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Fluoroscopy Review

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Fluoroscopy Review RT 255 Revised May 2008 Basic Imaging Chain Conventional Fluoroscopic Unit Conventional fluoroscopy User viewed faint image on screen User in ... – PowerPoint PPT presentation

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Title: Fluoroscopy Review


1
Fluoroscopy Review
  • RT 255

Revised May 2008
2
Basic Imaging Chain
3
Conventional Fluoroscopic Unit
  • Conventional fluoroscopy
  • User viewed faint image on screen
  • User in direct path of beam
  • Very high dose to user and patient
  • Excellent resolution
  • No longer used

4
Conventional Fluoroscopy
5
Conventional Fluoroscopy
30 min for dark adaptation RODS or CONES VISION?
6
Light Levels and Fluoroscopy
7
Image Intensified Fluoroscopy
  • Electronic conversion of screen image to light
    image that can be viewed on a monitor
  • ? resolution
  • ? dose

8
The image intensifier (I.I.)
I.I. Input Screen
Electrode E1
Electrode E2
Electrode E3
Electrons Path
I.I.Output Screen
Photocathode

9
Modern fluoroscopic system components
10
Modern Fluoroscopic Unit
11
Image intensifier systems
12
Image Intensifier
  • VACUUM TUBE
  • ENCASED IN A LEAD HOUSING
  • 2MM PB
  • (PRIMARY BARRIER)

13
Functioning of Image Intensifier
14
IMAGE INTENSIFIER
  • INPUT PHOSPHOR CESIUM IODIDE
  • PHOTOCATHODE (LIGHT TO ES)
  • ELECTOSTATIC LENSES
  • FOCUSES AND ACCELERATES THE E
  • INTENSIFIES LIGHT BRIGHTNESS GAIN (BG)
  • BG MG X FG

15
II Image Intensifier
  • The input phosphor converts x-ray to light
  • Light from the input phosphor is sent to the
    photocathode made of cesium and antimony
    compounds
  • Photocathode turns light into electrons (called
    photoemission)
  • Now we have electrons that need to get to the
    anode

16
Image Intensifier Tube
  • Vacuum diode tube
  • 1. Input phosphor (CsI)
  • X-rays ? light
  • 2. Photocathode
  • Photoemission
  • Light ? electron beam
  • 3. Electrostatic lenses
  • Maintain minify e-
  • 4. Anode
  • Attracts e- in beam
  • 5. Output phosphor (ZnS-CdS)
  • e- ? light

17
Multi-field II Units
  • II that allows selection of input phosphor size
  • 2 or 3 size selections
  • 25/17
  • 25/17/12 or 23/15/10
  • Smaller input magnifies output by moving focal
    point away from output
  • Requires more x-rays to maintain brightness

18
IMAGE INTENSIFIER
  • CESIUM IODIDE Input Phosphor
  • ZINC CADMIUM SULFIDE Output phosphor
  • ELECTRON FOCUSING LENS
  • CURRENT ATTRACTS e TO ANODE
  • 25 35 KVP POTIENTIAL ACROSS TUBE
  • Output phosphor contains a thin al plate to
    prevent light returning to the photocathode

19
The anode of the II
  • The anode is about 20 away from these electrons
    so what will help move the Es?
  • 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

20
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21
Image intensifier component
  • Input screen conversion of incident X Rays into
    light photons (CsI)
  • 1 X Ray photon creates ? 3,000 light photons
  • Photocathode conversion of light photons into
    electrons
  • only 10 to 20 of light photons are converted
    into photoelectrons
  • Electrodes focalization of electrons onto the
    output screen
  • electrodes provide the electronic magnification
  • Output screen conversion of accelerated
    electrons into light photons

22
Intensifier Brightness Gain (BG)
  • BG
  • Minification Gain x Flux Gain
  • Minification gain (MG) The ratio of the squares
    of the input and output phosphor diameters. This
    corresponds to concentrating the light into a
    smaller area, thus increasing brightness
  • MG (Input Diameter )2
  • (Output Diameter)2

23
Minification
  • Electrons had to be focused down to fit through
    the hole at the anode Input phosphor is much
    bigger than the anode opening
  • Input phosphors are 10-35 cm in diameter
  • (6, 9 , 12
    inches)
  • Output phosphors are 2.5 to 5 cm (1 in) in
    diameter
  • Most fluoro tubes have the ability to operate in
    2 sizes (just like small and large focal spot
    sizes)
  • Bi focus - MNewer units - tri focus

24
Intensifier Flux Gain
25
FLUX GAIN
  • 1000 light photons at the photocathode
  • from 1 x-ray photon
  • photocathode decreased the of ës so that they
    could fit through the anode
  • Output phosphor
  • 3000 light photons (3 X more than at the input
    phosphor!)
  • This increase is called the flux gain

26
Flux gain
  • The ratio of the number of light photons striking
    the output screen to the ratio of the number of
    x-ray photons striking the input screen is called
    fluxgain

27
Brightness gain
  • The II makes the image brighter because it
    minified it and more light photons.
  • Multiply the flux gain times the minification
    gain.

28
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 - IIMAGE LAG

29
BG MG X FG
  • FLUX GAIN increase of light brightness due to
    the conversion efficiency of the output screen
  • 1 electron 50 light photons is 50 FG
  • Can decrease as II ages
  • Output phosphor almost always 1 inch
  • Zinc cadnium phosphot
  • Flux gain is almost always 50

30
BG MG X FG
  • Brightness gain BG
  • MINIFICATION GAIN X FLUX GAIN
  • (old Patterson B-2 fluoro obsolete)
  • Brightness gain is a measure of the conversion
    factor that is the ratio of the intensity of the
    output phosphor to the input phosphor
  • conversion factor intensity of OP Ø

  • mR/sec

31
Image Intensifier Terms
  • Brightness Gain
  • Ability of II to increase illumination
  • Minification Gain
  • Flux Gain (usually stated rather than calculated)

32
Intensifier Performance
  • Conversion factor is the ratio of output
    phosphor image luminance (candelas/m2) to x-ray
    exposure rate entering the image intensifier
    (mR/second).
  • Very difficult to measure no access to output
    phosphor
  • No absolute performance criteria

33
Intensifier Brightness Gain
  • Flux Gain (FG) Produced by accelerating the
    photoelectrons across a high voltage (gt20 keV),
    thus allowing each electron to produce many more
    light photons in the output phosphor than was
    required to eject them from the photcathode.
  • Summary Combining minification and flux gains

34
Intensifier Brightness Gain
  • Example
  • Input Phosphor Diameter 9
  • Output Phosphor Diameter 1
  • Flux Gain 75 (usually 50)
  • BG FG x MG 75 x (9/1)2 6075
  • Typical values a few thousand to gt10,000 for
    modern image intensifiers

35
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

36
Cesium Iodide (CsI) Phosphor
  • The column shaped
  • Helps to direct the
  • Light with
  • Less blurring

37
Intensifier Format and Modes
Note focal point moves farther from output in mag
mode
38
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39
Units of measurement
  • INPUT PHOSPHOR IS MEASURED IN
    _________________________________
  • OUTPUT PHOSPHOR IS MEASURED IN
  • ______________________________

40
Units of measurement
  • INPUT PHOSPHOR IS MEASURED IN
  • Milliroentgens mR
  • OUTPUT PHOSPHOR IS MEASURED IN
  • CANDELAS (LIGHT)
  • VIEWBOXES ARE MEASURED IN lamberts (light)

41
MAG MODE VS PT DOSE
  • MAG USED TO ENLARGE SMALL STRUCTURE OR TO
    PENETRATE THROUGH LARGER PARTS
  • PATIENT DOSE IS INCREASED IN THE MAG MODE
  • DEPENDANT ON SIZE OF INPUT PHOSPHOR

42
MAG MODE FORMULA
  • IP OLD SIZE
  • IP NEW SIZE mag

43
PT dose in MAG MODE
  • IP OLD SIZE 2
  • IP NEW SIZE 2 ? pt dose

44
Minification gain - again
  • BG MINIFICATION GAIN X FLUX GAIN
  • MINIFICATION GAIN same e at input condensed
    to output phosphor ratio of surface area on
    input screen over surface area of output screen
  • IP SIZE 2
  • OP SIZE 2

45
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

46
Brightness Control
  • Automatic brightness stabilization
  • Automatic adjustments made to exposure factors by
    equipment
  • Automatic gain control
  • Amplifies video signal rather than adjusting
    exposure factors

47
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
  • kVmA variable
  • Pulse width variable (cine and pulsed fluoro)
  • less dose with pulsed vs continous fluoro

48
Fluoroscopic Dose Rates
49
Intensifier Format and Mag Modes
50
Image Quality
  • Contrast
  • Resolution
  • Distortion
  • Quantum mottle

51
Contrast
  • Controlled by amplitude of video signal
  • Affected by
  • Scattered ionizing radiation
  • Penumbral light scatter

52
Resolution
  • Video viewing
  • Limited by 525 line raster pattern of monitor
  • Newer digital monitors 1024 - better resolution

53
Size Distortion
  • Affected by same parameters as static radiography
  • Primarily OID
  • Can be combated by bringing image intensifier as
    close to patient as possible

54
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

55
Image distortion
PINCUSHION EFFECT
56
Quantum Mottle
  • Blotchy, grainy appearance
  • Caused by too little exposure
  • Most commonly remedied by increasing mA

57
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 and transmit 10 onto the
    television camera.

58
Viewing Fluoroscopic Images
59
Recording the Fluoroscopic Image
  • STATIC IMAGES
  • Cassettes
  • 105 mm chip film 12 frames per second
  • Digital fluoroscopy
  • DYNAMIC VIEWING
  • Cine film
  • Videotape

60
TV camera connections
  • several ways to connect the TV camera to the II.
  • fiber optics bundle to allow light off the output
    phosphor to go to the TV camera
  • OLD UNITS - only recording device was???
  • lens coupling device that allows the light from
    the output phosphor to be split by a mirror so
    that a portion is sent to the TV camera and a
    portion is sent to the film camera.

61
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 /105 PHOTOSPOT / VIDEO/
    CINE

62
Recording the Fluoroscopic Image
  • Dynamic systems
  • Cine film systems
  • Videotape recording
  • Static spot filming systems

63
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 1
  • Cassette loaded spot film increases patient dose
  • Photo spot camera will take the image right off
    the output phosphor
  • This requires less patient dose

64
Cassettes
  • Standard size - 9 x 9
  • Stored in lead-lined compartment until ready for
    exposure
  • When exposure is made, mA is raised to
    radiographic level
  • Multiple image formats

65
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66
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

67
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

68
Fluoroscopy mA
  • Low, continuous exposures .05 5 ma
  • (usually ave 1 2 ma)
  • Radiographic Exposure
  • (for cassette spot films)
  • mA increased to 100 200 mA

69
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

70
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

71
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72
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73
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

74
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75
Other Recording
  • From II - Light is split by lenses
  • Beam splitter is a partially reflective mirror.
  • It allows about 80-90 is transmitted to the
    camera tube
  • Remaining light directed to recording systems
    ex Cine

76
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77
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78
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 ?)

79
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

80
OVERFRAMING vs Exact Framing
81
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 - vidicon
  • Inside 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

82
VIDEO/CAMERA TUBE
  • PLUMICON, VIDICON, ORTHOCON, CCDs
  • 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

83
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

84
Type of TV camera
  • VIDICON TV camera most commonly used in
    diagnostic
  • 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
  • ??LOWER PT DOSE than Vidicon but more Quantum
    M.
  • 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

85
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.

86
Vidicon (tube) TV Camera
87
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88
camera tube have a diameter of approximately 1
inch and a length of 6 inches.
89
Vidicon Target Assembly
90
Viewing Systems
  • Video camera charge-coupled device (CCD)
  • Video monitor
  • Digital

91
Video Viewing System
  • Closed circuit television
  • Video camera coupled to output screen and monitor
  • Video cameras
  • Vidicon or Plumbicon tube
  • CCD

92
(No Transcript)
93
Video Field Interlacing
94
TV Monitor
95
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.

96
Different types of scanning
11
1
INTERLACED SCANNING
12
13
2
3
15
14
5
625 lines in 40 ms i.e. 25 frames/s
4
17
16
7
6
19
18
8
9
20
21
10
1
2
3
4
5
6
7
PROGRESSIVE SCANNING
8
9
10
11
12
13
14
15
16
17
18
97
Synchronization (Sync Signals)
98
TV RESOLUTION-Vertical
  • Conventional TV 525 TV lines to represent entire
    image. Example 9 intensifier (9 FOV)
  • 9 229 mm
  • 525 TV lines/229 mm 2.3 lines/mm
  • Need 2 TV lines per test pattern line-pair
  • (2.3 lines/mm) /2 lines/line-pair 1.15 lp/mm
  • Actual resolution less because test pattern bars
    dont 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

99
KELL FACTOR
  • VERTICAL RESOLUTION
  • ABILITY 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

100
TV RESOLUTION-Horizontal
  • Along a TV line, resolution is limited by how
    fast the camera electronic signal and monitors
    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)

101
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

102
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103
Digital Fluoroscopy
  • Use CCD to generate electronic signal
  • Signal is sent to ADC
  • Allows for post processing and electronic storage
    and distribution

104
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105
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

106
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

107
DIGITAL Fluoro System
108
DIGITAL FLUORO
109
ADC
  • ANALOG TO DIGITAL CONVERTER
  • TAKE THE ANALOG ELECTRIC SIGNAL CHANGES IT TO A
    DIGITAL SIGNAL
  • TO MONITOR
  • BETTER RESOLUTION WITH DIGITAL UNITS

110
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111
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112
DSA POSTPROCESSING
113
Fluro Rad Protecion
114
Regulatory Requirements
  • 1. Regarding the operation of fluoroscopy units
  • 2. Regarding personnel protection
  • 3. Regarding patient protection

115
Fluoroscopic Positioning Previewing
  • Radiographers are trained in positioning
  • Unnecessary radiation exposure to patient is
    unethical
  • Fluoroscopic equipment should not be used to
    preview patients position

116
Patient Protection
  • Tabletop exposure rate
  • Maximum 10 R/min
  • Typically 1 3 R/min
  • Some books ave is 4 R/min

117
Patient Protection
  • Minimum source-to-skin distance
  • 12 for mobile equipment
  • 15 for stationary systems
  • Audible alarm at 5 mins.
  • Same rules for collimation

118
Patient Protection
  • Typical exposure rates
  • Cinefluorography
  • 7.2 R/min
  • Cassettes
  • 30 mR/exposure
  • 105 mm film
  • 10 mR/exposure

119
Protection of Radiographer and Radiologist
  • Single step away from the table decreases
    exposure exponentially
  • Bucky slot cover
  • Lead rubber drape
  • Radiologist as shielding

120
Protection of Others
  • Radiographers responsibility to inform others in
    the room to wear lead apron
  • Do not initiate fluoroscopy until all persons
    have complied

121
PUBLIC EXPOSURE
  • 10 OF OCCUPATIONAL
  • NON MEDICAL EXPOSURE
  • .5 RAD OR 500 MRAD
  • UNDER AGE 18 AND STUDENT
  • .1 rem 1 mSv

122
COLLIMATION (X-RAY TUBE)
  • The PATIENTS SKIN SURFACE
  • SHOULD NOT BE CLOSER THAN
  • ___________ CM BELOW THE COLLIMATOR?
  • ____________ INCHES?

15 cm / 6.5 inches
123
Protection
  • Lots to remember in the summer, for right now
  • Tube in never closer to the patient than 15 in
    stationary tubes and 12 with a C arm
  • As II moves away from the patient the tube is
    being brought closer
  • Bucky tray is connected to a lead shield called
    the Bucky slot cover. It must be 0.25 mm Pb
  • There should be a protective apron of at least
    0.25 mm Pb that hangs down from the II
  • Every machine is required to have an audible
    timer that signals 5 minutes of fluoroscopy time
  • Exposure switch must be a dead man type

124
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

125
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

126
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

127
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

128
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

129
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130
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

131
SSD TUBE TO SKIN DISTANCE
  • FIXED UNITS
  • 18 PREFERRED
  • 15 MINIMUM
  • MOBILE UNITS ( C-ARMS)
  • 12 MINIMUM

132
PATIENT PROTECTION
  • LIMIT SIZE OF BEAM
  • BEAM ON TIME
  • DISTANCE OF SOURCE TO SKIN
  • PBL
  • FILTRATION (2.5 mm Al eq) _at_ 70
  • SHEILDING
  • SCREEN/FILM COMBO

133
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134
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

135
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 ?

136
KEEP I.I. CLOSE TO PATIENT
137
Over vs under the table fluoro tubes
138
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

139
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

140
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

141
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

142
RADIATION PROTECTION The 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

143
BUCKY SLOT COVER
  • .25 MM LEAD

144
ISOEXPOSURE CURVES
145
PERSONNEL PROTECTION
  • SCATTER FROM THE PATIENT
  • TABLE TOP, COLLIMATOR, TUBE HOUSING, BUCKY
  • STRAY RADIATION LEAKAGE OR SCATTER RADIATION

146
TOWER CURTAIN
  • .25 MM LEAD EQ

147
PERSONNEL PROTECTION
  • STANDING BEHIND A PROTECTIVE PRIMARY (1/16TH pb)
    BARRIER
  • PRIMARY RADIATION EXPOSURE 99.87 REDUCED
  • PORTABLE BARRIER 99 REDUCTION

148
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)

149
PERSONNEL PROTECTION MONITORING
  • FILM BADGE
  • TLD
  • POSL
  • POCKET DOSIMETER
  • RING BADGE

150
PERSONNEL PROTECTION MONITORING
  • DOSE LIMITS
  • WHOLE BODY
  • EYES
  • EXTREMITIES (BELOW ELBOW/KNEES)

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152
Report at least every quarter Preserved for a
minimum of 3 years
153
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

154
LICENSE RENEWAL
  • WITHIN 30 DAYS OF EXPRIATION
  • NOTIFICATION OF CHANGE OF ADDRESS

155
HIGH RADIAITON AREA
  • 100 mRem ( 0.1 rem / (1 msV)
  • _at_ 30 cm from the source of radiaton
  • RADIAITON AREA
  • RHB 5 mRem ( 0.005 rem / (.05 msV)
  • _at_ 30 cm from the source of radiation
  • PUBLIC 2 mrem per week (STAT)

156
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

157
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

158
RHB RULES RHB RP PG62
  • ALL XRAYS MUST BE ORDERED BY A PHYSICIAN
  • VERBAL OR WRITTEN PRESCRIPTION
  • See Section C Technologist Restrictions

159
Declared Pregnant Worker
  • Must declare pregnancy 2 badges provided
  • 1 worn at collar (Mothers 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

160
DOSE
  • CINE - 2mR per frame (60f/sec)
  • 400 mr per look

161
FLUORO RAD PROTECTION REVIEW QUESTIONS
162
  • If at ½ foot from the radiation source the
    intensity of exposure is 240 mR per hour and you
    remain at this location for 10 minutes, you then
    moved 2 feet away from the radiation source and
    remained there for 20 minutes? What is your
    total exposure?

163
  • If at ½ foot from the radiation source the
    intensity of exposure is 240 mR per hour and you
    remain at this location for 10 minutes, you then
    moved 2 feet away from the radiation source and
    remained there for 20 minutes? What is your
    total exposure?
  • 45 mR

164
  • The greatest contribution of unnecessary
    radiation exposure to the patient comes
  • from the x-ray operators failure to

165
  • The greatest contribution of unnecessary
    radiation exposure to the patient comes
  • from the x-ray operators failure to
  • COLLIMATE

166
  • All of the following must be posted in areas
    where x-ray production machines are utilized
    except
  • each x-ray supervisor and operator permit
  • each certified radiologic technologist
    certificate and technologist fluoroscopy permit
  • Radiologic Health Department Form RH-2364,
    Notice to Employee
  • each physicians license for the healing arts

167
  • All of the following must be posted in areas
    where x-ray production machines are utilized
    except
  • each physicians license for the healing arts

168
  • During a 2 minute
  • (fluoroscopy exposure time)
  • routine upper GI series examination
  • a typical x-ray exposure to the patient is

169
  • During a 2 minute
  • (fluoroscopy exposure time)
  • routine upper GI series examination
  • a typical x-ray exposure to the patient is
  • 5 8 R (ave 4 R/ min)

170
  • For a fluoroscopic system equipped with and
    automatic brightness control
  • (automatic exposure control) mechanism and where
    the x-ray tube is fixed
  • below the table, moving the image intensifier way
    from the patient will

171
  • For a fluoroscopic system equipped with and
    automatic brightness control
  • (automatic exposure control) mechanism and where
    the x-ray tube is fixed
  • below the table, moving the image intensifier way
    from the patient will
  • INCREASE EXPOSURE

172
  • If at one foot from the radiation source
  • the intensity of exposure is
  • 240(mR) per hour
  • And you remain at this location for
  • 10 minutes
  • you will receive and exposure of ______?
  • What dose if you remained there for 20 minutes?

173
  • If at one foot from the radiation source
  • theintensity of exposure is
  • 240(mR) per hour
  • And you remain at this location for
  • 10 minutes
  • you will receive and exposure of ______?
  • What dose if you remained there for 20 minutes?
  • 40(mR)
  • 80 mR

174
  • When the target to panel (tube to patient)
    distance is increased from 12 to 18 inches the
    ESE to patient is approximately
  • a. Increased by 45
  • c. Decreased by 100
  • b. Increased by 25
  • d. Decreased by 45

175
  • When the target to panel (tube to patient)
    distance is increased from 12 to 18 inches the
    ESE to patient is approximately
  • Decreased by 45

176
  • At 1 foot from a source the output intensity is
    300 mR/hr and you were there for 20 minutes.
  • What is the intensity total if you moved 2 feet
    away and remained for an additional 40 minutes?
  • __________________ ?

177
  • At 1 foot from a source the output intensity is
    300 mR/hr and you were there for 20 minutes.
  • What is the intensity total if you moved 2 feet
    away and remained for an additional 40 minutes?
  • 150 mr

178
  • Fluoro equipment made after 1974 with AEC shall
    not produce an exposure rate to the patient in
    excess of
  • a. 1 R/ min c. 5 R/min
  • b. 10 R/min d. 20 R/min

179
  • Fluoro equipment made after 1974 with AEC shall
    not produce an exposure rate to the patient in
    excess of
  • 10 R/min - regular mode
  • 20 R/min - boost (mag) mode

180
  • Kilovolt peak (kvp) the intensity of the x-ray
    beam at table top should not exceed how many
    roentgens per minute for each milliampere (ma) of
    current?
  • 0.2 roentgens per minute
  • 1.0 roentgens per minute
  • 2.2 roentgens per minute
  • 5.0 roentgens per minute

181
  • Kilovolt peak (kvp) the intensity of the x-ray
    beam at table top should not exceed how many
    roentgens per minute for each milliampere (ma) of
    current?
  • 2.2 roentgens per minute

182
  • The NCRP states that the risk (to the
    embryo/fetus) is considered to be negligible at 5
    rads or less when compared to the other risks of
    pregnancy ,
  • and the risk of malformation is significantly
    increased above control levels only at doses
    above how many rads
  • a. 7 b.10 c.15 d. 25

183
  • The NCRP states that the risk (to the
    embryo/fetus) is considered to be negligible at 5
    rads or less when compared to the other risks of
    pregnancy ,and the risk of malformation is
    significantly increased above control levels only
    at doses above how many rads
  • 15 rads RHB (Stat 10 -20
  • 50 rads spontaneous abortion

184
  • A high radiation area is any area , accessible
    to individuals, in which there exists radiation
    at such levels that an individual could receive
    in any one hour a dose to the whole body in
    excess of how many millirems ?
  • a.5 b. 10 c. 50 d. 100

185
  • A high radiation area is any area , accessible
    to individuals, in which there exists radiation
    at such levels that an individual could receive
    in any one hour a dose to the whole body in
    excess of how many millirems ?
  • 100

186
  • The exposure rate to a tech at 4 feet from the
    source is 240 m R/hr. What distance would be
    necessary to reduced the rate below 60 mR/hr?
  • A. 1 foot
  • B. 6 feet
  • C. 2 feet
  • D. 9 feet

187
  • The exposure rate to a tech at 4 feet from the
    source is 240 m R/hr. What distance would be
    necessary to reduced the rate below 60 mR/hr?
  • 9 feet

188
  • If 85 kvp, 400ma 0.12s 150mR - what is the
    mr/mas?
  • A. 0.32
  • B. 3.1
  • C. 33.1
  • D. 17.6

189
  • If 85 kvp, 400ma 0.12s 150mR - what is the
    mr/mas?
  • 3.125

190
  • Each time an x-ray beam scatters, its intensity
    at 1 meter from the scattering object is what
    fraction of its original intensity?
  • A. 1/10
  • B. 1/100
  • C. 1/500
  • D. 1/1000

191
  • Each time an x-ray beam scatters, its intensity
    at 1 meter from the scattering object is what
    fraction of its original intensity?
  • 1/1000 or .1

192
  • Which of the following gives the least patient
    exposure?
  • a. mirror optical system
  • b. vidicon TV camera
  • c plumicon TV camera
  • d. image orthicon

193
  • Which of the following gives the least patient
    exposure?
  • PLUMBICON TV camera

194
  • During a CINE exam in which 35 mm film and a
    frame rate of 30 frames per second are utilized,
    what is the approximate skin exposure in
    roentgens/minutes?
  • a. 1 (given 2mr/frame)
  • b. 2 5
  • c. 5 10
  • d. over 10

195
  • During a CINE exam in which 35 mm film and a
    frame rate of 30 frames per second are utilized,
    what is the approximate skin exposure in
    roentgens/minute?
  • (given 2mr/frame)
  • 2 5 R
  • 30f x 60 sec 1800 f x 2 mr 3600 mr 3.6R

196
FLUOROSCOPY REVIEW RT 255
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