1 fluoroscopy intro to equipment rt 244 fall 2008-10 week 1 wed- continued ref: fluoroscopy –...

1

Fluoroscopy Intro to EQUIPMENT

RT 244

FALL 2008-10

Week 1

Wed- CONTINUED

Ref: Fluoroscopy – Bushong’s Ch. 24

2

Basic Componets of “old” Fluoroscopy “Imaging Chain”

Fluoro TUBE

Primary

Radiation PATIENT

EXIT Radiation

Image Intensifier

ABC Image Recording Devices

Fiber Optics OR

105 Photospot

CINE

Cas

sett

e

VIDICON

Camera Tube

CONTROL

UNITTV

LENS

SPLIT

3

Conventional I I system

4

IMAGE INTENSIFIER

5

The anode of the II

The anode is about 20” away from these electrons so what will help move the E’s?

Electrostatic lenses have a negative charge to repel the negative electrons and push them to the anode and focus them to a narrow beam*

Anode has a hole in the middle of it allowing electrons to pass through and hit the output phosphor made of zinc cadmium sulfide*

The electrons are carrying the latent image and when they hit the output phosphor they are turned into light again

6

Anode and Output Screen

Anode Positively charged 25 kVp Hole in center allows electrons to pass through to

output screen OUTPUT SCREEN

Usually 1 inch in diameter Zinc cadnium sulfide coating Changes electrons back to LIGHT

7

Image IntensifierPROPERTIES

Image Quality

Contrast

Resolution

Distortion

Quantum mottle

8

Contrast

Controlled by amplitude of video signal Affected by:

Scattered ionizing radiation Penumbral light scatter

9

Veiling glare Scatter in the form of

x-rays, light & electrons can

reduce contrast of an image

intensifier tube.

10

Resolution

Video viewing Limited by 525 line raster pattern of monitor

Newer digital monitors 1024 - better resolution

MORE ON THIS LATER IN THE LECTURE

11

Image distortion

PINCUSHION EFFECT

12

Shape Distortion

Geometric problems in shape of input screen Concave shape helps reduce shape distortion,

but does not remove it all Vignetting or pin cushion effect

Vignetting

FALL-OFF OF BRIGHTNESS AT PERIPHERY (EDGES) OF THE IMAGE

13

VIGNETTING…….

Darkness on edges (falloff of brightness)

14

Size Distortion

Affected by same parameters as static radiography Primarily OID Can be combated by bringing image intensifier as

close to patient as possible

15

ABC

16 Basic Componets of “old”

Fluoroscopy “Imaging Chain”Fluoro TUBE

Primary

Radiation PATIENT

EXIT Radiation

Image Intensifier


Fiber Optics OR

105 Photospot

CINE

Cas

sett

e

VIDICON

Camera Tube

CONTROL

UNITTV

LENS

SPLIT

17

Brightness Control

Automatic brightness stabilization Automatic adjustments made to exposure factors

by equipment Automatic gain control

Amplifies video signal rather than adjusting exposure factors

18

BRIGHTNESS CONTROL

ABC ABS AEC ADC

MAINTAINS THE BRIGHTNESS OF THE IMAGE – BY AUTOMATICALLY ADJUSTING THE EXPSOURE FACTORS (KVP &/OR MAS) FOR THICKER PARTS

SLOW RESPONSE TIME - IMAGE LAG

19

ABC

Automatic brightness control allows Radiologist to select brightness level on screen by ↑ kVp or ↑ mAs

Automatic dose control Located just beyond the Output Phosphor

Will adjust according to pt thickness

20 Automatic Brightness Control

Monitoring Image Brightness Photocell viewing (portion of) output phosphor TV signal (voltage proportional to brightness)

Brightness Control: Generator feedback loop kVp variable mA variable/kV override kV+mA variable Pulse width variable (cine and pulsed fluoro)

21

Quantum Mottle

Blotchy, grainy appearance Caused by too little exposure Most commonly remedied by increasing Ma Controlled by the ABC Affected by too little technique size of patient distance of II to patient size of collimation

22 Fluoroscopic Noise

(Quantum Mottle)

Fluoroscopic image noise can only be reduced by using more x-ray photons to produce image. Accomplished in 3 ways:

Increase radiation dose (bad for patient dose) Frame-averaging:

creates image using a longer effective time Can cause image lag (but modern methods

good) Improve Absorption Efficiency of the input

phosphor

23 KEEP I.I. CLOSE TO PATIENT

reduces beam on time

25

Units of measurement

INPUT PHOSPHOR – IS MEASURED IN _________________________________

OUTPUT PHOSPHOR IS MEASURED IN ______________________________

26

Units of measurement

INPUT PHOSPHOR – IS MEASURED IN

Milliroentgens mR

OUTPUT PHOSPHOR IS MEASURED IN

CANDELAS (LIGHT)

VIEWBOXES ARE MEASURED IN: lamberts (light)

27

Fluoroscopic Imaging

28

Coupling I.I. to TV Monitor

2 Methods: Fiber optics directly to T.V. camera. Lens system which utilizes auxiliary imaging

devices.

30

Directly to T.V.

Only cassettes can be used.

31

Beam splitting mirror



Primary

Radiation PATIENT

EXIT Radiation

Image Intensifier


Fiber Optics OR

105 Photospot

CINE

Cas

sett

e

VIDICON

Camera Tube

CONTROL

UNITTV

LENS

SPLIT

34

Beam splitting mirror

Often a beam splitting mirror is interposed between the two lenses.

The purpose of this mirror is to reflect part of the light produced by the image intensifier onto a 100 mm camera or cine camera.

Typically, the mirror will reflect 90% of the incident light to other RECORDING DEVICES

and transmit 10% onto the television camera*. *TV MONITOR is the weakest link (low resolution)

35 Viewing Fluoroscopic Images

37

Lenses / Mirrors

Used to direct image to recording devices Several mirrors in a series and angled - the

last mirror is outside the II for the operator to view

Image decreases as it is projected from 1 mirror to the next

Only 1 person can view image

38

RECORDING THE IMAGE

STATIC IMAGES

DYNAMIC IMAGES



Primary

Radiation PATIENT

EXIT Radiation

Image Intensifier


Fiber Optics OR

105 Photospot

CINE

Cas

sett

e

VIDICON

Camera Tube

CONTROL

UNITTV

LENS

SPLIT

40 Recording the Fluoroscopic

Image

STATIC IMAGES Cassettes 105 mm chip film = 12 frames per second

Digital fluoroscopy DYNAMIC VIEWING: Cine film Videotape

41 Recording Fluoroscopic

Images

42

IMAGE RECORDING

OLD II - ONLY FIBER OPTICS –NO LENS SPLITTER TO OTHER RECORDING DEVICES

ONLY RECORED IMAGE ON SPOT CASSETTES (9X9 ONLY)

NEWER - TAKES CASSETTES or uses /105 PHOTOSPOT / VIDEO/ CINE

NEWEST = USES DIGITAL !!!!!!!!! (but the tests* still have all of it!)



Primary

Radiation PATIENT

EXIT Radiation

Image Intensifier


Fiber Optics

105 Photospot

CINE

Cas

sett

e

VIDICON

Camera Tube

CONTROL

UNITTV

LENS

SPLIT

44

Fluoroscopy mA

Low, continuous exposures .05 – 5 ma (usually ave 1 – 2 ma)

Radiographic Exposure for cassette spot filmsmA increased to 100 – 200

mA

45

RECORDING IMAGES

OLD (Smaller) II with fiber optic

ONLY RECORDING WAS CASSETTE

CASSETTE “SPOT” IMAGES TAKEN DURING FLUORO PROCEDURE VERY OLD 9X9 inch cassettes Later could take up to 14 x 14 inches

46

Cassettes

Standard size - 9” x 9” (old) NOW CAN TAKE UP TO 14X14 Stored in lead-lined compartment until ready

for exposure When exposure is made, mA is raised to

radiographic level Multiple image formats

49

Image recording

Cassette loaded spot film Where is the tube? How should you put the IR into the II slot?You can format the image, 2 on 1, 4 on 1 or 1 on 1Cassette loaded spot film increases patient dose



Primary

Radiation PATIENT

EXIT Radiation

Image Intensifier


Fiber Optics OR

105 Photospot

CINE

Cas

sett

e

VIDICON

Camera Tube

CONTROL

UNITTV

LENS

SPLIT

53 70 & 105 PHOTOSPOT

(CAMERA)

Photo spot camera will take the image right off the output phosphor

This requires less patient dose 70 & 105 mm roll film

54 CASSETTE SPOT FILMING

vs PHOTOSPOT FILMING

First type of recording used 9x9 cassettes then later up to 14x 14 9 on 1, 4 on 1, 2 on 1 Delay while filming (anatomy still moving) Radiographic mA - must boost up to 100 – 200 mA for filming And moving cassettes around inside tower Higher patient dose Replaced by Photospot (f/sec) filming

56 CASSETTE SPOT FILMING

vs PHOTOSPOT FILMING

Photospot (f/sec) filming – Set at control panel from 1 f/sec – 12 f/sec Used for rapid sequence:

Upper Esophogram Voiding Cystourethrograms (Peds)

Lower patient dose

57 Recording the Fluoroscopic

Image

Dynamic systems Cine film systems Videotape recording Static spot filming systems

58 TV camera and video signal

& Recording the image

The output phosphor of the image intensifier is optically coupled to a television camera system.

Beam splitter – is a partially reflective mirror. A pair of lenses focuses the output image onto the

input surface of the television camera. Often a beam splitting mirror is interposed between

the two lenses. The purpose of this mirror is to reflect part of the light

produced by the image intensifier onto a 105 mm PHOTOSPOT camera or cine camera.

59

VIDICONVIDICON

FILMFILM PMPM REFERENCEREFERENCEkVkV

CONTROLLERCONTROLLER

X Ray TUBEX Ray TUBE kVkV

GENERAL SCHEME OF FLUOROSCOPYGENERAL SCHEME OF FLUOROSCOPY

CINE - USED FOR CARDIAC CATH

60

Cine Film Systems

Movie camera intercepts image 16 mm and 35 mm formats Record series of static exposures at high speed 30 – 60 frames per second

Offer increased resolution At the cost of increased patient dose

61

Cinefluorgraphy aka CINE

35 or 16 mm roll film (movie film) 35 mm ↑ patient dose / 16 mm – higher quality images produced 30 f/sec in US – (60 frames / sec)

THIS MODALITY = HIGHEST PATIENT DOSE (10X greater than fluoro)

(VS SINGLE EX DOSE IS ↓)

62 Cine

Cinefluorography is used most often in cardiology and neuroradiology.

The procedure uses a movie camera to record the image from the image intensifier.

These units cause the greatest patient doses of all diagnostic radiographic procedures, although they provide very high image quality.

The high patient dose results from the length of the procedure and relatively high inherent dose rate.

For this reason special care must be taken to ensure that patients are exposed at minimum acceptable levels.

Patient exposure can be minimized in a number of ways. The most obvious means of limiting exposure is to limit the time the beam is on.

CINE - 2mR per frame (60f/sec)

400 mr per “look”

63

More on Cine

Synchronization Framing frequency F-number of the optical system Framing and patient dose

64

Synchronization

Camera shutters and x-ray pulsed fluoro happen at the same time

Only exposes pt when shutter is open to record image

Patient radiation dose ↑ as #/f/sec ↑

(filming a TV show – pattern seen)

65

F-number of the optical system

Speed of any given camera system The amount of light made available to the

lens

66 Framing and patient dose

syll = Pg 31

The use of the available film area to control the image as seen from the output phosphor. Underframing Exact Framing, (58 % lost film surface) Overframing,(part of image is lost) Total overframing

67 OVERFRAMING vs Exact

Framing

Also related to Radiation Safety………………

68

Framing frequency

Number of frames per second Cine – division of 60 (7.5, 15,30,90,120) Organ if interest determines f/s rate Patient exposu

69

More on Safety later….

70 RECORDING DEVICES

RESOLUTION P 542 (3rd ed)

OPTICAL MIRROR – BEST BUT NOT PERMANENT RECORDING MEDIUM

SPOT FILM CASSETTES 6LP/MM PHOTO SPOT 105 / 70 CINE 35 MM / 16 MM DIGITAL (?) (VS FILM) VIDEO – VIEWING REALTIME VIDEO TAPE - PLAYBACK

72

Line pair gauges

73Line pair gauges

GOOD RESOLUTION POOR RESOLUTION

74

Video disc

This technique is referred to as electronic radiography.

Fluoroscopic radiation continues only long enough to build up a useful image on the display monitor.

The image is stored as a single television frame on the video disc recorder.

There is about a 95% reduction in patient dose.

75

Video tape

Utilizes VHS or high-resolution tapes. Patient’s exposure to radiation is not

increased. Used for barium swallows.

76

Image Quality - Review

Terms that are necessary to know: Vignetting is the loss of brightness at the

periphery of the II due to the concave surface Pincushion effect is the drop off at the edges of

the II due to the curved surface Quantum mottle is the grainy appearance on the

image due to statistical fluctuations The center of the II will always have the best

resolution. Lag is the blurry image from moving the II too

fast

77

OVERFRAMING vs Exact Framing

78

Monitoring

The output phosphor of the II is connected directly to a TV camera tube when the viewing is done through a television monitor.

The most commonly used camera tube - vidiconInside the glass envelope that surrounds the TV

camera tube is a cathode, an electron gun, grids and a target.

Past the target is a signal plate that sends the signal from the camera tube to the external video device

79

VIDEO/CAMERA TUBE

PLUMICON, VIDICON, ORTHOCON VIDICON MOST COMMOM ORTHOCON – VERY $$$$ PLUMICON – BETTER RESOLUTION TRANSFERS IMAGE FROM OUTPUT

PHOSPHOR TO TV MONITOR CONNECTED BY FIBER OPTICS

80

VIDEO/CAMERA TUBE

PLUMICON, VIDICON, ORTHOCON, CCD’s TRANSFERS IMAGE FROM OUTPUT PHOSPHOR

TO TV MONITOR CONNECTED BY FIBER OPTICS or Optical Lens

VIDICON- MOST COMMOM PLUMICON – BETTER RESOLUTION CCD – Charged Coupling Devices ORTHOCON – VERY $$$$

81

VIDEO/CAMERA TUBE VIDICON MOST COMMOM

– good resolution with moderate lag – ok for organs Uses ANTIMONY TRISULFATE

PLUMICON (a modification of Vidicon) – BETTER RESOLUTION / (↓ dose) Better for moving part like the heart –faster response time High performance, lag may improve, but ↑quantum mottle Uses LEAD OZIDE

ORTHOCON – VERY $$$$ - Larger (Not used)BEST RESOLUTION WITH NO LAG Functions as both II and pick up tube

CCD – smaller & longer life, very little image lag

82

Type of TV camera VIDICON TV camera

improvement of contrast improvement of signal to noise ratio high image lag

PLUMBICON TV camera (suitable for cardiology) lower image lag (follow up of organ motions) higher quantum noise level

CCD TV camera (digital fluoroscopy) digital fluoroscopy spot films are limited in resolution,

since they depend on the TV camera (no better than about 2 lp/mm) for a 1000 line TV system

83

TV camera and video signal (II)

Older fluoroscopy equipment will have a television system using a camera tube.

The camera tube has a glass envelope containing a thin conductive layer coated onto the inside surface of the glass envelope.

In a PLUMBICON tube, this material is made out of lead oxide, whereas antimony trisulphide is used in a VIDICON tube.

84 Vidicon (tube) TV Camera

86

camera tube have a diameter of approximately

1 inch and a length of 6 inches.

88

Parts of the camera tube

Glass envelope Electron gun (Cathode) Control grid Electrostatic grids Target

89

Camera Tube steps

Light is received by the camera tube. The light from the II is received at the face plate of

the target assembly. Electrons are formed into an electron beam (by the

control grid) at the electron gun. Electrons are burned off by thermionic emission

then focused and accelerated to the target. (made of antimony trisulfide)

90

Target of the Camera Tube

91

The electrons scan the signal plate similar to reading a page.

Starting in the upper left across to the right, then back to the left to right.

This is called an active trace. The movement of the electron beam

produces a RASTER pattern. The same pattern occurs in the TV

monitor.

92

The signal plate sends the electrical video signal to the control unit which amplifies the signal and synchronizes the pulses between the camera tube and the TV monitor.

This synchronization

93 Vidicon Target Assembly

94

Viewing Systems

Video camera charge-coupled device (CCD) Video monitor Digital

95

Video Viewing System

Closed circuit television Video camera coupled to output screen and

monitor Video cameras

Vidicon or Plumbicon tube CCD

96Synchronization (Sync Signals)

97

TV camera and video signal (V)

On most fluoroscopy units, the resolution of the system is governed by the number of lines of the television system.

Thus, it is possible to improve the high contrast resolution by increasing the number of television lines.

Some systems have 1,000 lines and prototype systems with 2,000 lines are being developed.

98 TV Monitor

99

TV MONITOR

CRT – Cathode Ray Tube Much larger than camera tube – but similar

function The electrons are synchronized by the control

unit – so they are of the same intensity and location as the electrons generated by the pick up (camera) tube.

100

TV Monitor

The TV monitor contains the picture tube called cathode ray tube (CRT).

It works like the camera tube. With an electron gun and control grids the

electron beam is fired toward the anode. The TV screen contains small fluorescent

crystals

101

Video Field Interlacing

102 Different types of scanning

INTERLACED SCANNING

PROGRESSIVESCANNING

12 2

14

4 16

18 6

1

820

13

15

17

10

11

3

21

19

5

7

9

35

1816141210 8 6 4 2

79

11131517

1

625 lines in 40 msi.e. : 25 frames/s

103

Line pair gaugesGOOD RESOLUTION POOR RESOLUTION

6 LP/MM AT SPOT CASSETTE 2 LP/MM AT TV

104

Two fields = a frame (525 lines) It take 1/30 of a second. To prevent flicker, two fields are interlaced

to form on television frame. There are 60 fields and 30 frames per

second. The eye cannot detect flickering above 20

frames/sec.

106

RASTER Pattern

The electron beam moves in the same raster pattern as in the camera tube.

The signal consists of many individual pulses corresponding to the individual location on the camera tube target.

The varying voltage pulses are later reassembled into a visible in by the TV monitor.

107

TV RESOLUTION-Vertical

Conventional TV: 525 TV lines to represent entire image. Example: 9” intensifier (9” FOV)

1) 9” = 229 mm

2) 525 TV lines/229 mm = 2.3 lines/mm

3) Need 2 TV lines per test pattern line-pair

4) (2.3 lines/mm) /2 lines/line-pair = 1.15 lp/mm

Actual resolution less because test pattern bars don’t line up with TV lines. Effective resolution obtained by applying a Kell Factor of 0.7.

Example: 1.15 x 0.7 Kell Factor = 0.8 lp/mm

108

Kell Factor

The ability to resolve objects spaced apart in a vertical direction.

More dots = more scan lines = more/better resolution

Kell factor for 525 line system is 0.7

109

KELL FACTOR

VERTICAL RESOLUTIONABILITY TO RESOLVE OBJECTS SPACED APART IN A VERTICAL DIRECTION

MORE DOTS(GLOBULES) = MORE SCAN LINES = MORE/BETTER RESOLUTION

RATIO OF VERTICAL RESOLUITON # OF SCAN LINES

KELL FACTOR FOR 525 LINE SYSTEM

IS 0.7

110

TV RESOLUTION-Horizontal

Along a TV line, resolution is limited by how fast the camera electronic signal and monitor’s electron beam intensity can change from minimum to maximum.

This is bandwidth. For similar horiz and vertical resolution, need 525 changes (262 full cycles) per line. Example (at 30 frames/second):

262 cycles/line x 525 lines/frame x 30 frames/second

= 4.2 million cycles/second or 4.2 Megahertz (MHz)

111 Bandpass/Horizantal

Resolution

Horizontal resolution is determined by the bandpass.

Bandpass is expressed in frequency (Hz) and describes the number of times per second the electron beam can be modulated.

The higher the bandpass, the better the resolution

112

TV SYSTEMS

Images are displayed on the monitor as individual frames – which tricks the eye into thinking the image is in motion (motion integration)

15 f/sec – eye can still see previous image

Weakest Link - 2 lp /mm resolution

Real Time

114

Final Image

The result of hundreds of thousands of tiny dots of varying degrees of brightness.

These dots are arranged in a specific patterns along horizontal scan lines.

Usually 525 scan lines. The electron gun within the picture tube scans from

top to bottom in 1/60 of a second, (262 1/2 lines) called a field.

117 TABLE MOVEMENT

horizonatal to upright ~ 30 sec

118

End of Week 1 Day 2

119

Digital Fluoro

120

DIGITAL FLUORO

122

DIGITAL Fluoro System

123

ADC –

ANALOG TO DIGITAL CONVERTER

TAKE THE ANALOG ELECTRIC SIGNAL CHANGES IT TO A DIGITAL SIGNAL

TO MONITOR – BETTER RESOLUTION WITH DIGITAL

UNITS

124

Digital Fluoroscopy

Use CCD to generate electronic signal Signal is sent to ADC Allows for post processing and electronic

storage and distribution

125

Video Camera Charged Coupled Devices (CCD)

Operate at lower voltages than video tubes More durable than video tubes

Semiconducting device Emits electrons in proportion to amount of

light striking photoelectric cathode Fast discharge eliminates lag

126

CCD’s

127 Modern Digital Fluoro System

under table tubes

128

Remote – over the table tube

129

Remote – over the table tube

130

Newer Digital Fluoroscopy

Image intensifier output screen coupled to TFTs

TFT photodiodes are connected to each pixel element

Resolution limited in favor of radiation exposure concerns

131 Digital – CCD

using cesium iodide

Exit x-rays interact with CsI scintillation phosphor to produce light

The light interact with the a-Si to produce a signal

The TFT stores the signal until readout, one pixel at a time

132

CsI phosphor light detected by the AMA of silicon photodiodes

135

Digital Uses Progressive Scan

1024 x 1024 Higher spatial resolution As compared to 525

8 images/sec (compared to 30 in 525 system)

136

DSA & POSTPROCESSING

137

DSA

139

Mobile C-arm Fluoroscopy

141 Fluoro & Rad

Protection INTRO RHB

142

Regulatory Requirements

1. Regarding the operation of fluoroscopy units

2. Regarding personnel protection

3. Regarding patient protection

143 Fluoroscopic Positioning

Previewing

Radiographers are trained in positioning Unnecessary radiation exposure to patient is

unethical Fluoroscopic equipment should not be used

to preview patient’s position

144

Patient Protection

Tabletop exposure rate Maximum 10 R/min Typically 1 – 3 R/min

Some books ave is 4 R/min **

145

Patient Protection

Minimum source-to-skin distance 12” for mobile equipment 15” for stationary systems

Audible alarm at 5 mins. Same rules for collimation

146

Patient Protection

Typical exposure rates Cinefluorography

7.2 R/min Cassettes

30 mR/exposure 105 mm film

10 mR/exposure

147

Protection of Radiographer and Radiologist

Single step away from the table decreases exposure exponentially

Bucky slot cover Lead rubber drape Radiologist as shielding

148

Protection of Others

Radiographer’s responsibility to inform others in the room to wear lead apron

Do not initiate fluoroscopy until all persons have complied

149

PUBLIC EXPOSURE

10 % OF OCCUPATIONAL NON MEDICAL EXPOSURE.5 RAD OR 500 MRADUNDER AGE 18 AND STUDENT.1 rem 1 mSv

150

COLLIMATION

The PATIENT’S SKIN SURFACE SHOULD NOT BE CLOSER THAN

___________ CM BELOW THE COLLIMATOR?

____________ INCHES?

15 cm / 6.5 inches

151

Protection

Lots to remember in the summer, for right now:1. Tube in never closer to the patient than 15” in

stationary tubes and 12” with a C arm2. As II moves away from the patient the tube is being

brought closer3. Bucky tray is connected to a lead shield called the

Bucky slot cover. It must be 0.25 mm Pb4. There should be a protective apron of at least 0.25

mm Pb that hangs down from the II5. Every machine is required to have an audible timer

that signals 5 minutes of fluoroscopy time6. Exposure switch must be a “dead man” type

152

Regulations about the operation

Fluoroscopic tubes operate at currents that range from0.5 to 5 mA with 3 the most common

AEC rate controls: equipment built after 1974 with AEC shall not expose in excess of 10 R/min; equipment after 1974 without AEC shall not expose in excess of 5 R/min

153

Other regulations

Must have a dead man switch Must have audible 5 min. exposure timer Must have an interlock to prevent exposure without

II in place Tube potential must be tested (monitored)weekly Brightness/contrast must be tested annually Beam alignment and resolution must be tested

monthly Leakage cannot exceed 100mR/hr/meter

154

Fluoroscopy exposure rate

For radiation protection purposes the fluroscopic table top exposure rate must not exceed 10 mR/min.

The table top intensity should not exceed 2.2 R/min for each mA of current at 80 kVp

155

Patient Protection

1. A 2 minute UGI results in an exposure of approximately 5 R!!

2. After 5 minutes of fluoro time the exposure is 10-30 R

3. Use of pulsed fluoro is best (means no matter how long you are on pedal there is only a short burst of radiation)

4. ESE must not be more than 5 rads/min

156

Rad Protection

Always keep the II as close to the patient as possible to decrease dose

Highest patient exposure happens from the photoelectric effect (absorption)

Boost control increases tube current and tube potential above normal limits Must have continuous audible warning Must have continuous manual activation

158

ESE FOR FLUORO

TLD PLACED AT SKIN ENTRACE POINT 1 – 5 R/MINUTE AVE IS 4 R/MIN

INTERGRAL DOSE – 100 ERGS OF TISSUE = 1 RAD EXPOSURE OR 1 GM RAD = 100 ERGS

159

SSD – TUBE TO SKIN DISTANCE

FIXED UNITS18” PREFERRED15 “ MINIMUM

MOBILE UNITS ( C-ARMS)12’ MINIMUM

160

PATIENT PROTECTION

LIMIT SIZE OF BEAM BEAM ON TIME DISTANCE OF SOURCE TO SKIN PBL FILTRATION (2.5 mm Al eq) @ 70 SHEILDING SCREEN/FILM COMBO

162

GONAD SHIELDING

MUST BE . 5 MM OF LEAD MUST BE USED WHEN GONADS WILL LIE

WITHING 5 CM OF THE COLLIMATED AREA (RHB)

KUB. Lumbar Spine Pelvis male vs female shielding

163

Gonad shielding & dose

♀ receive 3x more dose than

♂ for pelvic x-rays

1 mm lead will reduce exposure

(primary) by about 50% ♀ by about 90 – 95 % ♂

165

KEEP I.I. CLOSE TO PATIENT

166 Over vs under the table

fluoro tubes

167 Framing and patient dose

syll = Pg 31

The use of the available film area to control the image as seen from the output phosphor. Underframing Exact Framing, (58 % lost film surface) Overframing,(part of image is lost) Total overframing

168

EXPOSURE RATES FLUORO

MA IS 0.5 MA TO 5 MA PER MIN AVE DOSE IS 4 R / MIN

IF MACHINE OUTPUT IS 2 R/MA/MIN = WHAT IS PT DOSE AT 1.5 MA FOR 5 MIN STUDY?

15R

169

EXPOSURE RATES FOR FLUORO

CURRENT STANDARD 10 R/MIN (INTENSIFIED UNITS) HLC: BOOST MODE 20 R/MIN OLD (1974) NO ABC NON IMAGE INTES 5 R/MIN

170

DOSE REGULATIONS

BEFORE 1974 - AT TABLETOP 5R/MIN (WITHOUT AEC) 5R/MIN (WITHOUT AEC) – BOOST MODE

After 1974 with AEC 10 R/MIN 20R/MIN BOOST

171

RADIATION PROTECTIONThe Patient is the largest scattering object

Lower at a 90 DEGREE ANGLE from the patient + PRIMARY BEAM

AT 1 METER DISTANCE -1/1000 OF INTENSITY

PRIMARY XRAY or 0.1%

172

BUCKY SLOT COVER.25 MM LEAD

173

Bucky Slot Cover

174

ISOEXPOSURE CURVES

175

PERSONNEL PROTECTION SCATTER FROM THE PATIENT TABLE TOP, COLLIMATOR, TUBE

HOUSING, BUCKY

STRAY RADIATION – LEAKAGE OR SCATTER RADIATION

176

TOWER CURTAIN

.25 MM LEAD EQ

177

Lead curtain & dose reduction

178

Pulsed Fluoro

Some fluoroscopic equipment is designed for pulsed-mode operation. With the pulsed mode, it can be set to produce less than the conventional 25 or 30 images per second. This reduces the exposure rate.

Collimation of the X ray beam to the smallest practical size and keeping the distance between the patient and image receptor as short as possible contribute to good exposure management.

180

PERSONNEL PROTECTION

STANDING BEHIND A PROTECTIVE PRIMARY (1/16TH pb) BARRIER:

PRIMARY RADIATION EXPOSURE – 99.87% REDUCED

PORTABLE BARRIER = 99 % REDUCTION

181

PERSONNEL PROTECTION

PROTECTIVE APRONS – 0.25 PB = 97% ↓ TO SCATTER 0.5 PB = 99.9% ↓ TO SCATTER THYROID SHEILDS (0.25 & 0.5) GLOVES (0.25 & 0.5)

182 PERSONNEL PROTECTION

MONITORING

FILM BADGE TLD POSL

POCKET DOSIMETER

RING BADGE

183 PERSONNEL PROTECTION

MONITORING

DOSE LIMITS WHOLE BODY EYES EXTREMITIES (BELOW ELBOW/KNEES)

185

Report at least every quarterPreserved for a minimum of 3 years

186

RHB NOTIFICATION (EXP IN 24 HOURS)

(RP Syllabus – pg 68)

IMMEDIATE reporting – WITHIN 24 HOURS TOTAL DOSE OF 25 rems Eye dose – 75 rem Extremity – 250 RADS

OVEREXPOSURE – received w/in 24 hrs

Must be ReportedWITHIN 30 DAYS TOTAL DOSE OF 5 rems Eye dose – 15 rem Extremity - 50 REMS

187

LICENSE RENEWAL

WITHIN 30 DAYS OF EXPRIATION NOTIFICATION OF CHANGE OF ADDRESS

188

100 mRem ( 0.1 rem / (1 msV) @ 30 cm from the source of radiaton

RADIAITON AREA – RHB: 5 mRem ( 0.005 rem / (.05 msV)

@ 30 cm from the source of radiation

PUBLIC 2 mrem per week* (STAT)

HIGH RADIAITON AREA –

189 A “controlled area” is defined

as one

that is occupied by people trained in radiologic safety

that is occupied by people who wear radiation monitors

whose occupancy factor is 1

190

RHB “RULES” RHB RP PG61

LICENTIATES OF THE HEALING ARTS(MD, DO, DC, DPM)

MUST HAVE A RADIOLOGY SUPERVISOR &

OPERATORS PERMIT & CERTIFICATE TO OPERATE OR SUPERVISE THE USE

OF X-RAYS ON HUMANS SUPEVISORS MUST POST THEIR

LICENSES

191

RHB “RULES” RHB RP PG62

ALL XRAYS MUST BE ORDERED BY A PHYSICIAN

VERBAL OR WRITTEN PRESCRIPTION

See Section C – “Technologist Restrictions”

192

DOSE

CINE - 2mR per frame (60f/sec) 400 mr per “look”

193 Declared Pregnant Worker

Must declare pregnancy – 2 badges provided 1 worn at collar (Mother’s exposure) 1 worn inside apron at waist level

Under 5 rad – negligible risk

Risk increases above 15 rad

Recommend abortion (spontaneous) 25 rad

(“Baby exposure” approx 1/1000 of ESE)

www.ntc.gov/NRC/RG/08/08-013.html

194

FLUOROSCOPYEnd of wk 1RT 244 2008

1 fluoroscopy intro to equipment rt 244 fall 2008-10 week 1 wed- continued ref: fluoroscopy –...

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