jp© 1 x - rays wilhelm conrad röntgen 1895 jp© 2 induction coil +ve-ve cathode ray discharge tube...
TRANSCRIPT
![Page 1: JP© 1 X - RAYS Wilhelm Conrad Röntgen 1895 JP© 2 Induction Coil +ve-ve Cathode Ray Discharge Tube ROENTGEN 1895 Wrapped Photographic Plate was EXPOSED](https://reader036.vdocuments.net/reader036/viewer/2022062404/551ad660550346856e8b61d2/html5/thumbnails/1.jpg)
JP©1
X - RAYSX - RAYS
Wilhelm Conrad Röntgen
1895
![Page 2: JP© 1 X - RAYS Wilhelm Conrad Röntgen 1895 JP© 2 Induction Coil +ve-ve Cathode Ray Discharge Tube ROENTGEN 1895 Wrapped Photographic Plate was EXPOSED](https://reader036.vdocuments.net/reader036/viewer/2022062404/551ad660550346856e8b61d2/html5/thumbnails/2.jpg)
JP©2
Induction Coil
+ve-ve
Cathode Ray Discharge Tube
ROENTGEN 1895
Wrapped Photographic Platewas EXPOSED
X – RAYS !!
![Page 3: JP© 1 X - RAYS Wilhelm Conrad Röntgen 1895 JP© 2 Induction Coil +ve-ve Cathode Ray Discharge Tube ROENTGEN 1895 Wrapped Photographic Plate was EXPOSED](https://reader036.vdocuments.net/reader036/viewer/2022062404/551ad660550346856e8b61d2/html5/thumbnails/3.jpg)
JP©3
Early cold cathode X-ray tube
Air at low pressure
0 V 100 kV
cathode anode
![Page 4: JP© 1 X - RAYS Wilhelm Conrad Röntgen 1895 JP© 2 Induction Coil +ve-ve Cathode Ray Discharge Tube ROENTGEN 1895 Wrapped Photographic Plate was EXPOSED](https://reader036.vdocuments.net/reader036/viewer/2022062404/551ad660550346856e8b61d2/html5/thumbnails/4.jpg)
JP©4
Heater current
-ve high voltage +ve
BASIC PRINCIPLE
Anode +ve
Thermionic Emission of Electrons
X-Ray Photons
![Page 5: JP© 1 X - RAYS Wilhelm Conrad Röntgen 1895 JP© 2 Induction Coil +ve-ve Cathode Ray Discharge Tube ROENTGEN 1895 Wrapped Photographic Plate was EXPOSED](https://reader036.vdocuments.net/reader036/viewer/2022062404/551ad660550346856e8b61d2/html5/thumbnails/5.jpg)
JP©5
On Average 99% of each electron’s energy is converted into heat energy.
X-RAYS ARE PRODUCED IN TWO WAYS.
1. A BACKGROUND BREMSSTRAHLUNG SPECTRUM
2. A FINE LINE SPECTRUM
Wavelength range : 10-9 - 10-11 metres
![Page 6: JP© 1 X - RAYS Wilhelm Conrad Röntgen 1895 JP© 2 Induction Coil +ve-ve Cathode Ray Discharge Tube ROENTGEN 1895 Wrapped Photographic Plate was EXPOSED](https://reader036.vdocuments.net/reader036/viewer/2022062404/551ad660550346856e8b61d2/html5/thumbnails/6.jpg)
JP©6
BREMSSTRAHLUNG RADIATION SPECTRUM
ACCELERATING CHARGES RADIATE ELECTROMAGNETIC RADIATION
+
NUCLEUS
When a fast-moving electron swings around a heavily charged nucleus, its acceleration changes rapidly.
BREMSSTRAHLUNG radiation
Eenergyphoton
Photon Energy, E = hf
E
hc
![Page 7: JP© 1 X - RAYS Wilhelm Conrad Röntgen 1895 JP© 2 Induction Coil +ve-ve Cathode Ray Discharge Tube ROENTGEN 1895 Wrapped Photographic Plate was EXPOSED](https://reader036.vdocuments.net/reader036/viewer/2022062404/551ad660550346856e8b61d2/html5/thumbnails/7.jpg)
JP©7
BREMSSTRAHLUNG BACKGROUND SPECTRUM
Many X-Ray wavelengths [ down to a certain minimum ] may be produced by a particular X-Ray tube, depending upon how much of the electron’s energy is converted in this way.
0 2 4 6 8 10λ x 10-11 m
Intensity
50 kV
20 kV
Maximum electron energy available = eV
minhc
hfeV
eV
hcminλmin
![Page 8: JP© 1 X - RAYS Wilhelm Conrad Röntgen 1895 JP© 2 Induction Coil +ve-ve Cathode Ray Discharge Tube ROENTGEN 1895 Wrapped Photographic Plate was EXPOSED](https://reader036.vdocuments.net/reader036/viewer/2022062404/551ad660550346856e8b61d2/html5/thumbnails/8.jpg)
JP©8
FINE [ LINE ] SPECTRUM
DEPENDS UPON THE TARGET METAL IN
THE ANODE
50 kV
0 2 4 6 8 10λ x 10-11 m
Intensity
20 kV
![Page 9: JP© 1 X - RAYS Wilhelm Conrad Röntgen 1895 JP© 2 Induction Coil +ve-ve Cathode Ray Discharge Tube ROENTGEN 1895 Wrapped Photographic Plate was EXPOSED](https://reader036.vdocuments.net/reader036/viewer/2022062404/551ad660550346856e8b61d2/html5/thumbnails/9.jpg)
JP©9
LINE SPECTRUM Produced after an electron knocks out an inner electron from one of the target atoms
NUCLEUS
K
L
M
e
Electrons from a higher energy level can then fall in to a vacant energy level.
Excess energy is lost as an X-Ray photon
e
e
LM EE
hc
KL EE
hc
![Page 10: JP© 1 X - RAYS Wilhelm Conrad Röntgen 1895 JP© 2 Induction Coil +ve-ve Cathode Ray Discharge Tube ROENTGEN 1895 Wrapped Photographic Plate was EXPOSED](https://reader036.vdocuments.net/reader036/viewer/2022062404/551ad660550346856e8b61d2/html5/thumbnails/10.jpg)
JP©10
X-RAY SPECTRUM AS A FUNCTION OF TUBE P.D.
Intensity
Voltage / kV
100 kV 150 kV
![Page 11: JP© 1 X - RAYS Wilhelm Conrad Röntgen 1895 JP© 2 Induction Coil +ve-ve Cathode Ray Discharge Tube ROENTGEN 1895 Wrapped Photographic Plate was EXPOSED](https://reader036.vdocuments.net/reader036/viewer/2022062404/551ad660550346856e8b61d2/html5/thumbnails/11.jpg)
JP©11
ROTATING ANODE X-RAY TUBE
6.3 V A.C.
hot filament
focusing cathode
0 V
100 000Vvacuum
motor stator
motor rotor
ball race bearings
rotating anode
tungsten target
electron beam
X-RAYS
THE ANODE ROTATES AT 3000 RPM
![Page 12: JP© 1 X - RAYS Wilhelm Conrad Röntgen 1895 JP© 2 Induction Coil +ve-ve Cathode Ray Discharge Tube ROENTGEN 1895 Wrapped Photographic Plate was EXPOSED](https://reader036.vdocuments.net/reader036/viewer/2022062404/551ad660550346856e8b61d2/html5/thumbnails/12.jpg)
JP©12
THE ANODE IS ROTATED SO THAT IT DOES NOT MELT.
ROTATING ANODE X-RAY TUBE
THE TUBE IS IMMERSED IN OIL TO ASSIST COOLING.
X-Ray QUALITY [= penetrating power] is increased by increasing the p.d. across the tube.
X-Ray INTENSITY [ number of photons per second] is increased by increasing the filament current.
This is the way in which the exposure time to produce a photographic plate is controlled.
![Page 13: JP© 1 X - RAYS Wilhelm Conrad Röntgen 1895 JP© 2 Induction Coil +ve-ve Cathode Ray Discharge Tube ROENTGEN 1895 Wrapped Photographic Plate was EXPOSED](https://reader036.vdocuments.net/reader036/viewer/2022062404/551ad660550346856e8b61d2/html5/thumbnails/13.jpg)
JP©13
ATTENUATION OF X-RAYS
IN A VACUUM, OR AIR, ATTENUATION OBEYS THE INVERSE SQUARE LAW
IN A MATERIAL OF THICKNESS X metres xeII 0
Where I = the transmitted intensity in Wm-2 , I0 = the incident intensity and
μ = the linear attenuation coefficient.
% t
ran
smis
sio
n 100
50
x
2
1x
xeII 0
the half thickness
![Page 14: JP© 1 X - RAYS Wilhelm Conrad Röntgen 1895 JP© 2 Induction Coil +ve-ve Cathode Ray Discharge Tube ROENTGEN 1895 Wrapped Photographic Plate was EXPOSED](https://reader036.vdocuments.net/reader036/viewer/2022062404/551ad660550346856e8b61d2/html5/thumbnails/14.jpg)
JP©14
x
the half thickness is the thickness of material that halves the X-Ray intensity
2ln
2
1 x
The mass attenuation coefficient, μm, is the attenuation
per unit mass of material.
m where ρ is the density of the material
![Page 15: JP© 1 X - RAYS Wilhelm Conrad Röntgen 1895 JP© 2 Induction Coil +ve-ve Cathode Ray Discharge Tube ROENTGEN 1895 Wrapped Photographic Plate was EXPOSED](https://reader036.vdocuments.net/reader036/viewer/2022062404/551ad660550346856e8b61d2/html5/thumbnails/15.jpg)
JP©15
X-RAY IMAGING X-rays cannot be focused.
They only make shadow images.
We therefore need to produce a point source.
The geometry of the anode restricts the angular beam width to about 17o.
The width of the beam is further limited with strips of lead.
Lead aperture
Lead cone
anode
Narrow X-Ray Beam
![Page 16: JP© 1 X - RAYS Wilhelm Conrad Röntgen 1895 JP© 2 Induction Coil +ve-ve Cathode Ray Discharge Tube ROENTGEN 1895 Wrapped Photographic Plate was EXPOSED](https://reader036.vdocuments.net/reader036/viewer/2022062404/551ad660550346856e8b61d2/html5/thumbnails/16.jpg)
JP©16
X-RAY IMAGING
Lead aperture
Lead cone
anode
Lead GRID absorbs scattered X-Rays
FILM
![Page 17: JP© 1 X - RAYS Wilhelm Conrad Röntgen 1895 JP© 2 Induction Coil +ve-ve Cathode Ray Discharge Tube ROENTGEN 1895 Wrapped Photographic Plate was EXPOSED](https://reader036.vdocuments.net/reader036/viewer/2022062404/551ad660550346856e8b61d2/html5/thumbnails/17.jpg)
JP©17
IMAGE INTENSIFIER TUBE
fluorescent screen A
X R
AY
Sphotocathode anodes fluorescent
screen B
evacuated glass envelope
electrons
to TV camera
Screen A converts X – Rays into light
Light releases photoelectrons from the photocathode
Electrons accelerated by anodes
The energy gained by the electrons increases the intensity produces in screen B by a factor of 100
![Page 18: JP© 1 X - RAYS Wilhelm Conrad Röntgen 1895 JP© 2 Induction Coil +ve-ve Cathode Ray Discharge Tube ROENTGEN 1895 Wrapped Photographic Plate was EXPOSED](https://reader036.vdocuments.net/reader036/viewer/2022062404/551ad660550346856e8b61d2/html5/thumbnails/18.jpg)
JP©18
Barium sulphate is used for X-rays of the digestive system. It is given as a white liquid drink (barium meal) or into the back passage (barium enema). X-rays cannot go through it, so when the X-ray pictures are taken, the outline of the stomach or bowel shows up on the X-ray.
Contrast Media
![Page 19: JP© 1 X - RAYS Wilhelm Conrad Röntgen 1895 JP© 2 Induction Coil +ve-ve Cathode Ray Discharge Tube ROENTGEN 1895 Wrapped Photographic Plate was EXPOSED](https://reader036.vdocuments.net/reader036/viewer/2022062404/551ad660550346856e8b61d2/html5/thumbnails/19.jpg)
JP©19
X – Ray source moves around the circular tube sending X - Rays through the patient in a fan shaped beam.
X –Ray detector moves around in time with the source and measures the X – Ray strength in each position.
![Page 20: JP© 1 X - RAYS Wilhelm Conrad Röntgen 1895 JP© 2 Induction Coil +ve-ve Cathode Ray Discharge Tube ROENTGEN 1895 Wrapped Photographic Plate was EXPOSED](https://reader036.vdocuments.net/reader036/viewer/2022062404/551ad660550346856e8b61d2/html5/thumbnails/20.jpg)
JP©20
Each time the x-ray tube and detector make a 360 degree rotation and the x-ray passes through the patient's body, the image of a thin section is acquired.
During each rotation, the detector records about 1,000 images (profiles) of the expanded x-ray beam.
Each profile is then reconstructed by a computer into a two-dimensional image of the section that was scanned.
Computed Tomography Imaging (CT Scan, CAT Scan)