give up their energy as heat through interaction with the electron shell of the target atoms a minority of electrons (< 1%) interact with nuclei of target material and give off their energy as high energy electromagnetic radiation, called “x-rays” by W. C. Roentgen 1896 efficiency of x-ray production increases with atomic number, z of target
Heat transfer Radiation: transfer through infra-red electromagnetic waves, traverses vacuum, i.e. anode to envelope (also used in standard kitchen grill and toaster) Convection: transfer from solids to gas or liquids causing motion of the molecules i.e. envelope to oil (= fan assisted oven) Conduction: transfer through opaque solids i.e. anode to stem to bearings (attempt to keep this low by using Mo stems) (= hot lid handle) Stefan’s law of radiation: heat transfer is proportional to temperature
4 in Kelvin
Fourier's law of heat conduction: heat conduction through an opaque body is proportional to the negative of the temperature gradient in the body. The proportionality factor is called the thermal conductivity of the material. (Jean Baptiste Joseph FOURIER 1882)
Tube rating increased by - small anode angle (for same effective focal spot size) à larger target area - fast anode rotation - three phase tubes at short exposures, but single phase rectified voltage at long exposures
k-edge binding energy of electrons on the k-shell of an atom (= shell closest to nucleus),
to expel electrons from that shell by photoelectric or Compton-effect the energy required is slightly above the binding energy high absorption of x-rays at that energy and below => important for filters after a k-electron had been expelled the deficit in the k-shell is filled by electrons ‘dropping down’ from outer electron shells (i.e. l,m,n). During this they emit characteristic radiation of discrete energy peaks. for kVp > 75 kV the characteristic radiation of a tungsten target contributes 10-15% to the intensity of the primary beam
Pb 88 keV 20782 P b
W 58.5 and 69.5 keV 18474W
Ba 37.4 keV I 33.2 keV Sn 29 keV Mo 17.5 and 19.6 mammography target and filter Se 13 keV xeroradiography Cu 8 keV Ca 4 keV Al 1.6 keV rare earths 17 - 50 keV
Components of filament circuit: mains autotransformer, electronic stabiliser,
space charge compensator, voltage stepdown Autotransformer one coil only, low resistance, combines self and mutual induction Pre-reading voltmeter: indicates acceleration voltage across tube Exposure timers - synchronous. timers, integrating screening timers synchronous motors
- electronic timers capacitors, thyristors, mAs-timers - phototimers light from fluoroscopy screen
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X-ray generators
Quality of X-rays dependent on kVp and waveform Quantity dependent on anode current, waveform and proportional to kV² and z of anode efficiency of x-ray tubes around 1% Wave-forms maintaining of tube voltage (kV) over time
in older generators negative half-wave of mains AC was either cut off or converted to a positive half-wave = rectified 1. single phase half-wave rectification 2. full wave rectification (single phase without smoothing) => pulsed voltage 1/10 ms (100Hz) 3. three phase full-wave rectification => near-constant potential
3-phase generators maintain tube voltage pulses within 3.5% of kVp = approx. constant potential modern generators are all constant potential generators and work independent of the mains 50 Hz alternating current
Falling load generator
aimed at high output work with long exposures tube current maintained at maximum until critical heating of anode requires step-wise reduction via rheostat useful for ortho-clinic (l-spine etc.), not useful in chest work due to short exposures and small loads usually in same room as tube
Mobile units a. single wave generators
rectified half-wave, uses 30 Amp. ring main => requires special points throughout hospital b. constant potential generators
continuous rather than pulsed tube current => kVp = kVeff => shorter exposure times 1. battery (NiCd) powered containing charge of 10 Coulomb (10.000 mAs) DC inverter produces AC at 500 Hz with fixed current of 100 mA => easy calculation of exposure time 2. capacitor powered charged from standard 13 A main inverter produces AC at 4.5 kHz (!)
c. capacitor discharge units 1 µF (1 Farad = 1 Coulomb/Volt) capacitor discharges directly into a special grid-controlled x-ray tube (= triode) grid at 2 kV negative potential to cathode, when switched off discharges burst of electrons rather than pulsed wave form very precise control of tube current and short exposure times compared to “mechanical” relays
Anode Heel Effect: intensity of beam is lower on anode side of field, as radiation has to traverse the longer edge of the
bevelled anode target area. Focal spot size: a. actual focal spot size 0.6 - 1.3 mm for general purpose
0.1 - 0.3 mm in mammography and high detail units measured by pinhole camera, slit tool (two slits at 90°), star test tool measurements are accurate to ± 25-50 % only, but minimal effect of variation in FSS on image quality only b. effective focal spot size measured centrally in primary beam dependent on filament size, anode angle, tube current and voltage decreases with increase in kVp increases in direct proportion to anode current = focal spot blooming extremely small focal spot sizes (< 0.1 mm) can be achieved with electrostatic focusing
Anode angle 9-17° for general purpose, the smaller the angle, the more pronounced the anode-heel effect Line pair resolution test tool = high contrast resolution test tool
(i.e.. star test pattern) measures resolving capacity, which is function of spot size as well as radiation intensity distribution.
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Focal spot size estimated too large if edge band distribution of intensity, too small if centrally peaked Penetrameter cassettes, i.e. Wisconsin cassette, Adrian Crooks cassette, Sussex cassette Electronic penetrameter
measure kVp by comparing the penetration through a copper step wedge against standardised lead attenuators variation ± 5 kVp acceptable standard double sided emulsion + intensifying screen, screen covered by optical attenuators film blackening under copper disks decreases, constant under lead mask, cross over of film blackening is a measure of the energy of the beam
Reciprocity law as the intensity of the beam is product of tube current and exposure time,
high exposure for short time and low exposure for long time should result in the same film blackening (for constant kVp) in practice long exposure times result in lower film blackening than expected, supposedly a problem of the x-ray/light conversion in the intensifying screens noticeable in mammography
Filtration = removal of unwanted low energy radiation that would contribute to surface dose, but not to formation of the image good filtration can reduce the skin dose by 50-75% for plain films Half value layer d½ reduces beam to half the incident intensity
HVL =
0 693.
µ for thickness = n times the HVL, the beam intensity reduces to 1/2
n
i.e. n=10, intensity = 1/1024 for polychromatic (-energetic) beam the HVL increases with attenuation, as the beam is hardened after 4x d½ beam practically monochromatic for 60 kVp HVL for soft tissue ~ 3 cm Aluminium ~ 1 mm
Inherent tube filtration approx. 0.5-1 mm Al-equivalent, absolute minimum for W-targets = 0.5 mm Al-equivalent
contributors: target itself > casing > cooling oil > exit window
Minimal added filtration (to 0.5 mm Al-equivalent of inherent filtration) < 70 kVp 1.5 mm Al 70 - 100 kVp 2.0 mm Al > 100 kVp 2.5 mm Al undercouch fluoroscopy 2.5 - 4 mm Al as short FOD CT up to 7 mm Al equiv. as 3mm brass filter / bow tie filters Aluminium useful as 1. K-edge 1.6 keV
2. characteristic radiation absorbed in air 3. readily available and easy to apply
Copper requires a backing filter of Al to absorb characteristic radiation of 8 keV Molybdenum and Palladium filters used in mammography, usually with Mo and W target respectively The Grid Physical “sieve” to reduce the amount of scatter (that is produced in the patient) reaching the film. It consists of thin lead
strips which are interspersed with layers of Aluminium or carbon fibre. Radiation that is not parallel to the lamellae is filtered out depending on the angle.
grid ratio height of strips : distance between them, usually 4:1 - 16:1
grid density number of lamellae per cm, commonly spaced at 30-50/cm
individual lead strips appr. 0.05 mm thick => gap between strips much larger than strip thickness
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contrast improvement factor = contrast with grid : contrast without grid, this is also dependent on - kVp } - field size } amount of scatter - object thickness }
bucky factor correction of exposure factors required, when grid is introduced Types of grids parallel grid simplest form, parallel strips arranged perpendicular to film plane, no geometrical limitations focused grid the outer lamellae are increasingly angled in order to follow the line of the diverging x-ray beam.
Can only be used at a specific FFD (or focus-grid distance), otherwise grid cut-off occurs. Needs to centred other wise lateral decentering occurs.
crossed grid two sets of lamellae at right angles, rarely used, high bucky factor Grid artefacts grid cut-off if a focused grid is used at the wrong FFD the angled lateral lamellae will filter out part of the primary
beam => the lateral edges of the film become symmetrically underexposed. Also occurs if the grid is upside down or tilted.
lateral decentering if the grid is not centred to the primary beam asymmetrical underexposure of the film will occur.
PHOTOGRAPHY electron-shell model for atoms modified to band-model in solids 3 main types of bands conduction band: high energy level, electrons can move freely to conduct electricity
forbidden band: does not contain free electrons but electron traps near conduction band and hole traps near valence band valence band: low energy level, contains valence electrons
Fluorescence electron-traps filled
x-ray effects elevate many electrons from valence to conduction band the created holes in valence band move to hole traps in forbidden band electrons from e-trap fall spontaneously (no extra energy required) into hole trap emitting visible light excited electrons from conduction band fill electron traps fast process, light emission within 10 µs
Phosphorescence electron traps empty
transition of excited electrons from conduction band to valence band fall into e-traps transition back into valence band only possible by being elevated into conduction band again => small amount of energy required, usually enough fluctuations within molecule, but can be facilitated by heating => delayed process, > 10 µs => light emitted of higher energy than with fluorescence
Thermoluminescence transition into high energy state from e-trap requires so much energy that this does not occur
spontaneously activated state very stable, light emitted on heating
Intensifying screens (of film-screen combinations)
layers: 1. base ± reflecting layer 2. phosphor, 100 µm thick (film emulsion 10-20 µm) 3. protecting layer => can be cleaned with soap and water
multiply one x-ray photon into several thousand* light photons - increase contrast - reduce patient dose - reduce exposure times - increase photographic unsharpness
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1. Calcium-tungstate (*1:1000) blue light up to 430 nm 2. 2. Rare earth screens (*1:4000)
1. gadoliniumoxysulphide green light up to 570 nm Kodak-system (green for Godak) 2. lanthanum blue light up to 430 nm Dupont-system impurities within screen improve fluorescent properties = “Terbium activated”
NB: green sensitive film is also sensitive to shorter wavelengths of blue screens, but not vice versa screens increase speed and reduce latitude two screens as opposed two one double the radiographic contrast Absorption fraction of incident x-ray photons interacting with screen
Ca-tungstate 30% rare earths 60% due to lower k-edges
Conversion efficiency ratio emitted light photons / absorbed x-ray photons Ca-tungstate 5% rare earths 20% due to lower k-edges
Screen efficiency proportion of emitted light photons that reach the film, ~50% Intensification Factor ratio required exposure without screen / exposure with screen
increased with higher kV, thicker screen, larger phosphor crystals Radiographic film Emulsion 90% AgBr, 10% AgI
sensitised with sulphur molecules = sensitivity specks, reduce interstitial Ag-atoms to latent image Double-sided, commonest => seven layers
1. base polyester, 180 µm thick, contains blue dye for easier viewing, pigment to reduce cross-over from screens to opposite emulsion, washed out during processing 2. substratum (x2) adhesive, bonds base to emulsion (“subbing layer”) 3. emulsion (x2) silverhalides, mostly AgBr, ~ 20 µm thick contains dye to prevent light diffusion and cross-over, washed out in fixer 4. supercoat (x2) gelatine, protects
Single sided (with or without a single screen) 1. coating with anti-halation backing
2. base 3. substratum 4. emulsion 5. supercoat
emulsion and screen on the side of the base facing away from tube (x-rays penetrate film before reaching screen) the side of the film facing the tube (i.e. not containing the emulsion) is coated with an anti-halation backing to prevent light from screen that has penetrated film being reflected back onto emulsion used in - mammography
- copy film - high detail systems - dental radiography
Density D optical density, measure for film blackening,
D
I
I trans
= log 100
expressed as logarithm of ratio of incident and transmitted intensities as 1. logarithmic response of human eye to light 2. easy expression of a wide range of ratios 3. sum of densities of several films is the sum of their individual densities Dtotal = D1 + D2 + Dn useful density range for viewing: 0.2 - 2.5 film blackening is a function of kV
4 for screen-film combinations
Characteristic Curve of a film is the density as a function of the decimal logarithm of the exposure
four parts of the curve besides the emulsion it is also dependent on the screens and the processor conditions 1. toe initial curved part with finite minimum density for unexposed areas = base fog 2. linear part steepness γγ represents latitude of film 3. saturation plateau of maximal film blackening 4. solarization further increase in exposure decreases film blackening due to recombination of
Revision Notes for the FRCR part 1
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silverhalides copy films are solarized, exposure through the “light” parts of the original film lead to reduction in the density
in that area in the copy film, => the longer the exposure in the copying process, the lighter is the produced film Contrast Contrast = difference between two densities
C D D
I
I= − =2 1
2
1
10log
human eye can differentiate differences in optical densities of up to 0.04% = 10% difference in intensity of transmitted light
Subject contrast dependent on relative difference in absorption coefficients between structures, i.e.
- subject thickness - subject density - atomic number z - kV
Film contrast / film gamma, γ if = 1 reproduces subject contrast, if >1 amplifies subject contrast
Radiographic / film contrast) dependent on subject contrast, scatter
Subjective contrast dependent on radiographic contrast, viewing conditions
Unsharpness (blurring)
Failure to reproduce a distinct edge as a line total unsharpness equals the square root of the sum of the individually squared components hence the total unsharpness approximates the largest single contributor
U U U U Ut g p m a= + + +2 2 2 2
1. geometric unsharpness
a. penumbra focal spot not infinitely small => lines become bands b. magnification reduced with small OFD and large FOD 2. photographic unsharpness a. screen unsharpness light diffusion within screen phosphor layer, worse with faster screens as phosphor thicker b. parallax-effect of double emulsion films emulsions separated by film base (~ 180µm) as beam diverges images on either side not completely congruent, effect minimal c. light cross-over light from screen 1 exposes grains in emulsion 2 and vice versa 3. motion unsharpness patient movement, respiration, heart-beat etc., reduced by short exposures and immobilisation 4. absorption unsharpness if object imaged has a curved edge the tangential beam fails to define a distinct margin
Magnification ratio of focus-film to focus-object distance
Mag
FFDFOD
.=
NB: magnification = 2 => object 100% magnified, i.e. twice original size magnification = 1 => object reproduced in original size magnification radiography requires very fine focal spots to reduce geometric unsharpness
Speed reciprocal of the exposure required to produce a density of 1 above base + fog (usually about 1.2)
increasing the speed of a film-screen combination - reduces patient dose - reduces exposure time - reduces sharpness - reduces contrast - has no direct effect on quantum noise (unless dose reduced) - increases fog
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Gamma (γγ) steepness of curve, represents latitude of film dependent on grain-size in film emulsion and range of grain-size, as well as processing factors for subtraction film = +1 => gives a negative of the image for copy film = -1 => gives a positive of the image
Latitude film latitude: range of different densities the film can produce
wide latitude = lots of shades of gray, low contrast narrow latitude = high contrast film, i.e. lithographic film latitude is a function of the range of the grain size of the emulsion exposure latitude: range of exposures covered by the linear part of the characteristic curve wide exposure latitude => wide range of exposure settings tolerated
Density Contrast Latitude Speed Unsharpness
Grain size large ⇑ small ⇓ Range wide ⇑ ⇑ ⇑ narrow ⇓ ⇓ ⇓ Processor- increased ⇑ ⇑ ⇑ activity decreased ⇓ ⇓ ⇓ Fog & scatter ⇑ ⇓ ⇑ Resolution Ability to reproduce fine detail, measured in linepairs/mm human eye can resolve 10-15 lp / mm Line spread function
ability to reproduce a thin (10 µm) slit in a platinum plate as a thin line of the same width images obtained usually order of magnitude wider than object intensity distribution of obtained image ideally hat-shaped, in practice more or less bell-shaped measure for accuracy of reproduction = width of intensity peak at 50% of peak intensity => full width half maximum, FWHM
Modulation -transfer function, MTF
efficiency at reproducing spatial frequencies (SF) resolving power measured in linepairs/mm for MTF 10% MTF values are acquired by 2 dimensional Fourier transformation of the line spread function of a very thin wire or slit in a platinum plate MTF of 1 = 100% reproduction of spatial frequencies for a radiographic chain with n components: MTFout = SFin · MTF1 · MTF2 · MTFn MTF of non-screen film > screen-film-combination > image intensifier > TV-camera (20 lp/mm) (5-8 lp/mm) (2-4 lp/mm) fluoroscopy chain: focal spot > image intensifier > movement unsharpness > camera xeroradiography: poor for low spatial frequencies (< 5 lp/mm) optimal between 10-50 lp/mm, then tails off again tomography 2 lp/mm mammography 20-22 lp/mm CT 0.5-1 lp/mm 80% for 0.2 lp/mm 50% for 0.4 lp/mm 10% for 0.6 lp/mm MTF is not affected by quantum noise improves with magnification and reduced FOD, as spatial frequencies reduced
Limits of resolution low contrast quantum noise
high contrast unsharpness Noise Radiographic mottle inhomogeneity in density not caused by contrast of image 1. Film graininess worse for high speed film
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2. Screen mottle inhomogeneities of intensifier screen 3. Quantum mottle (- noise), QM
fluctuation of radiographic density around average due to statistical variation of recorded counts per unit area of detectors (film or scintillation crystals, ionisation chambers etc.) distribution of incident photons across detector array/film crystals is a random process => Gaussian distribution of recorded counts per detector around average for average detected counts = N, the absolute fluctuation around the mean = N
½
proportional fluctuation for N counts per detector/pixel = N½/N => much more important at small numbers of
recorded counts i.e. for N=10
1 counts, variation = ±3 or 30%
N=104 counts, variation = ±100 or 1%
N=106 counts, variation = ±10
3 or 0.1%
quantum noise does not affect the MTF (but important for low contrast resolution) does not increase with magnification of image, as photon flux unchanged
Noise in CT, DSA and γγ-detectors is dominated by quantum mottle Film Processing Fog 1. Inherent fog ideal storage factors: temperature < 21°C, low humidity (but too dry: increased static!)
sealed from light and x-rays 2. Light light spread (= bad sandwich)
poor screen / film contact; foreign bodies 3. X-rays scatter 4. Chemical poor quality processing: contamination of chemicals, increased processing activity, temperature or time
dichromate fog: silver not washed out fully during fixing => delayed sepia-discoloration
Base + fog density of unexposed film, dependent on 1. + 4. + density of polyester base, should be less than 0.2 Speed exposure required to produce a density of 1 over base + fog Dark-room 9m
2 rectangular floor area, 3m high ceiling
air turned over 8-10 times/h central location
Developer temperature within ± 0.2° C Fixer silver content between 4-6 g/l Quality assurance, QA and quality control, QC Frequencies of testing:
Sensitometry daily reserved box of films step-exposure with sensitometer readings with densitometer - unexposed area = base + fog - density step of 1 over base = speed - density step of 1 over speed = contrast AEC at least annually copper step wedge/penetrameter at different settings => output within 10 % of target settings focal spot size if deterioration suspected line pair/star test tool, pinhole if FSS > 0.6 mm filtration after tube service film-screen contact as required grid image gets distorted in areas of poor contact Tomography 6/12 slice thickness, height and arc uniformity of exposure over arc reject analysis of throw outs periodically aiming at < 10% repeat rates
Digital subtraction radiography wide range of film γγ-equivalents can be simulated logarithmic conversion of raw data post-acquisition narrowing of window does not increase noise (original photon flux unchanged) but makes it more noticeable
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IMAGE INTENSIFIER CsI input phosphor converts g-photons into light photons which are emitted onto a photocathode long
crystals in direction of photons, reflect light laterally, reduce scatter highly hygroscopic, air-tight enclosure required => needs to be transparent at post. surface
Photocathode converts light from input phosphor into electrons which are accelerated through 30-40 kV on a curved path towards the (smaller) output phosphor
Zn-Cd-sulphide output phosphor converts electron beam back into (green) light, inverted image, Al-backing on cathode-side to prevent back scatter of light to photocathode
intensification through 1. minification
2. acceleration of electrons = flux gain x 50
Minification gain (d = diameter of phosphor) x 100-200
α
d
di n p u t
o u t p u t
2
Conversion efficiency measure of quality of input phosphor
=
−
lightx rays
cd mGy s
out
in
;/
/
2
µ
dose rate image intensifier requires 0.5µG/s best detectable contrast difference = 5%
Automatic gain control varies gain = amplification within monitor without change in exposure factors
Automatic brightness control varies kVp and mAs
Distortion S-shaped: gravity effect pincushion: electronic problem
Veiling glare mainly scattering of light in output phosphor, corresponds to screen scatter in cassettes occurs in image intensifier or TV camera worse in thick tissues
Vignetting reduction of brightness towards edge of screen due to longer, curved path of electrons from periphery of input phosphor => inverse square law applies curved input phosphor, straight output phosphor => autocorrection possible
Resolution similarly poorer at screen edge due to difficulties with electronic focusing Magnification improves resolution
increases noise, if dose remains unchanged TV-camera Output phosphor of intensifier tube emits light photons towards the light-sensitive target plate of the camera. The target plate liberates electrons where hit by light (photo-electric effect). Electrons produced by this process are accelerated through 250 V onto signal plate and charge areas corresponding to the original light exposure from the intensifier tube. Signal plate has a positive potential against cathode at other end of tube and is scanned by electron beam from the cathode Target plate photosensitive material, emits electrons where hit by light, these charge corresponding areas of the
signal plate antimony trisulphate in mica matrix in Vidicon system lead monoxide in Plumbicon system
Signal plate graphite plate electrode with + 25V potential against cathode gets charged by excited areas of target plate
Electron beam current from camera cathode to signal plate focused and moved by 2 sets of coils to scan signal plate in 625 horizontal lines localised charge on signal plate is released by beam and the current across tube registers small pulses corresponding to areas that were exposed to light a specific signal demarcates the beginning of each new line the pulses in the tube current allow temporal and spatial resolution
Bandpass maximal pulse frequency the processor can handle without distortion
Vidicon target has more lag as picture decays slower
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=> image blurring on movement of image intensifier => reduced quantum mottle as statistical variations are averaged out
Plumbicon camera faster than Vidicon, but more noise
COMPUTED TOMOGRAPHY, CT Anode voltage 120 - 150 kVp, constant potential ± 0.01 % (!) heavily filtered (≤ 0.5 mm Cu, equivalent to 7-8 mm Al) => approx. momoenergetic beam of 70 keV focal spot 0.6 mm pre- and post-patient collimation, slice thickness within ± 0.5mm high dose examination, CT contributes to 2.5% of medical examinations, but to 25% of medical irradiation
effective dose, E head 1.8 mSv abdomen 7.2 mSv chest 8.3 mSv
CT-scanners 1. generation pencil beam, single detector, both rotate scan every 1° of 180° semi-circle at different lateral translations => translate-rotate scanning 2. generation fan beam with multiple detectors covering appr. 15°, beam width narrower than slice width => translate-rotate scanning 3. generation fan beam with detector array wide enough to scan full slice width, therefore translation obsolete tube and detectors rotate, fast acquisition < 5sec/slice => rotate-rotate scanning, helical scanning 4. generation rotating tube, fixed 360° ring of solid-state detectors => rotate-fixed scanning, helical scanning, possible due to slip-ring technology electric supply Imitron cup-shaped vacuum tube which surrounds patient 270° containing Wo-target areas as well as multiple detectors electron beam electronically focused onto target areas in walls of cup which generate x-ray beam through patient towards detectors on the other side extremely fast, no moving parts, freezes cardiac cycle one scanner in the UK in 1996 Helical CT (helix = spiral with constant radius) continuous image acquisition during continuous table feeding = volume acquisition of the whole block of tissue, slices can be reconstructed to the desired thickness after acquisition, down to a minimal slice thickness = beam collimation allows faster scan time (i.e. vascular), reduced patient dose and three-dimensional reconstruction Three important parameters: a. collimation: width (thickness) of x-ray beam during acquisition (e.g. 8-10mm in abdomen) b. Pitch: ratio of table movement:collimation i.e. table moves 12 mm during one revolution with 8mm collimation = pitch of 1.5 increased pitch allows faster scanning and reduces dose, but leads to some loss in resolution, however this is minimal up to a pitch of 1.5 c. index: thickness of the reconstructed slice, these are often reconstructed overlapping each other, e.g. 8mm slices at 7mm intervals overlap 0.5 mm either side Multi-slice (multi-detector CT) Several (i.e. 4) interlaced spirals are acquired at the same time, allowing faster table feed, shorter scan times and high-definition three dimensional reconstructions (i.e. aorta, biliary tree)
Detectors 1. scintillation crystals (NaI/CsI)
hygroscopic and sensitive to mechanical and thermal insult suffer from afterglow 2. gas ionisation chambers
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very stable but insensitive 3° scanners 3. modern solid state CdW-crystals coupled with silicon photodiodes (semiconductors) fast, reliable but expensive 104x more sensitive than gas detectors, > 99% absorption of x-rays 3° and 4° scanners
Hounsfield scale Relative measure of attenuation in computed tomography. Water = 0, cortical Bone = +1000, Air = - 1000 Most parenchymal organs between 0 and + 100 Fresh clotted blood + 90 (= white on narrow brain windows)
+ 1000 -¦------------------------------ Cortical Bone ---------------- ¦ bone marrow -¦ ¦ + 100 -¦- - - - - - - - - - - - - - - - - - - - - - - - - - - - ¦ fresh haemorrhage ¦ Liver ¦ Brain (grey matter) Spleen > Kidney, Pancreas, Bowel ¦ Brain (white matter) Adrenal ± 0 -¦---------------------------------- Water ------------------- ¦ | ¦ | | ¦ |Fat |Breast ¦ | | - 100 -¦- -|- - - - - - - - - - - - - - - - - - - - - - - - - - ¦ -¦ | ¦ |Lung - 1000 -¦------------|---------------------- Air ---------------------
windowing window is selected to cover the attenuation of the “region of interest”
attenuation values above the upper limit will appear in white, below the lower limit in black window width = range of units that will be represented as a shade of grey window centre = Hounsfield value defining the middle of the represented range i.e. WW: 500, WC: -400 structures of a higher attenuation than -150 will be depicted in white, everything below -650 in black. Structures between -150 and -650 will appear in shades of grey. example would be useful to investigate areas of fat or lung tissue, but will not be able to differentiate between bowel, liver or bone.
CT monitor can represent 256 greyscales human eye can differentiate 10-15 greyscales narrowing WW reduces quantum noise
Linearity ability to represent a linear increase in attenuation as a linear increase in Hounsfield units Spatial uniformity ability to represent every voxel of a uniform object by the same Hounsfield-unit throughout the image,
checked with water phantom monthly Spatial resolution ability to distinguish two small high-contrast objects located close together under noise-free conditions Slice sensitivity profile
ideally hat-shaped = no sensitivity outside the slice, but maximum sensitivity from edge to edge in practice sensitivity tails beyond slice edges and slope from edge to sensitivity plateau described in terms of full width (of sensitivity curve) at half maximum (sensitivity), FWHM profile improved by post-patient collimation, but significant increase in patient dose
Magnification enlarges a part of the image including the pixels and the noise => resolution unchanged
Zoom recalculates a part of the raw data of the image over the whole matrix => resolution improved CT-Artefacts 1. streak artefacts misalignment and motion
2. ring artefacts detector non-uniformity (damage), particularly severe in SPECT 3. beam hardening as beam gets filtered by superficial tissues 4. aliasing high frequency noise at sharp, high contrast interfaces => low frequency detail
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Extremities usually 8 mm slices at 16 mm intervals (i.e. non-contiguous with 8 mm gaps)
for joints 2-4 mm contiguous slices
ULTRASOUND, USS
Frequencies above 20 kHz, no natural background, medical: 1-20 MegaHz c
air 340 m/s
cfat
1450 m/s
cwater
1540 m/s
csoft tissue
1400 - 1600 m/s
cskull
4080 m/s
Piezoelectric effect Appearance of an electric potential at the surfaces of a crystal when it is subjected to mechanical pressure. Conversely, when an electric field is applied to the crystal, it undergoes mechanical distortion. Jacques and Pierre Curie discovered the phenomenon in quartz and Rochelle salt in 1880 and named the effect piezoelectricity (Greek piezein, “to press”). 1. Quartz 2. lead zirconate titanate 3. complex composites => modern transducers applied voltage 150-300 V resonance frequency of crystal dependent on thickness, not diameter
d = λ/2, 4 MHz for 0.5mm
Ultrasound BeamTransducer
1 - Damping layer
2 - Crystal of radius r
3 - Matching layer of thickness d
Near (Fresnel) zone Far (Fraunhofer) zone
r
d
electrodes
1 2 3
Damping layer minimises oscillating time, shortens US-pulses z of matching layer is equal to geometric mean impedance of crystal and tissues to be scanned Maximum transition if thickness of matching layer d = ¼ λλ Thickness of crystal = λλ/2 Length of near zone l = r²/λλ
Diverging angle of far zone sin .α
λ= 122
2r Increasing the scan frequency increases the near zone
increases the diverging angle increases absorption
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Types of transducers Mechanical small footprint Sector array diverging beam, standard scan head Linear array crystals arranged along short axis of probe
number of crystals determines number of lines in image increase in lines reduces Fresnel zone => compensated for by triggering crystals in groups of four or five groups of crystals fired in one by one in quick succession, all receive echo of their own signal vertical lines of image represent acoustic corridor of each individual group parallel beam unless “curvi-linear array” slice thickness determined by crystal length and correction via acoustic lens
Phased array delay in triggering individual crystal allows electronic focusing and beam steering all crystals fire during acquisition of each line, beam direction and focus varies with each pulse => sector array gated for reception = single crystals receive “their” line small footprint
Acoustic impedance, z
z = p/v p - instantaneous excess pressure v - instantaneous particle velocity z = ρρ·c ρ - density of material c - speed of sound in material
Ultrasound and tissue 1. Reflection change of impedance z1 => z2
interface large » wavelength roughness « wavelength reflection coefficient for normal incidence (90°):
R
z z
z z=
−+
1 2
1 2
2
90% at soft tissue / air interface 50% at soft tissue / bone interface < 1% at soft tissue / soft tissue interface
2. Scatter scattering object « wavelength roughness » wavelength
3. Refraction change of speed of sound, direction and wavelength at interface, not of frequency Snell’s law:
s i n ( )
s i n ( )
ir
c
c= 1
2 i = angle of incidence, r = angle of refraction, c = speed in medium 1+2
c c f f1 2 1 2 1 2≠ ≠ =, ,λ λ 4. Absorption mechanical energy converted to heat through relaxation processes
energy falls exponentially with depth for soft tissues the absorption is proportional to the USS frequency
Attenuation overall loss of intensity through a single medium
decibels dbII
( ) log=
10 101
2 tissue attenuation approx. 1 dB / cm x MHz The intensity of the reflected echoes is reduced by factor 10.000 as compared with the original signal = 40 dB
Line spread function measured with nylon wires in a phantom
Lateral resolution improved with high frequency, small crystal and good focusing ∝
fr
approx. 3 mm at 3 MHz Axial resolution ~ 10x better than lateral, approx. ½ length of pulse
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Length of sonic pulse = wavelength x number of waves
λλ approx. 0.5 mm for 3MHz, 0.3 for 5 MHz (assuming c=1500 m/s)
Q-factor range of resonance frequencies of transducer high Q-factor: narrow band-width => ideal transmitter low Q-factor: wide band-width => ideal receiver
Intensity output energy of transducer (< 100mW/cm²) proportional to square of wave amplitude
Coarse gain overall amplification of all received echoes Near gain reduces intensity of echoes near the transducer
Far gain amplifies distant echoes
Enhancement amplification of echoes from a selected depth
Time gain control although displayed as a line is an exponential correction of the expected attenuation and calculated
according to the time required for the echo to return to the probe basis for enhancement after fluid filled spaces, i.e. in cysts less attenuating than calculated, deeper tissue “unnecessarily” enhanced
Delay tissue depth from which TGC becomes effective
Reject filter for low amplitude echoes, reduces noise similar to pulse height analyser in γγ-camera
Frame rate, FR number of new images acquired per second
Doppler Doppler-shift (F0 = incident frequency, v = velocity of reflector, c = speed of sound in medium,
α = incident angle between beam and moving object)
∆FF v
c=
⋅ ⋅ ⋅2 0 cosα
Continuous wave doppler, CWD
one transmitter, one receiver crystal, axes intersect in focus no depth resolution
Pulsed doppler depth resolution via “range-gating” = transducer receives only for a short period of time delay to reception determines depth of sampling time span of sampling determines gate width
Colour doppler multigated throughout slice => real-time two dimensional imaging Power doppler Pulse repetition frequency, PRF
limited by time required for most distant echoes to return = time of flight, TOF max. achievable depth = ½ TOF maximum frame rate = PRF/lines of frame aliasing occurs if PRF < x2 doppler-shift = Nyquist-limit
Artefacts in ultrasound Multiple reflections returning signal is partially reflected from surface of probe acting as a further primary pulse of
weaker intensity. This gives “ghost” echoes at multiples of the original transducer-interface distance Acoustic shadows at interfaces with high degree of reflection Acoustic enhancement artefact of time-gain-control after areas of low attenuation
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Reverberation echoes reflected echo is reflected back against original object by scatterer from where it is again reflected back to the probe. This creates an apparent more distant echo from a non-existing structure
Doppler artefacts Compound artefact CWD has no depth resolution => if more than one vessel within line of beam, detected doppler shift
is averaged Mirror image doppler unable to determine direction of flow if angle between beam and reflector » 90° Aliasing pulsed doppler artefact
if the detected doppler shift frequency becomes large (cos α large, incident angle shallow) compared with the pulse repetition frequency, the machine has increasing difficulties determining the direction of flow => colour spectrum is wrapped around giving mixed blue and red signals remedial action: increase repetition frequency, decrease angle of probe Fpulse rep. should be at least twice the detected doppler shift·(∆F)
Biological effects of US 1. tissue heating: not noticeable in diagnostic range 2. streaming: creation of flow along beam and back in perimeter, affects cell membrane permeability, proportional to
intensity 3. cavitation: interaction with microbubbles within tissue
1. stable cavitation, oscillating of bubbles 2. unstable cavitation, bubbles increase in size until they implode with temperature rise to hundreds/thousand degrees happens with high intensities (> 100 mW/cm²) at low frequencies
4. vibration, pressure changes, etc.
MAGNETIC RESONANCE IMAGING, MRI
Protons precess at Larmor frequency ω in magnetic field of strength B; γ = gyromagnetic ratio
ωωL = γγ·B0 ~ 43 MHz for 1 Tesla, ~ 64 MHz for 1.5 Tesla spin-up protons precess in opposite direction as spin-down protons Tesla = strength of a magnetic field = 10,000 Gauss Tesla, Nikola (1856-1943) Croatian-American inventor of the high-frequency generator (1890), a radio transformer called the Tesla coil (1891), and father of the electromotor (1893). Ratio of protons in low-energy (spin up) to high-energy state (spin down) is described by the Boltzman distribution (approx. 10.000.001 : 10.000.000 for diagnostic field strength))
B-field produced by superconducting electro-magnet cooled to 4° K by liquid helium and nitrogen. strong field, homogenous, but expensive and sensitive to Eddy-currents quench = warming of the coil usually due to escaping coolant and destabilisation of field
RF-pulses generated and received by coils - volume coil surrounds patient, major transmitter, receiver for large parts - gradient coils slice selection, frequency and phase encoding; vibrate with sequence repetition - surface coils anatomically shaped receiver coils for smaller anatomy: head, shoulder, breast head coil = transmit / receive coil - shim coils adjust field inhomogeneities
Nuclear angular momentum
dependent on whether number of nucleons even or odd =0 for even numbers => protons do not precess
Slice selection gradient modifies the strength of the longitudinal field B
0 by ± 8-10% during the application of the RF- / rephasing
pulse. Thus different planes of the body are given different resonance frequencies ωL.
Slice thickness is determined by a. bandwidth of RF-pulses and therefore the bandwidth of Larmor-frequencies covered. b. steepness of gradient field and therefore distribution of resonance frequencies through the body
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Phase encoding gradient Prior to acquisition a vertical gradient is applied for a short period of time until protons at different height in the slice have lost phase coherence. When gradient is removed, the protons precess at the same frequency again, but are out of phase. => spatial resolution along the y-axis
Frequency encoding gradient = “read-out gradient” after all protons in the same slice have all been excited to precess at the same frequency a transverse gradient is applied during acquisition which alters ω
L and therefore the emitted signal frequency of the individual protons
across the slice => spatial resolution along the x-axis
Frequency- and phase encoding can be performed in any of the three axes, the long axis of the image is usually frequency encoded
All signals throughout the slice vary in frequency, phase or both. After Fourier transformation they can be assigned to a specific location in the slice
Signal-to noise ratio
improved by lengthening TR and shortening TE => reduction in contrast
Resolution improved by reduction in voxel size: 1. reduction in slice thickness (reduced partial voluming) 2. reduced field of view 3. increased matrix
Field of view, FOV large FOV results in larger voxels (larger blocks of tissue per pixel) => reduced noise, but also reduced spatial resolution
Matrix fine matrix = smaller pixels => more noise, but increased spatial resolution as spatial frequencies reduced
T1 spin-lattice-relaxation
time required to regain 63% of the original longitudinal magnetisation after 90° RF-pulse, measured by tilting recovering vector into horizontal plane by second 90° pulse
T2 spin-spin-relaxation loss of phase-coherence of transversal magnetisation after spins have been put in phase by 90° pulse, time required for transverse signal to decay to 37% in T2 weighted sequence external effects on decay are neutralised by repeated 180° pulses which revert spin; T2 curve connects points of maximum transverse signal when phase coherence has reoccurred
T2* loss of phase coherence through internal and external effects, far shorter than T2 TR time to repetition, interval between pulse sequences TE time to echo, interval between initial phasing pulse and signal acquisition in T2-sequence, rephasing 180° pulse
at TE/2 TI inversion time, in inversion recovery (as for T1 sequence, only initial pulse flips longitudinal vector 180°, before
recovery starts) interval between 180° inversion pulse and 90° pulse for measurement
values [ms] short medium long TR <500 1000 >2000 TE 20 60 >80
Sequences:
Spin echo 90° pulse - decay of phase coherence / lateral magnetisation - 180° rephasing pulse
- acquisition of echo after TE for T2 signal intensity = retained transverse magnetisation when spins in phase again at TE (= TE/2 after rephasing pulse) if T2 of tissue long => high signal (slow decay) - T1 measurement after TR with repetition of sequence signal intensity = recovered longitudinal magnetisation if T1 of tissue short => high signal (quick recovery) TR and TE short for T1-weighting TR and TE long for T2-weighting
Proton-density/ long TR, short TE => T1 and T2 effects eliminated
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saturation recovery => signal only dependent on proton density Partial saturation 90° pulse - after short TR repeat 90° pulse for acquisition recovery T1 weighted Inversion recovery 180° pulse inverts longitudinal magnetisation - recovery - spin echo sequence
heavily T1 weighted if acquisition takes place when one particular tissue has got no longitudinal magnetisation, this gives no signal
STIR short T1 inversion recovery, fat suppression acquired when transverse magnetisation of fat has recovered to 0°
FLARE fluid attenuation recovery, fluid suppression Gradient echo fast sequence
1. initial transverse pulse at small flip angle (<45°, short duration of pulse), thus leaving fair amount of residual longitudinal magnetisation for early 90° acquisition pulse => 2. TR very short (rate-limiting step in T1-weighting), the longer TR, the more T1 weighted is the scan 3. external effects reinforced by applying gradient B-field into B0 at TE/2 => strong T2*-effects (fast spin dephasing), rephasing by inversion of gradient and acquisition at TE when spins in phase again
For total duration of sequence TR of major importance. Short scan times achieved by
- Gadolinium => shortens T1 - multi-slice-imaging => RF-pulses for subsequent slices are triggered during TR of first slice (which is set slightly longer) - gradient echo => a. smaller flip angle b. acquisition with magnetic gradient is faster than 180° rephasing pulse in spin-echo c. T2* effects work quicker than T2 effects
Contrast media ferromagnetic unsuitable, as particles acquire and retain large magnetic moments once introduced into B-field paramagnetic positive CM, increase local field strength, shorten T1
Gadolinium 15764 Gd rare earth lanthanide, used in chelated form as dimeglumine-gadopentate, Gd-
DTPA (diethylene-triamino-penta-acetate) = soluble for iv use dose: 0.2 ml/kg, max. dose 20 ml, 80% excreted renally within 3 h side-effects much rarer than with non-ionic CM CI: haemolytic anaemias, pregnancy fatty oils for oral use
superparamagnetic negative CM transient large magnetic moments, disrupt local magnetic field, enhance spin-spin effects and shorten T2 ferrite colloids Ba-sulphate
Artefacts chemical shift due to different binding of protons in fat (C-H) and water (O-H) the Larmor frequency of these tissues differs
by approx. 100-250 Hz, which simulates a different spatial resolution in the direction of the frequency encoding gradient => dark band at the fat / water interface insignificant for B0=0.5 T
avoided by reduced field strength B0 reduced filed of view (FOV) = increased pixel size increased receive band width to include difference in frequencies
susceptibility changes in local field strength through paramagnetic effects
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NUCLEAR MEDICINE
Decay constant Residual radioactivity
λ =0 693.
t½ A A e t= ⋅ − ⋅0
λ
COSH-regulations for occupational medicine apply for handling of isotopes The Gamma Camera for good images the total number of counts required is 300-500 kilocounts (kcts) for small images, up to 1 Mct for large images spatial resolution ~ 1cm Collimator similar to secondary radiation grid, but main function is to allow spatial resolution as gamma rays emitted in
all directions, not only perpendicular to the crystal as photons are emitted in all directions as well as scattered, collimators required for spatial resolution by absorbing scatter trade-off between sensitivity and resolution, sensitivity usually < 1% - parallel hole collimator commonest - pinhole collimator for thyroid and other small objects, produces inverted and enlarged image (camera obscura) problems with distortion of structures from different planes - diverging collimator diverges towards patient, for large areas, reduces field of view - converging collimator diverges towards camera, enlarges image, significant distortion
with modern large field g-eras diverging (and converging) collimators only rarely used (distortion!)
examples of parallel hole collimators (40 cm crystal) No. of holes hole diameter septal thickness low energy, high resolution, LEHR 30.000 1.8 mm 0.3 mm low energy, general purpose, LEGP 18.000 2.5 mm 0.3 mm low energy, high sensitivity, LEHS 9.000 3.4 mm 0.3 mm medium energy, high sensitivity, MEHS 6.000 3.4 mm 1.4 mm LEGP for standard bone scan, LEHR for smaller FOV like pelvis/THR
Crystal NaI (high density, z=32) with Tl impurities (1 ppm) to increase sensitivity, 1-2 cm thick, sensitive to
mechanical and thermal shock impurities influence wavelength of emitted light 80-90% of incident photons are absorbed 10% are converted to light at a ratio of 1:1.000 - 1:4000 (reduced absorption for energies > 200 keV) emitted γγ-radiation is monoenergetic and specific for isotope spatial localisation along x- and y-axis dead time ~ 0.2 µs => max. temporal resolution = 500 kcts/sec, but temporal resolution of electronics much smaller => limiting factor
Sensitivity proportion of incident gamma photons that produce a scintillation event
PM-tubes photocathode (borosilicate) converts light photons into electrons, accelerated towards anode in a zig-zag fashion hitting several dynodes in the process and liberating further electrons => amplified electrical impulse height of impulse (= z-vector) proportional to energy deposited in crystal hexagonal shape allows denser packing of tubes
Pulse height analyser
electronic filter, determines whether recorded pulse produced by isotope, background, scatter or other artefact, used to differentiate between different isotopes
Energy window range of energies that are included in image acquisition
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Resolution a. spatial ≥ 1 cm b. temporal ≤ 50 - 60 kcts/s
c. energy via pulse height analyser, approx. 12% at 140 keV
Uniformity integral uniformity = variation from the mean number of counts over a defined area
Linearity degree of correct spatial resolution, i.e. how well the correct origin of the signals are being recognised
Inhomogeneities collimator, computer
Single photon emission tomography, SPECT better sensitivity, resolution and speed than γγ-camera attenuation correction
photons emitted from centre of slice more attenuated than from superficial voxels this is corrected for before backprojecting (pre-processing) by multiplication factors this is not required for lung-scans
Isotopes za X
elements are described by their mass number a and their atomic number z a denotes the (average) molecular weight, i.e. the number of nucleons (neutrons and protons) z equals the amount of protons within the nucleus and therefore the number of electrons in the shell The physical weight is dependent on a, the chemical properties on z Isotopes are elements with the same z, (i.e. the same chemical properties) but different molecular weight => they differ in the number of neutrons
Technetium 4399Tcm
most frequently used isotope with ideal properties - pure γγ-emitter - ideal emitted energy (140 keV) => low patient dose, within range of scintillation crystals - half-life (6 hrs) roughly as long as examination time - easy production => generator - good biochemical and pharmaceutical properties
ion form as sodium-pertechnetate (TcO4-) behaves similar to Cl
- ions
Tc-generator:
99 Mo (t½ 68 hrs) on Al column, ß-decay to metastable
99m Tc which is eluated with NaCl
weekly replacement, maximum yield 22 hrs after previous elution liquid Tc can be disposed of into drains, less than 30% of administered dose become waste Hospitals may dispose up to 1 MBq/day without notification
Half-life, t½ time required for activity to reduce by 50% 1. Physical half-life = actual radioactive decay 2. Biological half-life = pharmacokinetics, excretion
Effective Half-life
1 1 1t½ t½ t½eff phys bio
= +
Chemical purity proportion of desired isotope of all contained substances, i.e.
99m Tc : NaCl
Radiochemical purity proportion of the isotope in its desired form, i.e. 99m
Tc : 99
Tc Radionuclide purity proportion of the desired isotope of all radioactive isotopes in the preparation, i.e.
99m Tc :
99Mo
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production t½ emission / keV stable product use 67
Ga cyclotron 72 h γ 92, 182, 300 WCC-scan 111
In cyclotron 67 h γ 171, 245 WCC-scan 123
I cyclotron 13 h γ 159 kidney / thyroid 201
Tl cyclotron 73 h ß, γ 80 cardiac scan 113m
In
generator 100 h γ 392
113 Sn
81m Kr
81 Rb-generator 13 sec γ 190 ventilation scan
99m Tc
99 Mo-generator 6 h γ 140
99 Tc
127
Xe 36 days γ 172, 203, 375 ventilation scan
133 Xe nuclear reactor 5 days ß, γ 81 ventilation scan
131 I nuclear reactor 8 days ß, γ 360 thyroid ablation
free pertechnetate behaves like Cl- => accumulation in gastric mucosa and salivary glands
Tests & Radiopharmaceuticals Kidney a. dynamic
99mTc-MAG-3 (mercapto acetyl triglycerine) 75-100 MBq
tubular secretion quick, sensitive, not cheap 99m
Tc-DTPA (diethylene triamino pentaacetic acid) 150-300 MBq glomerular filtration cheap, not as sensitive as MAG-3 123
I-hippuran (glomerular filtration and) tubular secretion 20 MBq expensive, cyclotron-produced
b. static 99m
Tc-DMSA (2,3-dimercapto succinic acid) 80 MBq tubular absorption, retained in renal cortex 99m
Tc-glucoheptonate 300 MBq glomerular filtration and tubular secretion, cortical retention worse resolution, but smaller dose than DMSA
Bone
99mTc-MDP (methylene-diphosphonate), EDE 3-4 mSv 500-600 MBq
phosphate analogue, binds to bone, rapid (renal) clearance from other tissues => renal imaging possible image acquisition 3-4 hrs post-injection when diphosphonates integrated into bone and soft tissue activity has cleared NB: increased speed of uptake in abnormal bone uptake into muscular damage/calcification (trauma, surgery, im-injections) shin-splint uptake in periosteal reaction (stress in the growing tibia) superscan: diffuse metastatic disease, all activity immediately taken up by bone, no background or renal activity, virtually pathognomonic for Ca-prostate (other malignancies don not get that far) 3-phase-scan for hyperaemia (infection, tumour) 1. arterial blood flow, immediate dynamic scan 2. blood pool / equilibrium after several minutes, soft tissue hyperaemia 3. delayed static scan > 4hours
Heart myocardial perfusion,
201TlCl
3-5 % deposited within myocardium, dependent on blood flow and Na/K-pump distribution heart : lung > 2.5:1 patient fasted (exercise!), post-exercise images can be obtained without further injection
Liver
99m Tc-labelled colloids iv 70-80 MBq
=> phagocytosed in reticulo-endothelial cells (15% of liver cells = Kupffer-cells) demonstration of liver (75% of activity), spleen (15%) and bone marrow (10%) Ind.: tumours, chr. liver disease 99m
Tc-IDA ( imino-diacetic acid) derivates 75 (-150) MBq behaves like bilirubin, selective uptake by hepatocytes, secreted into bile, concentrated in gallbladder Ind.: biliary atresia and obstruction, biliary leaks/anastomoses post-surgery, cholecystitis
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Lung EDE 1-2 mSv, dose to foetus ~ 0.2 mSv Ventilation: 81m
Kr gas: room air pumped through generator 2000 MBq t½ = 13 s => tidal breathing performed simultaneously with perfusion scan as higher energy (192 keV) than Tc, but for each position the perfusion image is acquired first to avoid cross-talk from down-scatter, activity decays in between repositioning lateral views useless due to high energy and penetration 99m
Tc-DTPA aerosol, cheap and easy 80 MBq separate* from perfusion-scan as same isotope, CI: COAD 99m
“Technegas” 20 MBq carbon electrode boiled off in Ar / Tc filled chamber => Tc-labelled C-particles, deposited in alveoli, => alveolar ventilation CI: COAD separate* from perfusion-scan * if Tc used for ventilation scan, perfusion scan possible directly afterwards, if MAA dose increased x5
127
Xe gas needs high energy collimator, exhaled gas must be collected 133
Xe gas ß-emitter => high dose, low energy => must precede perfusion scan exhaled gas must be collected Perfusion: 80-100 MBq Tc-labelled albumin-macroaggregates (10-90 µm) or -microspheres (20-30 µm) occlude < 1% of pulmonary capillary bed with 95% deposition in lungs
Parathyroid Tc - Tl subtraction scan uptake of
201 TlCl thyroid and parathyroid = mask < 80 MBq = ~ 10 mSv
selective thyroid scan with Tc subtracted < 80 MBq = ~ 1 mSv
Thyroid 99m
Pertechnetate, EDE 2.5 mSv 60-80 MBq behaves similar to iodine => trapped in thyroid, but not organified target : background = 10 : 1 (4:1 in salivary glands) pinhole collimator !
123 I, given as a drink orally (NaI) 20 MBq
concentrated in thyroid > 3-4 hrs, better images, but higher dose than Tc
Inflammation 67
Ga-citrate, iv 150 MBq high dose, no preparation required, three different energies can be imaged highly protein-bound (esp. transferrin), normal uptake in RES and salivary/lacrimal glands excreted mainly into bowel => high activity up to 72 h radio-labelled white cell scans leucocytes harvested from patient, separated, labelled and reinjected minimum WCC 2.000/µl, donor cells can be used 111
In 20 MBq 99m
Tc - HMPAO (hexamethyl-propylene-amine-oxime) 200 MBq
Tumours phaeochromocytoma, carcinoid, medullary Ca. thyroid and other APUD tumours, neuroblastoma
123 I - MIBG (meta-iodo-benzyl-guanidine) 250 (-400) MBq
131 I - MIBG, cheaper and better available, but higher dose and inferior images 20 MBq
acts as noradrenalin-equivalent, antidepressants and sympathomimetics (nose drops!) must be stopped thyroid blockade with NaI or Lugol’s solution slow iv-administration
Brain a.
99m Tc - glucoheptonate } 500 MBq static
b. 99m
Tc - DTPA } 800 MBq dynamic similar properties, cross damaged blood-brain-barrier only, lower noise due to faster clearance than pertechnetate static images after 1-2 hrs => in normal brain remaining activity in non-neural tissue and vessels
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c. 99m
Pertechnetate 1000 MBq accumulates in choroid plexus, salivary glands and thyroid
Anatomical markers
wands with radio-active tip flexistrips 60
Co-point sources
RADIATION PROTECTION Primary effects of x-rays
- ionisation 35 eV required to produce one ion pair => one 70 keV photon produces 2000 ion pairs - heating (negligible)
Secondary effects - physical: fluorescence (immediate, < 10 µs), phosphorescence (delayed), thermoluminescence (on heating) - chemical: redox-reaction, i.e. x-ray film - biochemical: destruction of enzymes through free electrons - biological: inactivation of bacteria
slow moving electrons ionise more
Bragg-curve: relative ionisation as a function of the distance travelled in air
Minimal focus-skin distance 30 cm, recommended 45 cm 60 cm for thorax (lungs)
Measurement of radiation Measurements in air, as 1. cheap and ubiquitous 2. constant composition 3. atomic number of air (7.6) very similar to soft tissue (7.4) but lower density requires relation to unit mass and the use of mass attenuation coefficient rather than linear attenuation coefficient. Radiation exposure, X total charge (amount of ion pairs) produced per unit mass [C/kg]
1 Roentgen = 2.58·10-4
C/kg
XQm
=∆∆
Exposure rate exposure per unit time [C/kg·s]
XXt
•
=∆∆
Absorbed dose, D energy deposited per unit mass [J/kg = Gray, Gy] Dose rate dose per unit time [Gy/s] Equivalent dose, H absorbed dose corrected for relative biological effect by specific weighting factor
H= WR x D [J/kg = Sievert, Sv] exam dose equivalent Ba-enema 8 CT-chest 8 Ba-meal 5 IVU 4 lat. lumbar spine 2-3 VQ-scan 1-2 Tc-thyroid scan 0.5 chest pa 0.04 extremity 0.01
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Relative biological effect, RBE
correcting factor WR for different types of radiation, compared with biological effect of 200 kV x-rays x- and γγ-rays 1 ß-particles 1 protons > 20 MeV 5 neutrons 5-20 α-particles 20
Effective dose, E total sum of the fractional doses each organ has received during the exposure to radiation
E = Σ (H x WT)n [Sv] the organ doses are individually weighted according to the relative sensitivity of the organ (tissue weighting factor WT) organ WT
skin, bone 0.01 bladder, breast, thyroid 0.05 liver, oesophagus, other stomach, colon 0.12 lung, red bone marrow female breast 0.15 gonads 0.2
Dose and dose rate effectiveness factor, DDREF
biological effects of radiation at lower doses uncertain, assumed to be higher => correction factor for extrapolation x2 for doses < 0.2 Gy ? >2 for doses < 0.05 Gy
Collective dose dose to a population [man Sv]
= average effective dose to individual x number of individuals
Dose-area-product, DAP absorbed dose in air (averaged over beam area) x area of beam [cGy/cm²] independent of distance to tube, measures tube output, does not take geometry and nature of exposed parts into account guideline for exposure during examination used as dose measurement by NRPB
DAP-meter air ionisation chamber mounted onto exit window of x-ray tube Linear energy transfer, LET
measure of energy deposited per distance travelled in tissue [keV/µm] radiation energy LET
x-/γγ-rays 1 MeV 0.5 x-/γγ-rays 100 keV 6 ß-particles 20 keV 10 neutrons 5 MeV 20 α-particles 5 MeV 50 if LET high, likelihood of multiple DNA-breaks is high for low LET-radiation this is increased by a high partial pressure of O2 and reduced by sulfhydryl- and ethanol-groups (antioxidants garlic and alcohol)
Air Kerma Kinetic Energy (of electrons) Released per unit Mass of Air, [Gy]
if Kerma high => production of secondary Bremsstrahlung, not accounted for in calculation of absorbed dose
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Several phases for conduction of electricity through a gas: 1. with increasing voltage ions move to electrodes, current proportional to field strength 2. 1st plateau, all prevalent ions are being collected 3. further increase of current with field strength as secondary ionisation occurs, current still proportional to field 4. Geiger-Müller plateau, increase in discharge no longer proportional to increase in voltage 5. continuous discharge
Ionisation chambers “air-equivalent walls”, contains Xenon (inert, high atomic number => many interactions) at high
pressure, secondary electrons produced in wall ionise gas can measure rate, as current proportional to number of ionizations
Geiger-Müller-counter glass tube filled with nobel gas (Argon) at low pressure with added alcohol for quenching
fine central wire acting as anode, potential 300-400 V long dead-time between detections, ~300µs detects x-rays as well as ß-particles simple, cheap, compact, sensitive, unspecific good detector of radiation activity but unsuitable for monitoring rate or dose
Film-badge dosemeter double sided emulsion of different speed (back = slower)
fast emulsion used for doses < 100 mSv, slow emulsion < 10 Sv (!) for high doses the (completely blackened) fast emulsion is stripped off for evaluation different filters allow energy resolution
sensitive range: x-rays 10 keV-2Mev, β-particles 500 keV-3.5 MeV, sensitive to neutrons filter attenuation air-window α-particles (in film wrapping) thin plastic (50g/cm²) low energy β-particles thick plastic (300g/cm²) low energy x-rays, most β-particles Dural (Al-alloy, 1mm) x-rays < 65 keV, all β-particles Sn (0.7mm)-Pb (0.3mm) x-rays < 75 keV Cd (0.7mm)-Pb (0.3mm) converts thermal neutrons to x-rays => film blackening developed at specialist centres together with films from the same batch exposed to a standard γγ-emitter
Scintillation counter NaI-crystal up to 2.5 cm thick requires light-proof envelope sensitive to thermal and mechanical injury photomultiplier tube required (series of dynodes along 1200 V)
Thermo-luminescent dosemeters, TLD
usually LiF, CaSO4 for low energies electrons captured in electron traps (impurities) in forbidden band after irradiation are only released when heated to 300-400° C except for some low temperature peaks which are released spontaneously within 24-48 hrs => TLD’s left for 2 days prior to processing (= fading) + small and easy to use + emitted light practically proportional to absorbed dose + high sensitivity + sensitivity independent of radiation dose and energy + stored information stable for a long time + re-useable after “annealing” - require careful calibration - careful annealing required to maintain constant properties
classified person occupational exposure > 0.3 of limit, i.e. 15 mSv/a supervised area dose rate 2.5 - 7.5 µSv/h controlled area dose rate > 7.5 µSv/h (> 300 µSv/wk)
clearly marked, physically demarcated, access restricted to patients and qualified personnel, volatile as only exist when mains switched on - access for unqualified personnel out of hours
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Background radiation 2.5 mSv/year, (3-5 cGy in 30 years) responsible for 10% natural mutations and neoplasms
Natural sources 87% (=> 50% radon) Medical 12% “civilisation” < 1% (air travel, watches etc.) > military fallout > occupational > nuclear industry
main contributors to medical background: examination contribution to total examinations contribution to background CT 2 % 20 %
L-spine 3.3 % 15 % Ba-enema 0.9 % 14 % Ba-meal 1.6 % 12 % IVU 1.3 % 11 % CXR 25% 2 %
increased risk of dying from a cancer caused by exposure to ionising radiation = 70 per mSv majority of genetic mutations are not related to radiation effects
Stochastic effects Non-stochastic effects not dose-dependent dose-dependent linear increase of incidence with dose non-linear increase of severity with dose (= probability of developing effect) accepted threshold 150 mSv 1. somatic effects leucaemia erythema, necrosis, infertility neoplasms bone marrow suppression death 2. Genetic injuries ------- affect future generations chromosomal abnormalities
Dose Limits (ICRP, IRR 85) => non-stochastic effects should never occur Occupational trainee < 18 years Gen. public [mSv / year ] Whole body 50 15 5 extremities & individual organs 500 150 50 lens of eye 150 45 15 pregnant abdomen (total dose during pregnancy) 2 women of child-bearing age -- 13 mSv / 3 months occupational dose limit 50 mSv / year => 1mSv / week (2 weeks holiday) => 25 µSv / hr (40 hrs/wk) expected to be dropped to 20 mSv/a, ICRP 60 from IRR 1990 awaited NB: currently no total dose limits for patients => ALARP, NRPB has published lists of British averages and recommended max. doses Absorbed dose rate at the skin for fluoroscopy < 0.01 mGy/min Average additional effective dose from occupational exposure [ mSv / year ]
nuclear industry, air crews 2 mSv miners, industrial radiology 1 mSv medical/dental/veterinary staff 0.25 mSv additional background in Cornwall 5 mSv
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Threshold doses for non-stochastic effects on individual organs (single dose) [mSv] temporary blood film changes 200 hair loss 500 bone marrow suppression 500 skin erythema 2,000 bone marrow ablation 2,500 dermatitis, ulcerations 5,000 conditioning for BMT 10,000 temporary infertility (men) 150 lens opacities 500 - 2,000 sterility (testes/ovaries) 3,000 - 6,000 cataract 5,000 LD 50 3,000 - 5000 mSv National radiation protection board, NRPB National level, basis for UK ionisation radiation legislation
- national protocol for patient dose measurements in diagnostic radiology July 1992 - patient dose reduction in diagnostic radiology - guidelines on MRI and USS as alternatives to radiographs - radiation protection of pregnant women
report R 200 table of average British radiation doses for individual examinations 75th percentile of nation wide DAP-measurements aimed as maximum dose for particular exam (generous!) Ba-enema 6,000 cGy/cm² IVU 4,000 cGy/cm² Ba-meal 2,500 cGy/cm² L-spine 1,200 cGy/cm² abdomen 800 cGy/cm² pelvis 500 cGy/cm²
20 % of requested investigations do not contribute to clinical management Radioactive substances act 1993 , RSA (Her Majesty’s Inspectorate of Pollution, HMIP) a. certificate of registration
identify site, type, amount and purpose of substances, person responsible b. certificate of authorisation for accumulation / disposal of radioactive waste The medicines (administration of radioactive substances) regulations 1978, MARS (Dpt. of Health) prohibit administration of radioactive substances except by doctor/dentist holding ARSAC-certificate or by a person under directions of such a doctor ARSAC = administration of radioactive substances advisory committee
certificate specifies substances and site on which administered copy of certificate to radiation protection advisor
enforced by Medicines Control Agency International Commission on Radiation Protection and ionising radiations regulation (Dpt. of Health) Basic philosophy 1. Justification
2. Optimisation = ALARA 3. Limitation
ICRP 26 (IRR 1976) basic guidelines for staff protection under current legislation ICRP can recommend only, legislation founded on “Health and Safety at Work” act 1974 IRR 85 legally binding guidelines for the protection of workers against ionising radiation resulting from work activities => approved code of practice employers are responsible for - restriction of occupational exposure,
- appointing radiation protection advisors, RPA - safe equipment / protective equipment - ensure dose limits are not exceeded - definition and demarcation of controlled areas, access restriction - inform Health and Safety Executive, HSE of accidental over-exposure - keep documentation over 50 years
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employees obliged to - follow guidelines, not expose themselves or others unnecessarily
- use protection - report faults in diagnostic and protective equipment - notify employer of over-exposures
The approved code of practice, ACOP (IRR 1985) • employer has the overall responsibility • radiation protection advisor, RPA
physicist with minimum 6 years experience, to ensure work is in accordance with the regulations needs to be informed in the event of accidental over-exposure
• radiation protection supervisors, RPS in individual x-ray departments responsible to superintendent radiographer, should ensure that everybody is in possession and familiar with the relevant part of the local rules, as well as obeying them needs to be informed about pregnant workers
• demarcation of controlled areas • guidelines for mobile units
controlled area: 2 m around unit, 3 m in theatre in direction of primary beam fluoroscopy: 2 m chest and extremity work 5 m other and theatre to attenuating wall or backstop
• elective radiography (incl. abdomen) of women of child-bearing age within 28 days of last period • equipment checks, providing of protective equipment • procedures for accidental over-exposure • framework for local rules
IRR 1988: Protection of persons undergoing medical examination or treatment, POPUMET
regulation 2: - guidelines for physical and clinical (ARSAC-holder) direction of medical exposures - local guidelines regulation 3: - regulations do not apply to scientific research regulation 4: - dose limitation, ALARP - responsibility with the physically and clinically directing individual => criminal prosecution regulations 5-8: - adequate training, core of knowledge regulation 9: - detailed records of equipment regulation 10: - employer needs to provide services of adequately qualified (min. six years) physicist regulation 11: - local rules (apply for x-ray dept. only, nuclear medicine dealt with by MARS and RSA) regulation 33: - criteria for notification of accidental overexposure fluoroscopy x3 } mammography/abdo/pelvis/lumbar spine x10 }intended dose chest/skull/extremities/dental x20 }
enforcement by POPUMET inspectors
The ionising radiations (outside workers) regulations 1993 protection of classified personnel employed temporarily on other sites UK investigation limit: 15 mSv/a, 75 mSv/5aa
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ANATOMY
The Skeleton Synovial joints costo-transverse joints
sacro-iliac joints (upper 2/3) median atlanto-occipital joint incu-stapedial joint
Spine all cervical vertebrae have transverse foramina, but vertebral a. usually enters C6 or higher
C2/3-6 usually bifid spinous processes ant. spinous ligament stronger than post., both adhere to discs, the ant. to a degree to the vertebral bodies, not the post. as it has to pass over basivertebral veins T3 smallest thoracic vertebra spina bifida occulta ~ 10% sacralisation of L5 ~ 5%
Calcification in membrane Calcification in cartilage clavicle, first bone to calcify, from 6/40 scapula flat bones of the skull, skull vault sphenoid, ethmoid mandible
Appearance of primary ossification centres wrist 1. capitate 2-3 months
2. hamate 3 months radial epiphysis 1 year 3. triquetral 2-3 years 4. lunate 3 years 5. trapezium 3-4 years 6. trapezioid 4 years 7. scaphoid 4-5 years ulnar epiphysis 6-7 years 8. pisiform 8-9 years
Bone age scores a. Greulich & Pyle, comparison with standardised hand x-rays b. Tanner & Whitehouse, 20 bone score, carpal score, etc., point score for individual bones
elbow C capitulum humeri 6 months Come left elbow (years)
R radial head 5 years Rub I (6) E (11) I internal (ulnar) epicondyle 6-7 years My T (9) C (0.5) T trochlea 9 years Tree O (10) R (5) O olecranon 9-10 years Of E external (radial) epicondyle 10-11 years Love
shoulder med. humeral head 3 months
coracoid 6-12 months, fuses at 15, calcification begins in utero from 8/40 lat. humeral head 1-2 years greater tuberosity 3 years lesser tuberosity 5 years
sternum fusion of sternebrae by 25 years
fusion of xiphoid by 40 years knee femoral epiphysis in utero, 36/40
tibial epiphysis in utero, 38/40 fibular head 4 years patella 4 years
ankle calcaneus in utero, 26/40 talus in utero, 28/40 tibial epiphysis 6-8 months fibular epiphysis 10-12 months
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foot cuboid at birth
lateral cuneiform 3-6 months medial cuneiform } interm. cuneiform } 2.5 years navicular }
Arterial System Aorta abdominal aorta
1. four unpaired branches coeliac axis, sup. & inf. mesenteric aa., medial sacral a. 2. three paired visceral branches middle suprarenal aa. T12, renal aa. L1, gonadal aa. L2 3. parietal branches inferior phrenic aa. T12, subcostal aa., lumbar aa. x4 diameter: root 4.5 cm ascending aorta 4 cm descending aorta 3 cm abdominal aorta 2 cm bifurcation: body L4 60% below 30%
Coeliac trunk arises upper body of L1 in 50%, higher in 45%
in abnormal configurations the coeliac trunk is defined as the trunk out of which two out of the following four vessels arise: 1. left gastric a. } 2. splenic a. } usual configuration 3. common hepatic a. } 4. superior mesenteric a., SMA
normal variants: - replaced right hepatic artery from SMA 20% (if only one segment supplied from SMA it is usually segment 6) - replaced common hepatic artery from SMA 5% - left hepatic artery or branches from left gastric 10% (all variants) - splenic a. from aorta 0.5% common hepatic a. 0.5% left gastric a. 1% common coeliac and SMA 0.5%
Superior mesenteric artery, SMA arises lower border L1, 6mm below coeliac axis
Inferior mesenteric artery, IMA Venous system few valves in ascending veins
one valve proximal to junction of long saphenous and femoral in 70% no valves proximal to inguinal ligament in 25%
Skull The sphenoid ridge with the ant. clinoid processes forms the anterior border of the middle cranial fossa, the petrous ridges with dorsum sellae and post. clinoid processes form the posterior border. The anterior and posterior cranial fossae lie anteriorly/posteriorly to these boundaries. Anatomical lines:
Chamberlain’s hard palate - sup. edge of occipital bone at foramen magnum McGregors hard palate - inf. edge of occipital bone at foramen magnum, more reliable
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basal invagination if odontoid peg extends > 2 mm / 5mm above it (?name) sphenoid tuberculum - int. occipital protuberance, crosses fourth ventricle Basal angle angle between lines from tuberculum sellae to nasion and basion (= plane of clivus) platybasia if > 145° (normal 125°-142°)
Foramina optic II, ophthalmic a. and v. rotundum V b }anterior to posterior ovale V c, access. meningeal a. (maxillary a.) }in major wing spinosum a. meningea media (maxillary a.) }of sphenoid bone lacerum cartilage between sphenoid and occiput jugulare ant.: IX, inf. petrosal sinus between petrous bone and occiput post.: X + XI, bulbus v. jugularis inferior to int. audit. meatus mastoid emissary vv. hypoglossal canal XII occipital bone
Fissures sup. orbital III, IV + VI, V1 sup. ophthalmic vv. ⇔ angular vein inf. orbital zygomatic nerve => infraorbital n. infraorbital a. from maxillary a.
Sutures normal width 10-15 mm at birth
3 mm at 12 months 1 mm at 2 years mendosal horizontal between limbs of lambda usually gone after 1 year separates intraparietal from supraoccipital portion of occipital bone metopic ant. extension of sagittal suture usually gone at 2 years persists in 10 - 20% spheno-occipital synchondrosis closes at puberty bregma junction of coronal and sagittal suture lambda junction of sagittal and lambdoid suture asterion junction of squamosal and lambdoid sutures pterion junction of coronal, sphenofrontal, sphenosquamosal and squamosal sutures
Frontal
Bone
Sphenoid
Bone
Parietal Bone
SquamousTemporal
Bone odontoid peg fuses with axis from 7 years
Fontanelles lateral closes at 6 months posterior closes at 9 months anterior closes at 18 months
Craniostenosis = cranial deformation due to premature closure of sutures growth perpendicular to suture stops and compensatory growth in direction of synostosis takes place
Scaphocephaly sagittal suture, reduced lateral / excessive ap growth => narrow, long skull commonest form, boys > girls
Brachycephaly coronal suture, reduced ap / excessive lateral growth => tall, wide skull if unilateral mainly orbital asymmetry = pyrgocephaly
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Turricephaly lambdoid and coronal suture => peaked, tower-like skull also acrocephaly, oxycephaly
Microcephaly all sutures affected, mental defects
Paranasal sinuses Maxillary sinus form after few weeks, into adulthood
4 recesses, maxillary, palatine, zygomatic and alveolar, roots of 1st and 2nd molar can extend into floor drain into ostiomeatal complex in the middle meatus with frontal and ant. ethmoidal air cells (nasolacrimal duct drains into inferior meatus)
Frontal sinus form between 2 and 14 years within frontal bone, can extend into orbital plate, very variable in size middle meatus
Ethmoid air cells as frontal sinus between orbits and nasal cavity, below crista galli ant. cells drain into middle meatus post. cells drain into superior meatus
Sphenoid sinus forms > 3years, can extend into sphenoid or ant. clinoids often incomplete separation of both sides, can be continuous with the (anterior) ethmoid cells, above nasopharynx, medial to cavernous sinus, inferior to pituitary fossa and chiasma opticum, drain into sphenoethmoidal recess
Mastoid air cells pneumatised at 14 Inner ear int. carotid a. antero-inferiorly
jugular bulb inferiorly epitympanic recess above scutum, contains head of malleus and body of incus footplate of stapes in oval window facial nerve posterior wall (after knee) promontory = basal turn of cochlea
Intracranial calcification (normal variants) pineal gland 5% < 10 years, 70% > 70 years, up to 10 mm in size “normal”
5cm post-sup. on a line intersecting the plane of the to clivus at right angles 1 cm below post. clinoids choroid plexus post-sup. to pineal gland habenular calc. choroid plexus in 3rd ventricle ant. to habenular commissure
just ant-sup. to pineal, reverse c-shaped petro-clinoid and interclinoid ligaments, dura, falx and sagittal sinuses Teeth enamel, dentine, pulp & root canal, periodontal membrane, lamina dura CNS Brain does not have lymphatic drainage
Cavum septum pellucidum obliterates 2-3 months post partum Frontal lobe three horizontal gyri, association centres and inhibition
middle: voluntary conjugate eye movements inferior (ant => post): zona orbitalis, tringularis and opercularis, the two latter contain Broca’s area
Basal ganglia Internal capsule
ant. limb transmits cranial nerve fibres from motor cortex post. limb transmits fibres from motor cortex from ant. to post. upper limb, trunk, lower limb separates head of caudate nucleus (ant. limb) and thalamus (post. limb)from lentiform nucleus
Lentiform nucleus globus pallidum (medial) and putamen, separated laterally from claustrum by external capsule Insula separated medially from claustrum by extreme capsule, just deep to Sylvian fissure
Corpus callosum rostrum, genu, body, splenium from ant. to post.
below falx, above septum pellucidum and IIIrd ventricle commissural fibres connecting corresponding parts of the hemispheres
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ant. commissure = frontal fibres form ant. forceps post. commissure = interoccipital fibres form post. forceps
The cranial nerves motor: III, IV, VI and XII autonomic fibres: III, V (secondary), VII, IX, X I. Olfactory tract olfactory bulb above cribriform plate - II. Optic optic canal with ophthalmic artery .-. chiasma - optic tract - lat. geniculate bodies III. Oculomotor between cerebral peduncles - lat. to sella - superolat. wall of cavernous sinus - splits into superior ramus
(mm. levator palpebrae sup. and rectus sup.) and inferior ramus (parasympathetic and other fibres) before entering sup. orbital fissure at risk of compression by post. communicating aneurysm in interpeduncular fossa between post. cerebral a. and sup. cerebellar a. motor: all extraocular muscles except sup. oblique and lat. rectus parasympathetic: m. sphincter pupillae, m. ciliaris Edinger-Westphal, to ciliary ganglion via radix brevis of inf. ramus
IV. Trochlear dorsal surface of midbrain - ambient cistern - tentorium - sella - wall of cavernous sinus - sup. orbital fissure motor: sup. oblique m., reading muscle, int. rotates, adducts and depresses gaze
V. Trigeminal ant.-lat. part of pons - cerebello pontine angle - major part of trigeminal root (sensory) runs as pars compacta to petrosal ridge, becomes looser pars plexiformis before becoming trigeminal (semilunar) ganglion Gasseri (in Meckel’s cave) over tip of pyramid and dividing into three branches. minor part (motor) follows sensory root anteriorly and inferiorly, passes under trigeminal ganglion to join mandibular branch a. ophthalmic branch supplies orbit, cornea, nose, dura, straight and cavernous sinus lat. wall of cavernous sinus - splits into frontal, lacrimal and nasociliary branches - sup. orbital fissure b. maxillary branch supplies face between mouth and ext. canthus, nasopharynx, gums and teeth of maxilla, palate, dura mater of middle cranial fossa lat. wall of cavernous sinus - foramen rotundum - pterygopalatine fossa - inf. orbital fissure - infraorbital foramen c. mandibular branch supplies skin, mucus membranes and teeth of mandible, muscles as below joined by motor root - foramen ovale - infratemporal fossa - - n. alveolaris inf. - for. mentale - n. mentalis - n. lingualis, receives fibres from n. intermedius/chorda tympani via CN VII - n. auriculotemporalis, receives secretory fibres to parotid from CN IX sensory: face, cornea and conjunctiva, mouth and nose, meninges ant. 2/3 of tongue motor: (mandibular branch only) mm. masseter, temporalis, medial and lat. pterygoids, mylohyoid, ant. belly of digastric, tensor tympani and tensor veli palatini
VI. Abducens ant. junction of pons and medulla - prepontine cistern - clivus - tip of petrous bone - through cavernous sinus - sup. orbital fissure motor: lat. rectus
VII. Facialis lat. junction of pons and medulla - cerebello-pontine angle - int. acoustic meatus - facial canal - ganglion geniculi - chorda tympani - ramus to m. stapedius - foramen stylomastoideum - - rr. temporofrontales two - rr. zygomatici zulus - rr. buccales buggered - r. marginalis mandibulae my - r. colli (platysma cat n. intermedius (= lies between VII and VIII): afferent sensory fibres, efferent autonomic fibres, splits in facial canal into 1. n. petrosus major to lacrimal gland and nose 2. chorda tympani to tongue via lingual n. (V.c.) and submandibular ganglion autonomic: submandibular and sublingual glands, lacrimal glands } chorda sensory: ant. 2/3 of tongue } tympani motor: facial muscles, m. stapedius
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VIII. vestibulo-cochlearis post.-lat. junction of pons and medulla - int. acoustic meatus cochlear part more sensitive to damage
IX. Glossopharyngeal
medulla oblongata, post. to olive - anterior part of jugular for. (-branches to carotid plexus) - mm. stylopharyngeus + styloglossus - tongue autonomic: minor petrosal nerve to parotid, fibres to carotid plexus sensory: posterior third of tongue and pharynx middle ear and Eustachian tube motor: m. stylopharyngeus, upper pharyngeal constrictors
X. vagus medulla oblongata, post. to olive - posterior part of jugular foramen - post. to int. jugular v. in carotid
sheath - behind main bronchi and pulmonary aa. - post. pulmonary plexus - ant. and post. vagal trunks along oesophagus autonomic: secretory fibres to respiratory and GI-tract inhibitory fibres to heart sensory: ear, respiratory and GI-tract motor: somatomotor: palate, pharynx, larynx (superior [cricothyoroideus m.] and recurrent laryngeal n.) visceromotor: GI-tract, bronchioles
XI. accessory rootlets from medulla oblongata and cervical cord - ascends through foramen magnum - descends through
posterior part of jugular foramen motor: mm trapezius and sternomastoideus fibres via vagus to striated visceral muscles in larynx, pharynx and oesophagus
XII. hypoglossus medulla oblongata, rootlets post. to olive- ascends through foramen magnum - descends through
hypoglossal canal - follows internal carotid to hyoid bone - tongue motor only: tongue, strap muscles (with fibres from C1-3 via ansa cervicalis profunda)
Optic tract lateral geniculate bodies (=> reflexes) and superior colliculi Acoustic tract medial geniculate bodies and inferior colliculi
Inferior surface of the brain Telencephalon ant. perforating substance behind origin of optic tract, lat. to chiasma Diencephalon tuber cinereum (pituitary infundibulum) and corpora mamillaria behind chiasma Mesencephalon post. perforating substance between cerebral peduncles with origin of CN III Metencephalon pons, separated from middle cerebellar peduncles by origin of CN V (CN IV wraps around sup.
part of pons from dorsally), CN VI from inf. surface Medulla oblong. origin of CN VII and VIII at junction with pons, CN IX, X XI lat. surface, CN XII rostral surface
ant. to olives, decussatio of pyramidal tract Cerebellum behind 4th ventricle, below tentorium, between sigmoid sinuses
grey cortex, deep white matter three pairs of peduncles to 1. midbrain }
2. pons } brainstem 3. medulla oblongata }
Limbic system cingulate gyrus, splenial gyrus, dentate gyrus, hippocampus, fornix, mamillary bodies Midbrain - cerebral peduncles, crura cerebri connecting int. capsule with pons
ant. part = efferent fibres } separated by post. part = tegmentum, afferent fibres } substantia nigra - post. surface = quadrigeminal plate sup. colliculi => lat. geniculate bodies of optic tract inf. colliculi => med. geniculate bodies of auditory tract - sup. cerebellar peduncles, roof of IV ventricle
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Medulla oblongata - ant. part: pyramidal tract with (ventral) median fissure which is obliterated by the decussation - inf. cerebellar peduncles - forms floor of IV ventricle - olives at upper edge
Circle of Willis complete with all branches in only 40% Internal carotid petrosal part branches to eardrum, pterygoid plate, wall of cavernous sinus, pituitary and dura of ant. cranial fossa intracranial part 1. O phthalmic a. orbital canal, crosses nerve from lat. to medial
2. P ost. communicating a. 3. A nt. choroidal a. choroid plexus, ⇔ post. choroidal a. 4. S triate a. lentiform nucleus 5. A nt. cerebral r ecurrent a. of Heubner a nt. communicating a. f rontopolar a. ca llosomarginal a. per icallosal a. c entral a. 6. M iddle cerebral a., largest branch lenticulostriate aa. basal ganglia and int. capsule cortical rr. frontal/parietal/sup. temporal/angular
Vertebral a. 1. meningeal branch post. fossa 2. ant. spinal a. 3. medullar branches 4. PICA inferior cerebellum
Basilar a. 1. pontine branches
2. labyrinthine branches 3. AICA anterolat. cerebellum 4. sup. cerebellar a. superior cerebellum 5. post. cerebral a branches to cerebral peduncles, post. thalamus, med. geniculate bodies and quadrigeminal plate thalamostriate a. thalamus and lentiform nucleus post. choroidal a. choroid plexus cortical branches inf. temporal lobe, occipital lobe
Variants:
hypoplastic ant. communicating a. 3% unilateral supply to ant. comm. a. 2% hypoplastic post. communicating a. 22% fetal post. comm. a. (from middle cerebral) 15%
Cerebral venous system Superior sagittal sinus runs a-p over convexity of brain (which it drains) to sinus confluence
= Torcular Herophili turns to the right to become right transverse sinus => right int. jugular vein usually larger
Inferior sagittal sinus runs a-p in lower edge of falx, joins great cerebral vein of Galen to become straight sinus which usually turns left to become left transverse sinus
Sigmoid sinus extension of transverse sinus after taking up sup. petrosal sinus joins with inf. petrosal sinus in jugular foramen to become the internal jugular vein
Cavernous sinus lies lateral to pituitary and sphenoid bone, inferior to optic tract, extends from sup. orbital fissure to foramen lacerum receives ophthalmic and superf. middle cerebral veins and sphenoid sinus drains via sup. and inf. petrosal sinus into transverse and sigmoid sinus respectively
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both sides connected via intercavernous sinuses around pituitary contains: internal carotid a., CN III, IV, Va+b, VI
Internal cerebral veins formed by 1. septal vein from septum pellucidum 2. choroidal vein from lat. ventricle 3. thalamostriate vein unite to form the great vein of Galen
Basal vein of Rosenthal formed by 1. anterior cerebral vein 2. deep middle cerebral veins from insula 3. striate veins from basal ganglia drain into the great vein of Galen
Superficial cerebral veins 1. superficial (middle) cerebral v. drains lat. surface of brain - Sylvian fissure - lat. sulcus - sphenoid sinus - sinus cavernosus 2. Vein of Labbe anastomoses superficial cerebral v. with transverse sinus in 60% 3. Sup. anastomotic vein of Trollard anastomoses superficial cerebral v. with sup. sagittal sinus in 30 %
Ventricular system 150 ml CSF, 125 ml within cranial cisterns and ventricles, 25 ml in spinal canal, produced in choroid plexus at 25 ml/hr,
absorbed by arachnoid villi penetrating into sinuses, esp. sup. sagittal sinus Choroid plexus - of lateral and third ventricle: continuous from temporal horn through body into third ventricle
ant. choroidal artery from int. carotid a. through temporal horn post. choroidal arteries from post. cerebral a. through body and temporal horn - of fourth ventricle invaginates its roof branch from inf. cerebellar artery
Lateral ventricles open into 3rd ventricles through interventricular foramen of Monroe frontal (anterior) horn floor and lat. wall: caudate nucleus, thalamus medial wall: septum pellucidum roof: corpus callosum no choroid plexus temporal (inferior) horn floor: hippocampus lat. wall: tapetum roof: caudate and amygdaloid nucleus occipital horn very variable in extension, no choroid plexus lies mainly within grey matter of occipital lobe lat. wall: tapetum and optic radiation
Third ventricle flat structure between thalami, contains interthalamic adhesion in 60% (massa intermedia) = non-neuronal connection ant. wall (lamina terminalis): above optic chiasma with supraoptic recess floor: hypothalamus and subthalamic groove infundibular recess into pituitary stalk pineal recess into pineal stalk, suprapineal recess above roof: column (anterior 1/3) and body of fornix
Aqueduct 1.5 cm long, 1.5mm wide anterior to quadrigeminal plate (tectum), behind cerebral peduncles nuclei of CN III, IV and V form periaqueductal grey matter
Fourth ventricle floor (rhomboid fossa): pons / medulla oblongata roof: cerebellar peduncles with sup. and inf. velum Foramen Magendie: post. mid-line opening into cisterna magna Foramina of Luschka: lat. openings into pontine cistern (at apices of lateral recesses under inf. cerebellar peduncles)
Cisterna magna between cerebellum and medulla => 4th ventricle (for. Magendie) => cervical spine (for. magnum) contains vertebral artery and PICA
(Pre-) pontine cistern between pons and clivus => 4th ventricle (foramina of Luschka) => to cisterna magna laterally => interpeduncular cistern above contains basilar artery with pontine and labyrinthine branches
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Interpeduncular cistern between cerebral peduncles and dorsum sellae => suprasellar cistern ant. => ambient cistern post. => pontine cistern below contains post. choroidal a.
Ambient cistern joins interpeduncular with quadrigeminal cistern around midbrain contains post. cerebral and great vein, CN III
Suprasellar cistern above and lat. to pituitary fossa, ant-inf. to III ventricle => interpeduncular cistern post. => Sylvian cistern lat. contains chiasma and ant. part of circle of Willis
Quadrigeminal plate cistern between quadrigeminal plate and tentorium a.p. between splenium of corpus callosum and vermis contains venous confluence (basal and great vein and inf. sagittal sinus)
Pineal gland post. to 3rd ventricle and habenular commissure
calcifies commonly from early 20’s, up to 10 mm on lat.film midline “shift” < 2-3 mm normal
TMJ’s condylar process/head of mandible articulates with mandibular fossa of temporal bone, slips anteriorly
over articular tubercle on opening, covered by fibrocartilage cartilaginous disk divides joint into sup. and inf. part, fixed to condylar process, moves forward with opening of mouth lat. pterygoid m. attaches to disk plain film taken with 30° caudal angulation
Salivary glands Parotid gland lies superficial to masseter m. with isthmus around mandible
ant. relations: mandible, masseter post. relations: mastoid process and sternomastoid m. med. relations: styloid process, pharyngeal mm. 5 cm duct running superf. to masseter m. to pierce buccinator m., os opposite upper 2nd molar ext. carotid a. divides into two terminal branches within post. part at level of isthmus facial nerve runs through deep part superficial to facial a. & v.
Submandibular gl. wrapped around mylohyoid m. from behind, medial to angle and post. body of mandible
5 cm duct comes off deep part, goes over (cranial) to lingual n., opens onto sublingual papilla Sublingual gland multiple ductless opening directly into floor of mouth
Neck
Branchial arches each segment usually supplied by one cranial nerve and one aortic arch
1st branch mandible and face, malleus and incus, muscles of mastication and ant. belly digastricus, mylohyoid, tensor tympani & veli palatini CN V (motor: mandibular branch), maxillary artery ant. 2/3 of tongue 2nd branch styloid process and stylohyoid ligament, stapes, lesser horn and sup. body of hyoid CN VII, connection to V via chorda tympani, arteries to stapes and hyoid 3rd branch stylopharyngeus muscle CN IX, internal carotid artery post. 1/3 of tongue 4th branch superior laryngeal cartilages incl. epiglottis CN X, superior laryngeal nerves 5th branch obliterates 6th branch inferior laryngeal cartilages CN X, recurrent laryngeal nerves
Thyroglossal tract ant to body of hyoid
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Vasculature External carotid
Bifurcation at C4, initially medial to int. carotid, enters parotid 1. sup. thyroid a. (inf. thyroid from thyrocervical trunk / subclavian a.) 2. lingual a. => 3. ascending pharyngeal a. => larynx, meningeal vessels through foramen lacerum 4. facial a. --- ophthalmic a. => face, submandibular gland, soft palate, tonsils 5. sternomastoid branches 6. occipital a. => meningeal vessels through jugular foramen 7. post. auricular a. => pinna, parotid, scalp ================================================== parotid 8. superf. temporal a. --- ophthalmic a. => pinna, parotid, scalp, TMJ 9. maxillary a. --- middle meningeal a. common origin of lingual and facial a. in 20%
Internal carotid lies initially posterior and lateral to external carotid medial to int. jugular vein with vagus nerve post. between them sympathetic trunk post., outside carotid sheath
Vertebral a. through transverse ffor. of upper 6 cervical vertebrae with vertebral vv. (C5 and above in 5%)
cervical branches and ant. spinal a. to cord right brachiocephalic vein receives inf. thyroid vein and right lymphatic trunk SVC formed at T3 Cervical fascia Investing fascia from mandible/zygoma/mastoid to manubrium/clavicle/acromion, includes hyoid and spinous processes Pre-tracheal fasc. below larynx
around thyroid, trachea and oesophagus, fuses with carotid sheath Prevertebral fasc. from sphenoid to T3
encloses spine and pre-vertebral muscles, phrenic nn., sympathetic trunk and brachial plexus Larynx suspended from hyoid by thyrohyoid membrane and ligaments
3 unpaired cartilages cricoid, thyroid and epiglottis 3 paired cartilages arytenoids, corniculates (above), cuneiformes (lat. in aryepiglottic folds) cricoid, thyroid and arytenoids are hyaline cartilages 3 levels vestibule =========================== false (vestibular) cords laryngeal ventricle (± saccule anteriorly) =========================== vocal cords, glottis infraglottic larynx cross-section triangular at level of false cords, elliptical at level of glottis, D-shaped below
Recurrent laryngeal nerves come off vagus nerve, hook around right subclavian a. at T2/3 and aortic arch at T4/5 run in groove between trachea and oesophagus => local branches, medial to thyroid
Thyroid thyroid cartilage to 6th tracheal ring (C5-T1, ~ 4cm), isthmus at C6
pyramidal lobe in 40%, arteria thyroidea ima from aortic arch in 10% thoracic duct behind left lobe lateral to superior and recurrent laryngeal nn.
Aa. sup. thyroid artery --- ext. carotid (1st branch) } inf. thyroid artery --- thyrocervical trunk } -- arterial plexus a. thyroidea ima (10%) --- brachiocephalic / aortic arch }
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Vv. sup. and middle thyroid vv --- int. jugular inf. thyroid v. --- left brachiocephalic v.
Parathyroid glands
within pretracheal fascia behind . thyroid superior glands constant at C6, inferior glands can lie deep within thorax supplied by inf. thyroid a.
Stellate ganglion fusion of inferior cervical and 1st thoracic ganglion above first rib, ant. to transverse processes of C7, behind vertebral a.
Thorax Ribs 7 true, 3 false (do not reach sternum), 2 floating
1 ½ facets for their own rib and the one below (except T11 + 12) cervical ribs occur < 1%, 50% bilateral, twice as common in women Vasculature Variants of the aortic arch - both common carotids of innominate a. 27% - left vertebral a. from arch 4% - right vertebral a. from right subclavian a. 90% - anomalous right subclavian (a. lusoria) 1-2%, off descending aorta, pre-/postoesophageal, pretracheal aortic diameter root 4.5cm (angio) ascending 4cm
arch 3.5 cm descending 3cm abdominal 2cm bifurcation 1.5 cm
Aortic nipple left sup. intercostal vein viewed tangentially in front of aortic knuckle
Left SVC connection between left sup. intercostal vein and oblique cardiac vein Azygos system azygos vein L2, from right ascending lumbar and right subcostal vein or as branch of IVC
ascends to right of aorta and thoracic duct through aortic hiatus (median arcuate lig.), medial to right lung and pleura, arches forward over right hilum at T4 and feeds into SVC
receives all but 1st intercostal vein, right bronchial, oesophageal, mediastinal and pericardial veins hemiazygos v. L2, from local veins as azygos ± renal vein, passes behind aorta at T7 (variable) to feed into azygos access. azygos v. 4th-8th post. intercostal veins, runs caudally to pass behind aorta above hemiazygos 1st right and 1st-3rd left intercostal veins drain directly into brachiocephalic veins Thoracic duct contains valves, ascends to the left of azygos v., crosses to the left at T5 to lie posterior to oesophagus and
aortic arch feeds into left brachiocephalic vein at C7
The Heart Eustachian valve directs venous blood returning into right atrium to foramen ovale
Projection of heart valves within cardiac shadow p.a. film aortic midline at junction of 3rd costal cartilage with sternum
mitral (patient’s) left of midline at junction of 4th costal cartilage with sternum (below and to the left of aortic valve) pulmonary above and to the (patient’s) left of aortic valve, highest and most anterior valve tricuspid anywhere on a line from the junction of the right 6th costal cartilage with sternum to the mitral valve (i.e. low and to the right)
lateral on a line from the carina to the anterior cardiophrenic angle aortic above, projecting under aortic root mitral below, posterior to aortic valve
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coronary arteries LCA dominant in 15-20%, balanced 20-30%, RCA dominant in 50-60%
left c. a. 1. left anterior descending a. to septum and apex
septal and two diagonal branches, occ. branch to right ventricle 2. left circumflex artery to posterior wall, anastomoses with post. descending a. obtuse marginal a. to lateral wall, atrial branches
right c. a. branches to pulmonary outflow tract, branch to SA-node marginal branches to right ventricle branch to AV-node posterior descending a.
cardiac veins draining into the coronary sinus are from the left great cardiac vein (LAD)
left posterior ventricular v. (obtuse marginal a.) left oblique atrial v., oblique vein of Marshall
from the right small cardiac v. (anterolateral wall) middle cardiac vein (posterior descending a.)
anterior cardiac vv. from the anterosuperior wall and pulmonary outflow tract directly into the right atrium Lungs Trachea starts at C6, carinal angle 50-65°
left main bronchus = hyp(o)arterial bronchus (under artery) 5 cm long right main bronchus = ep(i)arterial bronchus (behind artery) 2.5 cm long
segmental bronchi divide into 6-20 respiratory bronchioles => terminal bronchioles (no cartilage within wall) => alveoli
acinus resp. bronchiole + alveolar duct + alveoli lobule 3-5 acini separated by septa Pores of Kohn air flow between alveoli Channels of Lambert air flow between alveoli and term. bronchioles
interstitial lines interlobular septa Kerley B deep septa Kerley A
Hila project over 7-8th post. rib Hilar point intersection of upper lobe vein with descending inferior lobe artery Hilar angle 120° Oblique fissure from T2 to 6th rib parasternally, left runs steeper course (60°) than right (50°) Horizontal fissure intersects interlobar a. 1 cm below right hilar point Accessory fissures inferior acc. fissure 8 %, commonest, separates mediobasal segment of right lower lobe
superior acc. fissure 5%, separates apical segment of right lower lobe azygos fissure < 1%, azygos vein pushed into upper lobe => contains four layers of pleura
Paratracheal stripe right < 3mm, left not present due to aortic arch Parasternal stripe < 7.5 mm, wavy Retrosternal stripe < 3 mm, ant. edge of lungs, straight Pleural reflections 6th - 8th - 10th - 12th rib parasternal - MCL - MAxL - paravertebral Lung border 6th - 8th - 10th MCL - MAxL - MScL
[mid-clavicular / -axillary / -scapular line] pulmonary veins run antero-inferior to arteries diameter of pulmonary arteries < 1.5 x the corresponding bronchi pulmonary vessels should be < 3mm in diameter in 1st ICS lower lobe a. should be less than 16 mm in diameter (14 mm in women) on a rotated CXR the lung away from the film appears more radiolucent
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The Breast acini => lobules => lobular duct => 15-20 lobes => lactiferous ducts => nipple parenchyma enclosed in superf. fascia anteriorly and deep fascia posteriorly separated from pectoralis major m. by pectoralis fascia acini increase in number during pregnancy and breast feeding involute after lactation resulting in reduced glandularity than
pre-pregnancy glandular breast more difficult to assess on mammography as increased radiodensity Cooper’s ligaments
septa running through breast from pectoralis fascia to skin
blood supply 1. int. thoracic a. (subclavian a.) 2. lat. thoracic a. (axillary a.) 3. branches of intercostal aa. venous drainage analogous
lymph drainage 1. axillary nodes 2. internal thoracic nodes 3. cross-over to contralateral side (!)
Abdomen Oesophagus C6 - diaphragm at T10
four narrow segments 1. behind cricoid 2. behind aortic knuckle 3. behind left main bronchus 4. piercing the diaphragm striated muscle in upper 2/3 maximal diameter smaller than that of pylorus
Diaphragm trigonum sternocostale, Larrey internal thoracic vessels => superior epigastric vessels Foramen venae cavae Right central tendon, T8: IVC, Right phrenic nerve oesoph. hiatus fibres of median arcuate ligament, ant. to aortic hiatus, T10 oesophagus, vagal trunks, arterial and venous anastomoses median arcuate ligament aortic hiatus, T12: aorta, thoracic duct, azygos vein medial arcuate ligaments psoas arcade, L2: psoas muscles, sympathetic trunk lateral arcuate ligaments L1: quadratus lumborum = trigonum lumbocostale Bochdalek
Phrenic nerve C3/4/5 (keep the diaphragm alive) right: ant. to scalenus ant. m./behind right subclavian vein - lat. to SVC/right atrium/IVC left: ant. to scalenus ant. m./behind thoracic duct and origin of right brachiocephalic vein - lateral to aortic arch/left atrium/left ventricle
Stomach Fundus enhances with iv-contrast Small bowel Circumferential folds contain mucous membrane only, do not disappear on dilatation Mesentery extends from L2-vertebra to right SI-joint
Duodenum independent peristaltic pacemaker
D1 intraperitoneal D2 longitudinal ridge, begin of circumferential folds accessory papilla in 10% on anterior wall of D2, proximal to major papilla
Jejunum larger diameter } thicker wall } than ileum more prominent valvulae conniventes } complex arterial arcades with extensive anastomoses
Ileum arterial arcades reduced to max. 3
cobblestoning due to hyperplastic lymph follicles normal between 3-16 years Peyer’s plaques = lymph follicles in ileum
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Meckel’s diverticulum 1 - 1.2 m proximal to ileocaecal valve, contains gastric mucosa or pancreatic tissue => accumulate pertechnetate
Large bowel Ascending and descending colon usually retroperitoneal
= neither have a mesocolon in 50 % = both have a mesocolon in 15 %
supplying arteries = endarteries Marginal artery of Drummond
artery running along watershed area of splenic flexure, anastomoses SMA and IMA Anal canal
|| || ====== sup. rectal a. + v. int. iliac lymph nodes <= || HINDGUT || || || -------------------------- || ~~~~~~~ linea dentata ~~~~~~~ || ====== middle rectal a. || === external (voluntary) sphincter === || inguinal lymph nodes <= || || || ANAL PIT || ====== inf. rectal a. + v. Skin line _____|| ||_____
Pre-sacral space max. 1.5 cm at S4 on lat. Ba-enema Rectal ears herniation of recto-sigmoid into inguinal hernia
Liver largest solid organ
hepatic vv. join IVC at T12 Falciform ligament
anatomical division of the upper surface of the liver, separates lateral segments of left lobe from caudate and quadrate lobe. Ligamentum teres and venosum follow the same course on the under surface of the liver.
Ligamentum teres obliterated umbilical vein which transports blood from the placenta to the fetus runs in free lower edge of falciform ligament from the anterior inferior edge of the liver to the porta
Ligamentum venosum continues the course of the lig. teres from the porta posteriorly to the IVC, remainder of the ductus venosus Arantii which shunts blood from the portal vein to the left hepatic vein or IVC (bypassing the liver) in early and middle pregnancy
Liver segments 1 caudate lobe } 2 lateral superior segment } left 3 lateral inferior segment } lobe 4 quadrate lobe } ======================= middle hepatic vein 5 anterior inferior segment } 6 posterior inferior segment } right 7 posterior superior segment } lobe 8 anterior superior segment }
Caudate lobe between IVC and ligamentum venosum possesses own venous drainage direct to SVC => hypertrophies in Budd-Chiari syndrome as all others blocked. Portal venous and arterial supply from both sides
Riedel’s lobe caudal extension of segment 5, not a true lobe (B. Riedel, 1846-1916, Professor of surgery in Jena, Germany)
Omentum minus, lesser net
ant. to post.: CBD - hepatic a. - portal vein right hepatic a. post. to common duct in > 90%
Bursa omentalis, lesser sac separated from peritoneal cavity (greater sac) ant: omentum minus inf.: mesocolon transversum left: gastrolienal ligament right: continuous through foramen epiploicum Winslowi
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Portal system and umbilical vessels portal vein formed behind neck of pancreas by joining of splenic vein (which has already received IMV) and SMV umbilical vein one vein, umbilicus to portal vein in free lower edge of falciform lig., obliterates to lig. teres ductus venosus portal vein to left hepatic vein or IVC (bypassing the liver), obliterates to lig. venosum umbilical arteries two arteries, from the two internal iliac arteries to the placenta Pancreas rotation of duodenal ectoderm leaves ventral bud to the right, dorsal bud to the left ventral bud migrates dorsally to lie inferior to dorsal bud and become uncinate process and lower part of head with distal part of major duct Spleen splenic aa. + vv. divide into 4-5 branches before entering the hilum Lienorenal lig. “mesosplenium” Gastrolienal lig.
Splenunculi occur in 10%, usually < 1cm Kidneys tilted 45° backwards
arteries divide into lobar branches before entering kidney, accessory arteries enter kidney direct (extrahilar), no anastomoses at segmental level renal aa. post. to pelvis, vv. ant to pelvis, double veins in 10%
Adrenal glands at birth 1/3 size of kidneys, involute to 50% within 3/12 Blood supply: 1. inferior phrenic a.
2. middle adrenal a., origin at T12/L1 3. renal a.
Suprarenal vein drains to IVC (right) and renal vein (left) CT: up to 4cm long, limbs < 10 mm thick
right V-shaped, left Y-shaped Lymphatic drainage Stomach upper abdominal nodes Small bowel mesenteric nodes Bladder external iliac nodes Prostate int./ext. iliac and sacral nodes Ovaries lateral- and preaortic Coeliac ganglion, plexus solaris
lat. to aorta, between coeliac axis and renal aa. Pelvis Pectineal line pubic tubercle - ilio-pubic eminence Spaces of the perineum:
Bladder ===================== levator ani Prostate ===================== uro-genital diaphragm superficial perineal space ---------------------------------- superficial perineal fascia
Ischio-rectal fossa inf. to levator ani, lat. to rectum, medial to int. obturator m.
Vasculature Internal iliac a. forms at L5/S1 in front of SI-joint Anterior division Obturator a. through obturator foramen to thigh
Umbilical a Superior vesical a. bladder Inferior vesical a. bladder, seminal vesicles, prostate / vaginal a. Middle rectal a.
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Uterine a. lig. latum to cervix, uterus, Fallopian tubes and ovaries <=> ovarian aa. Inferior glutaeal a. through greater sciatic foramen to buttock and thigh Internal pudendal a. greater sciatic foramen - hooks around ischial spine - lesser sciatic foramen => external genitals => inferior rectal a.
Posterior division Iliolumbar a. iliopsoas m., cauda equina Lateral sacral a. through ant. and post. sacral ffor., sacral canal and lower back Superior glutaeal a. through greater sciatic foramen to pelvic wall and thigh
External iliac a, inferior epigastric a. anastomoses with sup. epigastric a. from int. thoracic a. abdominal wall, scrotum/vulva deep circumfl iliac a. abdominal wall
Bladder blood from sup. and inf. vesical (sive vaginal) a.
lymph drainage: mainly external iliac nodes Prostate underneath bladder, on top of uro-genital diaphragm, post. to lower edge of symphysis
prostatic vv. drain to internal iliac v. and int. and ext. prevertebral plexus => metastases lymph drainage: mainly int. iliac nodes ± ext. iliac nodes
Penis root in superficial peroneal space bulb beneath UG-diaphragm, crura from ischio-pubic rami suspensory ligament from anterior edge of symphysis fundiform ligament loops around penis with two origins from linea alba supplied by int. pudendal a.
pre-vesical space of Retzius Donovillier’s fascia separates prostate from rectum, relative barrier for local spread of malignancies Upper limb Vasculature nutrient vessels to the bone “go to the elbow and flee the knee”
Subclavian a middle part runs behind scalenus ant. together with brachial plexus
(s-cl. v. ant. to scalenus ant. m. and behind sternomastoid) aberrant right s-cl.a. usually passes behind oesophagus (dysphagia lusoria) branches: 1. vertebral a. 2. thyrocervical trunk => suprascapular a. and cervical branches, inf. thyroid a. 3. internal thoracic a.
Axillary a. from lat. border 1st rib to inf. border of teres major m. through brachial plexus to lie between radial nerve post., median n. supero med., ulnar nerve inf. 1. sup. thoracic a. 2. acromiothoracic trunk 3. subscapularis a 4. ant. & post. circumflex humeri aa. 5. lat. thoracic a.
Brachial a. from inf. border of teres major to below elbow => bifurcation ant to radial head 1. pofunda brachii => in radial groove 2. nutrient a. of humerus 3. muscular branches 4. branches to elbow
Ulnar a. larger, deeper branch, gives off common interosseus a. becomes superficial at wrist, over flexor retinaculum => superficial palmar arch
Radial a. becomes lat. at wrist joint, branch to superf. palmar arch, runs at bottom of anatomical snuffbox to the back of the hand => deep palmar arch
Veins median v. from palmar surface
cephalic and basilic vv. from dorsum of hand, cephalic v. runs laterally, has to pierce clavipectoral fascia at the shoulder => contrast stasis
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Shoulder glenoid covers 1/3 of humeral head
capsule inserts behind labrum and at anatomical neck long biceps tendon runs intra-articular to insert into labrum glenoidale acromio-humeral distance > 7mm lymph drainage: axillary and deep cervical nodes
Rotator cuff supraspinatus, infraspinatus, subscapularis and teres minor stabilise the joint from all sides supraspinatus tendon runs under acromion and separates sub-acromial bursa from joint space sub-acromial bursa - subdeltoid bursa = largest bursa in the body, does not communicate with joint space unless supraspinatus tendon is gone ubscapular bursa communicates with joint space
Elbow 3 joints, one synovial space carrying angle: male 160° forearm flexors originate from medial epicondyle
Wrist two separate joint spaces, radio-carpal and intercarpal joint
disc in ulno-triquetral articulation Flexor retinaculum superficial palmaris longus m.
ulnar n. & a. flexor carpi ulnaris via pisiform (= sesamoid) to hook of hamate and base MTC V
lateral radial a. & n. flexor carpi radialis in carpal canal to base of MTC II + III deep deep and superf. finger flexors, long thumb flexor Carpal angle angle between the two tangents of the lower carpal row, 125° - 140°
Accessory carpal bones
os centrale overlying junction of capitate, trapezoid and scaphoid os radiale ext. distal to radial styloid
Metacarpal index mean ratio of metacarpal length to width (of MC II-V, width at mid-shaft) normal <8, if >8.4 => arachnodactyly
Lower limb Vasculature Common femoral a.
continuation of ext. iliac a. after passing through lacuna vasorum of inguinal ligament 1. superficial circumflex iliac a. 2. superficial epigastric a. 3. external pudendal a. 4. profunda femoris a. med. + lat. circumflex aa., collaterals to knee and glutaeal region perforating aa. to muscles
Superf. femoral a. deep to sartorius m. between adductor and extensor group => adductor canal descending genicular branch to genicular anastomosis adductor hiatus between femur and femoral v., deep to tibial nerve
Polpiteal a. four genicular branches crosses politeal fossa from medial to lateral deep to vein (deep to tibial n.) tri-furcation behind prox. tibio-peroneal joint 1. ant. tibial a. pierces interosseus membrane med => lat to lie on ant. surface of it and lat. to tibia, becomes dorsalis pedis a. between malleoli most lateral of the three vessels in ap-projection
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2. post. tibial a. / tibioperoneal trunk continues caudally on post. surface of interosseus membrane becomes tibialis post. a. passing behind lateral malleolus main supply of the foot as the medial and lat. plantar aa. most medial of the three vessels in ap-projection 3. peroneal a. projects between tibial vessels on ap-view, ends at calcaneus
Veins 1. paired deep veins system follow arteries
2. long saphenous v., ant. to medial malleolus 3. short saphenous v., post. to lat. malleolus
Hip Y-line over sup. borders of femoral head epiphyses
acetabular angle 28° ±15 < 3 months between Y-line and acetabulum 22° ±10 < 12 months
angle of NOF 160° in infants 125° in adults anteversion of NOF 30-50° < 1 year 10° in adults => int. rotation educes foreshortening of neck
Shenton’s line: lower edge of n.o.f. should be in continuity with lower edge of upper pubic ramus (> 1 year) Thigh 3 geographical muscle groups 1. anterolateral, supplied by femoral nerve
quadriceps femoris sartorius
2. posteromedial, supplied by obturator nerve adductor longus, brevis and magnus gracilis pectineus
3. posterior, “hamstrings”, supplied by sciatic nerve semimembranosus semitendinosus (superficial to semimembranosus) biceps femoris
Sartorius m. from ant. sup. iliac spine to medial tibial plateau passes post. to knee joint => flexor of knee and hip, ext. rotator of thigh, int. rotator of leg = tailor’s muscle
Femoral A. & V. deep to sartorius Long saphenous v. between gracilis and sartorius Knee physiological valgus of 80° in males, 76° in females
=> medial condyle larger to allow horizontal tibial plateau => patella dislocates laterally
7 bursae gastrocnemius, popliteus, semimembranosus and suprapatellar bursa communicate with the synovial cavity, 3 further bursae around patella these do not communicate
Cruciate ligaments ant. cruciate lies anterolateral to the post. ligament runs from above and lateral to down and medial (= parallel to fibres of external oblique m.) intraarticular but extrasynovial post. tightens on flexion
Menisci fibro-cartilagenous discs, attached to femoral condyles via coronary ligaments ant. edges joined by transverse ligament medial larger, open “C” with ant. and post. attachments to tibial plateau anterior to respective cruciate lateral smaller, near-complete circle with attachments between cruciates
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Pes anserinus (lat. goosefoot) insertion of sartorius, gracilis and semitendinosus into medial tibial plateau Calcaneus Boehler’s angle (intersection of tangentials along cranial surface and subtalar surface) 30-35°
if < 28° => fracture
Foot Sesamoid bones
os peroneum 20% lat. to proximal cuboid, peroneus longus tendon os vesalianum lat. to base of Vth metatarsal os trigonum 8% behind talo-calcanear joint os tibiale externum medial to navicular tuberosity, tibialis post. tendon?
Heel pad thickness males: < 23 mm females: < 21 mm
Anatomical levels (body of vertebra) Neck
C1 C2 C3 C4 carotid bifurcation C5 C6 cricoid cartilage, begin of oesophagus and trachea, thyroid isthmus C7
Chest
T1 T2 sternal notch T3 formation of SVC manubrium T4 aortic arch, azygos => SVC manubrium, angle of Louis T5 carina (+/- 1 on deep in-/exspiration), angle of Louis T6 xiphoid process T7 T8 IVC pierces diaphragm T9 T10 oesophagus pierces diaphragm, g/o-junction T11 gallbladder T12 aorta pierces diaphragm, tail of pancreas
Abdomen
L1 coelic axis, SMA originates <6mm inferiorly, pylorus L2 lower end of Left diaphragmatic crus, renal hilum (vein sup. to artery), begin of hemi-/ azygos vv. L3 lower end of Right diaphragmatic crus, origin of IMA, gonadal aa. L4 aortic bifurcation L5 begin of IVC
Pelvis
S1 S2 S3 begin of rectum S4 S5 femoral heads ischio-rectal fossa, cervix symphysis bladder neck, prostate
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RADIOGRAPHY
Tomography blurring - proportional to swing angle
- due to the geometry more pronounced on the tube side of the fulcrum plane than on the film side - independent of exposure factors (these need to be increased by appr. 10 kV and 5 mAs
no effect on radiographic sharpness linear lower dose than cyclical / helical
10° angle 6.9 mm slice thickness 20° angle 3.4 mm wide-angle: reduced contrast, hence more suitable for high inherent contrast areas i.e. bone, middle ear objects parallel to tube motion give streak/parasite artefacts
cyclical phantom images, particularly for small arcs Orbits and paranasal sinuses pa position markedly lower dose to eyes than ap Surface Landmarks ant. chest sternal notch T 2
angle of Louis T 4 xiphoid process T 6
Positioning always relative to film
LAO - left shoulder to film, patient facing film, pa beam left decubitus - right side elevated
Plain Films Head and neck - Skull O.F. 20 (pa) prone, baseline 90° to film, 20° caudal angulation centred through nasion
70 kV, 30 mAs, focused grid Towne’s view supine, baseline 90° to film, 30° caudal angulation (O.F. 30) centred frontal bone => foramen magnum reversed Towne’s = same projection with O.F. beam (cranial angulation) SMV extended neck, film on vertex parallel to baseline; centred through midpoint between angles of mandible with 5° angulation towards forehead O.M. prone, mouth on film, baseline 45° to film beam 90° to film through lower orbital margin (= p.a. with patient looking up) O.M. 30 prone, mouth on film, baseline 45° to film (patient looks up) 30° caudal angulation through vertex to lower orbital margin IAM seen on not on Towne’s view OF 20 SMV OM
Upper Limb - Hand pa 3rd MCPJ,
lat (= obl) 5th MTPJ, then tube angled with central beam through 3rd MCPJ 45 kV
- Thumb pa MCPJ; retroverted arm, abducted thumb
lat MCPJ; abducted thumb, extended wrist, flexed MCPJ’s - Wrist pa midline distal radio-ulnar joint,
lat radio-ulnar plane perpendicular to film (= hand slightly supinated) 50 kV
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- Scaphoid 1. dv 2. dv; tube angled 25° proximally
3. oblique in 45° pronation 4. lat in 0° - Elbow ap 1inch distal from midline between humeral epicondyles; full extension
lat lat. epicondyle; right angles shoulder and elbow, 0° pronation 55 kV
- Humerus ap midshaft; abducted shoulder 45°, extended elbow
lat midshaft; elbow 90°, hand on hip (= 90° int. rotation) - Shoulder ap proc. coracoideus (possibly slightly medially and caudally to fill picture) incl. upper part of
thorax and lower c-spine ap (trauma) slight dorsal rotation to get glenoid tangentially; collimated on joint mod. axial 1. curved cassette in axilla with cranio-caudal beam or 2. caudo-cranial beam tang chest wall 60-65 kV
Lower Limb - Hip von Rosen’s view int. rotation and 45° abduction
axes of femora should cross in front of promontory in midline frog view flexion and ext. rotation with soles together
? epiphysiolysis
- Knee ap full extension; 2.5 cm below lower pole patella lat. superimpose condyles tunnel kneeling on film or curved cassette skyline flexed 90°, patient holds cassette 60 kV
- Lower leg ap midline knee-ankle lat 1, as for lat. ankle, i.e. int. rotated 2, as for lat. knee
- Ankle ap midline between malleoli; plantar flexion ankle/15° cephalad to open up ankle joint lat mild int. rotation to superimpose (post.) fibula with tibia
- Calcaneus pa full dorsal extension of ankles, shoot through soles lat
- Foot dv cuboid/navicular area lat (oblique) lat. border elevated 15° 50 kV
Spine - c. spine ap centre sternal notch, angle up through cricothyroid to compensate for lordosis
lat. increased FFD, “air-gap” technique centre 2.5 cm behind mandible
Chest 70 kV, 6mAs
pa ap film should be marked scapulae rotated out of lung fields vertebral laminae visualised with diverging beam vertebral endplates seen LAO aortic arch, tracheal bifurcation RAO left atrium and ventricle apical lordotic view apices, interlobar areas, pulmonary segments
High kV technique 110-150 kV - shorter exposure => reduced motion unsharpness - more efficient patient penetration => reduced patient dose
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- more forward scatter reaching the film => higher grid ratio required - reduced radiographic contrast => bones less prominent - increased exposure latitude
Automated multi-beam exposure radiography, AMBER horizontal fan beam scans patient exposure factors fixed: 130 kVp, 20-60 mAs (dependent on patient size) array of twenty detectors behind patient and 20 corresponding step-wedge filters between tube and patient dose for each segment of the beam is modulated via feedback from the detector to the attenuator => much more homogenous exposure with reduced contrast and better penetration of thick structures
Abdomen on arrested inspiration, should include hemidiaphragms and pubic symphysis centred at L4 65-70 kVp, grid!
decubitus named after the side touching the film => left decubitus = right side up detects up to 1 ml of free air dependent diaphragm lies higher within chest and moves less
Autotomography
spine } scapula pa }ribs, breathing oblique sternum } upper c-spine jaw movement
Mammography at present most sensitive method for detection of microcalcification, MTF 20-22 lp/mm, supplemented by7.5 MHz USS skin dose 6-8 mGy, effective dose 0.5 - 1 mSv breast tissue most sensitive to irradiation in late pregnancy and lactation induction of neoplasm by mammography 2 per Mio • Mo-anode and -filter (0.3 mm) for 25 kVp or W-anode and
46Pd-filter for 30 kVp
• fine focal spot (0.1-0.3 mm) => long exposure (>0.5 s) • single sided film/screen, low kVp (25-30 kV) for high contrast • processed at lower temperature with longer cycle • compression vital => immobilisation and dose reduction • cranio-caudal and oblique views at the level of the nipple, including axillary tail Macroradiography
Magnification factor F F DF O D (magnification approx. = 1, if object in contact with film)
- usually 1.5 - 2 times - ultrafine focus required (penumbra directly related), i.e. 0.1-0.3 mm => low tube rating => long exposure times => immobilisation required - screen unsharpness improved as spatial frequencies reduced by magnification - geometric and movement unsharpness worsened - quantum mottle unchanged
Xeroradiography exposure of semi-conducting Se-plate pre-charged at 1600 kV
wide image altitude strong edge enhancement due to increase of electric field around edges non-linear MTF, ideal reproduction of spatial frequencies between 15-50 lp/cm
Pelvimetry Indications: cephalo-pelvic disproportion persistent breech
small stature (of mother), < size 4 shoes post emergency Caesarean non-engaging head prev. difficult labour
Contraindication: labour 1. AP pelvis & erect lateral plain films with air-gap technique 2. CT-scanogram
AP-inlet upper edge of symphysis - promontory 11 cm AP-outlet lower edge of symphysis - lowest fixed part of sacrum 11.5 cm Transverse inlet (maximal lateral diameter) 12.5 cm
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Interspinous distance (ischial spines) 10 cm
Contrast media, CM 1. Intravascular balance of number of molecules : number of iodine atoms toxicity is a function of osmolality and whether agent is ionic or not anaphylactic reactions 6-10 times more common with ionic agents Ionic agents (3:2) Benzene ring with iodine in 2, 4 and 6-position
- toxic until amide groups substituted at position 3 and 5 - if benzene-ring substituted with organic group at 5C => renal excretion, if not => high protein binding and hepatic uptake
differences between agents: - differences in side chains - concentration - methyl-glucamine (meglumine) versus sodium salts: Sodium salts Meglumine salts irritant to vessel wall +++ + cardiotoxic* ++ ++ neurotoxic +++ + anaphylactic reactions x4 more common *for cardiac work mixture with physiological concentration of sodium ideal
osmolality typically 5-7 times osmolality of plasma (1200-200 mosm/kg)
=> vasodilatation, release of histamine, vascular and blood cell injury osmolality is a function of particles in solution (and as ionics dissociate, there are two per molecule), but indirectly related to the molecular weight meglumine diatrizoate (Urografin®)
Side-effects 1. activation of complement
2. release of histamine => anaphylaxis 3. osmotic effect => fluid-shift, alteration of erythrocytes (haemolysis, educed flexibility) sickle cell! 4. toxic effects - vascular vasodilatation, hypotension, tachycardia - cardiac drop in systolic and increase in diastolic pressure, bradycardia, arrhythmias - renal hypotension, hyperosmolar, chemotoxic, precipitation of proteins (myeloma, Waldenström, Tamm-Horsfall = normal protein produced by tubulo-epithelial cells)
Non-ionic agents (3:1) do not dissociate, approx. half the osmolality of ionic agents, in fact less as larger molecules tend to aggregate leading to relative increase in molecular weight, majority of agents for intravascular administration metrizamide first compound, expensive and inconvenient to use as available as a freeze-dried powder only
iohexol (Omnipaque®) Dimeric agents ionic (6:2) Na-/meglumine ioxaglate (Hexabrix®) non-ionic (6:1), extremely low toxicity, hypo-osmolar => saline added
iotrolan (Isovist®), first compound, licensed for myelography 1990 iodixanol (Visipaque®)
heterotopic excretion renal in oral cholecystograms, if biliary obstruction biliary in iv media, if renal failure
intravenous arm pain following injection indicates stasis => basilic vein preferable, more common with sodium salts of high concentration time to left ventricle 10-15 sec.
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2. Oral Barium sulphate
inert within GI-tract, can cause obstruction above tight stricture harmless within lungs, high mortality if intraperitoneal or intravascular powdered suspensions, particle size 0.1 - 3 µm better coating with higher concentrations => higher viscosity less flocculation with smaller particle size => more expensive concentration: 30 - 250 % weight/volume (g/dl)
Gastrografin® HOCM, mixture of meglumine and sodium diatrizoate with 370 mg Iodine/ml hyperosmolar effect within GI-tract => therapeutic for meconium ileus intrapulmonary => pulmonary oedema intraperitoneal => paralytic ileus
CT 1.4% w/v Barium or 2% Gastrografin bowel artefacts if scan time > 5 sec
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RADIOLOGICAL TECHNIQUES
Angiography access: right side easier for right-handed, always scrub both femorals in case of difficulties
Right axilla => ascending aorta Left axilla => descending aorta
Sones-technique: coronary angiogram / left ventricle; cut-down onto brachial artery, single catheter, no sheath
Guide wires 2 wires within coil of third, only one forms tip => flexible can have stiff and floppy end J-tip with 3mm, 7.5mm or 15mm curve coating: polyethylene standard Teflon reduced friction but increased thrombogenicity hydrophilic slippery when wet, good torque
Size catheter: 1 French = 0.3 mm circumference, length in cm guidewire: 1/1000 inch (milli-inch) in diameter, i.e. size 38 = 0.038 in = 0.97 mm size 35 = 0.035 in = 0.89 mm
Angiographic catheters Headhunter standard for selective cerebral angiography, single end-hole Sidewinder / for visceral or difficult selective cerebral angiography Simmons reformable loop, advances on traction, single end-hole Cobra standard visceral catheter, single end-hole Pigtail for large volumes fast, i.e. flush aortography end-hole and multiple side-holes Judkin’s coronaries from femoral approach, different shape for left/right coronary Sone’s coronaries from brachial approach, one shape, femoral use possible Chiba Sheldon sideholes, direct vertebral puncture
clot formation at catheter tip is directly related to catheter size and length and indirectly to the size of the artery Coronary arteriogram
2-9 ml hand injected, very fast frame rate (60 fps), CM should disperse immediately, otherwise catheter might be occluding the artery => immediate withdrawal
Selective cerebral angiography 5F Headhunter ± Sidewinder, sheath makes catheter exchange easier hand injection 8 ml for carotids, 5-6 ml for vertebral arteries projections: carotid O.F. 20 ± cross compression vertebral: reversed Towne’s view lateral lateral lateral obliques
Aortic arch angiogram 5F pigtail 40 ml LOCM 350 pump injected 20-25 ml/s LAO: origin and bifurcation of RIGHT common carotid RAO: origin and bifurcation of LEFT common carotid
Flush aortogram (abdominal) 50 ml LOCM 350 pump injected 12 ml/s
Aorto-femoral arteriogram 5F pigtail or straight catheter with multiple sideholes 120 ml of diluted contrast, LOCM 350 : NaCl = 1:1 pump injection 24ml/3 sec 8ml/s images at 1fps proximally, 2 fps distally
Translumbar aortogram 40 ml of LOCM 320 14 ml/s 10 ml test injection of contrast obligatory a. high puncture, aimed at T12/L1, above / below 12th rib angling medially and cranially for anterior edge
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of vertebral body shows renal arteries, obligatory if aneurysm suspected b. low puncture, aimed at L3, above iliac crest
Mesenteric arteriogram Cobra catheters, iv Buscopan to avoid bowel artefacts for combined procedures IMA should be examined first => bladder filling (!) a. coeliac axis 36 ml LOCM 350 6 ml/s b. SMA 50 ml LOCM 350 8 ml/s c. IMA origin anterolaterally to the left at L3 => LPO best projection 25 ml LOCM 350 3 ml/s or hand injection of 10 ml
Pulmonary angiogram Grollman pulmonary pigtail catheter half-way between pulmonary valve and bifurcation filling enhanced by balloon-occlusion 40 ml LOCM 350 25 ml/s a.p. film most important, ± ant. oblique of the side of interest
Renal arteriogram Cobra / renal double curve catheter 10-15 ml of LOCM 300 via hand injection, alternatively flush aortogram
Digitised intravenous arteriography, DIVA 50 ml LOCM 240 - 270 pump injected via large (16G) needle in antecubital fossa over 2 sec
Venography Adrenal venography
if possible simultaneous hormone sampling Right side more difficult as vein feeds into vena cava 2 ml of CM Left side drains into renal vein 8 ml of CM slow injection to avoid rupture
Percutaneous splenoportography
posterior axillary line puncture angling anterior and cephalad pulp pressure < 11mm Hg gelfoam for haemostasis
Interosseus venography
Lymphography Vessels visualised by injection of methylene-blue s.c., taken up within 30 min, cannulation with 30G needle a. Lipiodol has the advantage of showing lymph nodes as well as vessels, lymphangiogram persists up to 3 days, lymph
nodes are demonstrated up to one year => control for cytotoxic therapy 7 ml per leg, 4 ml per arm, if patient with respiratory compromise only right leg injected with 10 ml as more cross over from right to left side, if other side needs demonstrating as well > 7 days injected over 45 min or until L3 level reached
b. LOCM 240, 10 ml demonstration of vessels only (not nodes)
films: a. immediate series 10’ ankles 15’ knees 20’ thighs 30’ pelvis 45,60, 90’ abdomen 120’ chest, usually shows thoracic duct, ± supraclavicular nodes b. 24 hr series c. delayed series 2, 4, 8 weeks
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contraindications: infection chronic lung disease => consider unilateral injection right-to-left shunt / pulmonary AVM less than 3/52 after radio- or chemotherapy
complications: allergy, infection and emboli multiple small pulmonary emboli lead to transient reduction in KCO right to left shunt/radio-Rx to lungs < 3/52 => systemic emboli lymphatic obstruction => hepatic emboli intravenous injection => globulation (caviar sign)
more and more replaced by Tc-micro-colloid scan
Myelography Indications: absence / CI to MRI
root avulsion disc prolapse acute cord trauma pre-surgery acute cord compression intraxial SOL
Suboccipital puncture only indicated for spinal block, otherwise CM is run up from lumbar approach Ionic CM cause arachnoiditis and fits, in particular under anti-epileptic medication Maximum intrathecal dose of iodine = 3g (=> 10 ml LOCM 300)
GI-tract Ba-meal 200-250% w/v, inhomogenous particle size as flocculation not a problem due to short examination time
small particle sizes required to demonstrate areae gastricae high kVp => reduce movement artefact + improve contrast
Ba-follow through
40-60% w/v Small bowel enema
20-40% w/v tube inserted in right elevated decubitus as rising air distends pylorus / right side down if weighted tip 1200 ml of at 75 ml/min transit can be accelerated with cold saline
Barium-enema 100% w/v delay after colonic biopsy 3 days for superficial Bx 10 days after deep Bx
Cholangiography
a. oral cholecystography CM not substituted at 5C-atom => high protein binding => hepatic uptake; uricosuric, displaces other drugs (i.e. digoxin) supine oblique shows neck and body, prone oblique shows fundus GB contracts 10-20 min. after fatty meal ipodate (Biloptin®): after 1-5 hrs in bile ducts, after 14-19 hrs in gall bladder => 2 doses given at -3 and -15 hrs b. intravenous cholangiogram dimeric CM, active uptake reaches saturation => 1h infusion glucagon increases transport into bile, practical value dubious reflux into duodenum post-cholecystectomy can simulate gallbladder filling stratification in gallbladder represents layering of old and new bile => late erect film c. ERCP contraindications: pseudocysts, thoracic aortic aneurysm, not duodenal diverticula 2-5 ml CM for pancreatic duct, up to 3 mm acute pancreatitis in 1% d. intraoperative stationary grid/gridded cassette intrahepatic biliary tree should be demonstrated e. T-tube
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at 7.-10. days post-op., antibiotic cover not required right hepatic duct easier to demonstrate than left, distal bile duct should be seen f. percutaneous transhepatic, PTCA mid-axillary line, undilated biliary systems can be demonstrated in > 60% gallbladder is often not seen
Urinary tract Intravenous Urogram, IVU Dynamic study for assessment of anatomy as well as function
Indications: haematuria, obstruction, colic Contraindications: allergy, myeloma mortality rate: 1:40.000
Technique: 6-8 hour fast unless renal impairment, dehydration does not improve nephrogram as CM freely filtrated 300 mg Iodine / kg as quick bolus (the faster the injection the more likely are side-effects) 50ml of Iohexol 350 deliver 17.5g total iodine = 230 mg/kg for 70 kg 50ml of Diatrizoate 370 deliver 18.5g total iodine = 265 mg/kg for 70 kg films: 1. control film, full length ± oblique views for calculi 2. +7 min. film, can be renal area only => renal outline, position, size, parenchyma, early excretion 3. +15 min. compression film (renal area only) => filled calyceal system if renal contours not demonstrated, consider tomogram 8-10 cm / USS 4. immediate release film (full length) => filled ureters ± prone film 5. if indicated post-mictuition film of bladder (incl. ureters if obstruction / reflux)
Children: gas-filled stomach as window for visualising kidneys High dose IVU
in renal failure, double dose contrast (600mg/kg), immediate tomograms Transplant kidney
for haemorrhage, urinary leak, lymphocele, obstruction same dose (300mg/kg), control tomograms often required
Antenatal USS Estimation of gestational age
up to 12 weeks crown-rump length, afterwards unreliable as spine flexed after 12/40: BPD or femur length
Visualisation limb buds 5/40 yolk sac 5/40 - 12/40 foetal heart 6/40 skull 8/40 head / BPD > 10/40 lateral ventricles 12/40 localisation of placenta > 12/40 (filled) bladder 16/40
Ossification centres calcaneus 24-26/40 talus 28/40 distal femur 36/40 prox. tibia 38/40
Normal measurements BPD 44 ±2 mm 18/40 femur length 28 ±2 mm 18/40 ventricular atrium < 10 mm 15-40/40 cisterna magna a.p. 3-10 mm 15-40/40 cerebellum width in mm equals age in weeks up to 3rd trimester
Genito-urinary tract mesonephros foetal excretory system => metanephric systems = permanent kidneys
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mesonephric duct Wolffian duct => ureters and trigone vesicae => ductus deferens/epidydimis, seminal vesicles post. outgrowth = ureteric bud => collecting system required to stimulate evolution of metanephric system (no ureter => no kidney) paramesonephric duct Müllerian duct => uterus and upper vagina => appendix testis, prostatic utricle
Horse-shoe kidney 1: 400 - 1: 600 Pituitary anterior lobe => Rathke’s pouch (ectoderm)
post. lobe => diencephalon Abnormality scan 18-20/40 high sensitivity (75-85%), excellent specificity ( 99%) Heart four chambers, septum and valve motion should be visualised, right ventricle thicker than left
Abdomen section including stomach, portal vein and chord insertion Gastroschisis
small bowel prolapses into amniotic fluid through paraumbilical abdominal wall defect physiological < 11/40, delayed return to abdominal cavity is associated with malrotation
Exomphalos prolapse of bowel ± liver into umbilical chord associated with neural tube defects, bad prognosis
Single umbilical artery - diabetes mellitus - twins - cardiac and other abnormalities
Brain Choroid plexus cysts
associated with chromosomal abnormalities i.e. 18³ Neural tube defects
failure of fusion of the invaginated mid-line ectoderm to form the neural tube and its protecting structures wide spectrum: spina bifida - meningocele - myelomeningocele - anencephaly intracranial signs are banana-sign of cisterna magna as cerebellum oval rather than dumbbell shaped lemon-sign of skull = not uniformly oval in cross-section, but frontal peak hydrocephalus if associated Chiari-malformation (= herniation of cerebellar tonsils) compresses IVth ventricle
Anencephaly 1:1000, f:m = 4:1, raised AFP no development of Tel- and Dienecephalon absence of cranial vault with developed facial bones => “frog eyes”
Dandy-Walker syndrome defect of development of midline structures vermis-agenesis => IV ventricle communicates with cisterna magna between the unconnected cerebellar hemispheres, associated with other midline defects
Holoprosencephaly rare defect of midline structure development, absence of diencephalon, failure of cleavage of telencephalon familial, associated with chromosomal abnormalities (15³, 18³) - single, large mid-line ventricle - absence of falx and lat. ventricles <=> DD: Dandy-Walker, subarachnoid cyst - facial anomalies
Signs of foetal death
absence of heart beat spalding-sign: overlapping of sutures air within cerebral ventricles air within bowel