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Fluoroscopy Notes

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Title: Fluoroscopy Notes


1
Fluoroscopy Notes
  • Rad Tech 290

2
Fluoroscopy Notes Ch 1
  • Approximately 5 of the US population has a
    fluoro procedure each year
  • The average number of fluoro exams per person is
    1.3
  • The average number of spot films is 4.6

3
  • The MC exam is a GI tract at 53
  • A 2 minute UGI exam can produce an exposure
    ranging from 5-15 rads, comparatively a KUB is
    between 100-500 mrads.
  • Fluoro is defined as a rad exam utilizing
    fluorescence for the observation of the transient
    image.

4
  • Fluoro was first used as a dynamic procedure.
    Second as a means of positioning for spot films.
  • Medical exposure accounts for about 20 of the
    total radiation people receive.
  • Even though the percentage is small, for medical
    exposure, it is the only exposure that is
    controllable.
  • FLUOROSCOPY TO POSITION PATIENTS IS PROHIBITED.

5
Notes Chapter 2 Factors Directly Affect Exposure
  • mA
  • kVp
  • Collimation
  • Filtration
  • Exposure time
  • Total fluoro time
  • Target to panel distance (TPD)
  • Patient to II distance
  • Sensitivity of the image receptor
  • Essentially speed RSV

6
The following will reduce exposure
  • Collimating
  • Last frame hold
  • Shortest possible patient to II distance
  • Highest possible kVp
  • Pulsed fluoroscopy
  • Using the largest II mode with collimation

7
Factors indirectly influencing exposure
  • Room illumination
  • Image receptor quality
  • Absorption of the table top

8
mA
  • 0.5 5 mA
  • Usually 1 3 mA
  • Spot films
  • 100 mA or higher
  • Output and dose are directly proportional to mA

9
kVp
  • Maximum photon energy
  • Beam quality
  • Penetrability of the beam
  • Tube potential

10
collimation
  • Required by law
  • Image quality improves as the beam is collimated

11
Collimation
  • Collimate tightly to the area of interest.
  • Reduces the patients total entrance skin
    exposure.
  • Improves image contrast.
  • Scatter radiation to the operator will also
    decrease.

12
Factor affecting staff doses
FIELD SIZE DEPENDENCE
Scattered dose rate is higher when field size
increases
11x11 cm
17x17 cm
17x17 cm
100 kV
0.8 mGy/h
1.3 mGy/h
1 mA
0.6 mGy/h
1.1 mGy/h
0.3 mGy/h
0.7 mGy/h
1m patient distance
Patient thickness 18 cm
13
filtration
  • If the tube is operated above 125 kVp, 3 mm Al eq
    is required.
  • Filtration reduces patient dose

14
Source to table top target to panel distance
  • Cannot be less than 12 and should be 18
  • Mobiles are required to be at least 12
  • Fixed units, 15

15
Patient to II distance
  • The closer the II, the lower the dose
  • This is more pronounced with fixed units.
  • Decreases the SID

16
  • Tabletop
  • Less than 1 mm Al eq at 100 kVp
  • Exposure switch
  • Dead man type

17
Primary protective barrier
  • The II is the primary barrier and must have 2 mm
    Pb eq for systems operating above 125 kVp
  • The II has to be in place for the tube to energize

18
Protective Actions
  • Bucky Slot Cover
  • Automatically covered, 0.25 mm Pb eq
  • Protective curtains
  • 0.25 mm Pb eq
  • Not required on c-arms
  • Scatter at 1 foot can reach 500 mrad/hr

19
  • Allowable exposure rates
  • Cannot exceed 5 rad/minutes
  • Unless, ABC or image recording
  • Cumulative timer
  • Cannot exceed 5 minutes
  • Illumination

20
II Considerations
  • Purpose
  • The basic purpose of the II is to make the fluoro
    image brighter
  • When the image is brighter it is easier to
    visualize structures
  • Brightness Gain
  • Minification gain multiplied by electronic (flux)
    gain

21
II Facts
  • Input phosphor, cesium iodide
  • Photcathode, danium antimony
  • Output phosphor, zinc cadnium sulfide

22
Image Quality Issues
  • Quantum Mottle
  • Caused by too few photons
  • Contrast
  • Subject
  • Detector
  • Image
  • Resolution

23
Effect of X ray Beam Penetration on Contrast,
Body Penetration, and Dose
24
Dose vs. Noise
2 µR per frame
25
  • Distortion
  • Size, shape, pincushion
  • Lag
  • Vignetting
  • Less bright at the edges than center of image
  • Magnification tubes, Multi-mode
  • Variable FoV

26
Closed Circuit TV Systems
  • Camera
  • MC is the vidicon
  • Camera control unit
  • Video amplifier
  • Monitor
  • CRT, etc.

27
Cinefluoroscopy
  • Synchronization
  • Record with the x-ray pulses
  • Framing frequency
  • Division of 60
  • The higher the rate the higher the dose
  • F-number
  • Video disk recording (electronic radiography)
  • Exposure ends when image is formed
  • Basically fluoro phototiming
  • 95 dose reduction

28
  • Video tape
  • Instant playback and no additional dose
  • Spot films
  • Conventional cassettes
  • Photospot cameras
  • ½ to 1/3 dose of convent. Cass.
  • Lower image quality

29
Accessories
  • Gonadal shields
  • Required when possible
  • Grids
  • Fluoro uses low ratio grids
  • Cassettes
  • Cine film
  • Per frame basis 10 x the dose than fluoro

30
Factors affecting an Increase in Scatter
  • High kVp
  • Large field size
  • Thick body part

31
Advantages of 3 phase and medium/high frequency
generators
  • Relatively high mA
  • Higher effective kVp
  • Near constant potential
  • Less ripple

32
Notes for Chapter 3
  • Fluoro Image Production
  • Fluoro units have 2 basic components
  • X-ray tube
  • Image intensifier

33
Fluoro X-ray Tube
  • Regular rotating anode x-ray tube
  • Runs at a lower mA
  • Less than 5 mA
  • Small focal spot
  • Possible because of the low mA

34
II
  • The primary purpose is to increase the brightness
    of the fluoro image
  • Components
  • Glass envelope that provides a vacuum
  • Input layer
  • Converts x-ray photons to electrons
  • Electronic (electostatic) lens
  • Output layer

35
  • Input layer
  • Converts x-ray photons to light photons
  • Light photons then strike the photocathode and
    convert into electrons
  • Electrons are then accelerated across the II
  • Electrons strike the output phosphor and are
    converted back into light photons

36
The image intensifier (I.I.)
I.I. Input Screen
Electrode E1
Electrode E2
Electrode E3
Electrons Path
I.I.Output Screen
Photocathode

37
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

38
Image Intensifier Magnification Modes
Same area
Output phosphor
Input Phosphor
9 inch field
6.5 inch field
39
RELATIVE PATIENT ENTRANCE DOSE RATE FOR SOME UNITS
IMAGE INTENSIFIER
Active Field-of-View (FOV)
40
Brightness Gain
  • BG is the product of minification gain and
    flux(electronic) gain
  • Minification Gain
  • Input phosphor dia.2/output phosphor dia2
  • Making the image smaller will make it brighter.
  • The same number of photons are contained in a
    smaller area
  • In most IIs the output phosphor is 1 inch.

41
Flux Gain
  • Caused by the conversion efficiency of the output
    phosphor and the acceleration of the electrons
    across the II
  • As the electrons accelerate they gain kinetic
    energy
  • Flux gain is usually between 50 and 150.

42
Measuring Brightness Gain
  • The actual measurement is done by calculating the
    conversion factor
  • Intensity of output phosphor (candelas)/mrads/sec
  • Brightness gain will deteriorate 10 annually.
  • This will ultimately decrease image contrast

43
Beam Splitter Mirror
  • 10 of the output light goes to the vidicon
    (video camera) the remainder goes to the
    photospot device.
  • NOTE not all units have a beam splitter

44
Vignetting and Pincushion Distortion
  • Pincushion
  • The loss of shape at the edges of the fluoro
    image
  • Vignetting
  • Loss of brightness at the edge of the image

45
Veiling Glare
  • Occurs when the light from the output phosphor
    reflects back into the II.
  • Remember, the photocathode is stimulated by
    light, so light reflecting from the output
    phosphor would also trigger electron production.
  • Decreased contrast results

46
Automatic Brightness Stabilization
(ABS) Automatic Brightness Control (ABC)
  • Keeps light output of the II constant.
  • Brightness of the image varies with changes to
    kVp and mA.
  • Increase mA increase brightness direct
    relationship
  • Increase kVp 10 double brightness

47
Brightness Sensing
  • II photocathode current
  • Television camera signal sensing
  • Lens coupled phototube sensing

48
Types of ABS
  • Variable mA, preset kVp
  • Set the kVp and the unit adjusts mA
  • Variable mA with kVp following
  • If the mA range is exceeded the unit will
    automatically adjust the kVp to compensate
  • Variable kVp, preset mA
  • Set the mA and the unit adjusts kVp
  • Variable kVp, variable mA

49
Closed Circuit TV Systems
  • Camera
  • Camera control unit
  • Power supply and video amplifier
  • Monitor

50
Cameras
  • Vidicon
  • MC, inexpensive, lag, 525 raster lines
  • Plumbicon
  • Cardiac cath labs
  • Fixed gain (better contrast) and low lag
  • Increased quantum mottle
  • Image orthicon
  • Not widely used
  • CCD
  • Solid state semiconductor
  • Small, low power consumption, low price, long life

51
Photoconductive camera tube
52
Schematic structure of a charged couple device
(CCD)
53
Monitor
  • 525 lines 30 times per second
  • Combined with the video camera improves image
    contrast

54
TV Image Quality
  • Horizontal resolution
  • Vertical resolution
  • Contrast
  • Brightness
  • Lag

55
  • Horizontal resolution
  • Bandwidth or bandpass
  • Increase frequency bandwidth increase horizontal
    resolution
  • Vertical resolution
  • Determined by number of scan lines
  • Kell factor
  • Ratio of vertical resolution and scan lines

56
  • Contrast
  • Brightness
  • Adjust contrast first and brightness after
  • Lag
  • Occurs when the II is moved rapidly.

57
Dynamic Image Recording
  • Video Tape
  • 2 advantages
  • Instant replay
  • No additional patient exposure
  • Disadvantages
  • Poor image quality, fixed frame rate,

58
  • Cinefluoroscopy
  • 16 or 35 mm (MC high patient dose, better image)
  • Synchronization
  • Camera shutters open at the same rate as x-ray
    pulses
  • Framing rate
  • F-number
  • The lower the number the more light hitting the
    camera the lower the patient dose however, more
    distortion at the edges

59
  • Framing
  • Underframing should be avoided
  • Exact framing, diameter of the II fits in the
    shortest dimension of the film
  • Overframing, diameter of the II fits the largest
    dimension of the film. Part of the image is lost
  • Total overframing, diameter of the II is equal to
    the diagonal of the film

60
Static Image Recording
  • Video disk
  • Last image freeze (hold) (sticky fluoroscopy)
  • Electronic radiography, similar to AEC x-ray only
    until image is made.
  • Decrease dose up to 95
  • 1 to 30 frames per second
  • Spot film
  • Conventional cassettes

61
  • Spot film
  • Photospot
  • Image is taken from the II output phosphor
  • Dose 20 50 X higher per frame than fluoro
    because of higher mA
  • Currently, 70 mm roll, 105 roll, 100 mm chip
  • 105 mm roll ½ the dose of cassette spots
  • Cassette spots
  • Slower frame rate
  • Higher dose and better spatial resolution

62
Digital Fluoroscopy
  • Digital image is obtained from the output
    phosphor.
  • A vidicon then a digital image processor
  • Or, digital video camera
  • Digital photospot
  • Instant playback, possible image enlargement

63
Pulsed Fluoroscopy
  • Variable frame rates are possible with a
    corresponding decrease in patient dose

64
High level (boost) fluoroscopy
  • Higher tube currents than normal
  • 10-20 mA usual 40 mA potentially
  • Increase patient dose 2-10 times reg. Fluoro
  • 10-50 rads per minute
  • Limited to 20 rad/minute unless recording the
    image
  • Key points
  • Special activation required, audible signal, dose
    rate limited to 20 rad.minute

65
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66
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67
Notes from Chapter 4 Conducting the Fluoro Exam
  • Operator dose is directly proportional to patient
    dose
  • Image brightness is directly proportional to dose
    rate at input phosphor

68
Technical factors which directly influence dose
rate at the table top
  • mA
  • kVp
  • Collimation
  • Filtration
  • Exposure time
  • Target panel distance

69
Technical factors which indirectly influence dose
by affecting technical factors
  • Room lighting
  • Image receptor quality
  • tabletop

70
Collimation
  • A border needs to be visible when the II is 14
    inches above the tabletop and the collimator is
    fully opened
  • With an automatic collimator, a border should
    always be visible
  • Image is not brighter with a less collimation
    (bigger field size)

71
Filtration
  • Total filtration
  • 2.5 mm Al eq lt 125 kVp
  • 3.0 mm Al eq at 125 kVp and above
  • Total filtration includes inherent and added
  • Exposure rate should be less than 2.2 rads/min at
    80 kVp
  • HVL

72
Allowable exposure rates
  • Limited to 5 rads per minute
  • If the unit has ABC/ABS then 10 rads/minute is
    allowed
  • However, if the unit has boost then the limit
    is 5rads/minute
  • ABC/ABS units have to be checked by a physicist
    annually
  • Also have to have weekly fluoro checks of mA and
    kVp
  • No ABS 3 year check by physicist

73
TPD
  • TPD increases from 12 to 18 inches
  • Pt. Dose decreases by 30
  • II as close as possible to the patient

74
Room Lighting
  • Affects visual acuity
  • Photopic acuity is 10 X better than scotopic
    acuity
  • Day versus night vision
  • Normal viewing distance is 12 15 inches
  • Image recognition in 0.2 seconds

75
Gonadal Shields
  • 0.5 mm Pb eq
  • 97 effective at 100 kVp and 3 mm Al filtration

76
Notes from Chapter 5 Basic Operational Procedures
  • Minimize exposure time by utilizing short looks
  • Use the cumulative timer
  • Use the highest applicable kVp
  • Collimate
  • Use mag and boost only when necessary
  • Use last image hold

77
  • Use a photospot instead of cassettes
  • Use video tape
  • Use II with good contrast
  • Monitor the TV monitor for brightness and
    contrast
  • Minimize the pt. II distance
  • Position the II prior to exposure

78
  • Prevent pt. Motion with instructions
  • Use gonadal shielding when possible
  • Use compression devices

79
Factor affecting staff doses
Scattered dose rate is higher near the area into
which the X-ray beam enters the patient
ANGLE DEPENDENCE
100 kV
0.9 mGy/h
1 mA
0.6 mGy/h
11x11 cm
0.3 mGy/h
1m patient distance
patient thickness 18 cm
80
Factor affecting staff doses
DISTANCE VARIATION
mGy/h at 1m
mGy/h at 0.5m
Scattered dose rate is lower when distance to the
patient increases
100 kV
1 mA
11x11 cm
81
Factor affecting staff doses
Tube undercouch position reduces, in general,
high dose rates to the specialists eye lens
X-Ray tube
mGy/h
100 kV
2.2 (100)
1 m
2.0 (91)
20x20 cm
1.3 (59)
mGy/h
1 Gy/h
(17mGy/min)
1.2 (55)
1.2 (55)
1.2 (55)
1 Gy/h
1m patient distance
(17 mGy/min)
1.3 (59)
20x20 cm
2.2 (100)
100 kV
1m patient distance
1 m
X-Ray tube
82
Mobile Concerns
  • Audible indicator
  • Cumulative timer visible on the monitor
  • Video storage
  • Last frame hold
  • Longest possible TPD

83
Notes for Chapter 6 Pediatric Fluoroscopy
  • Motion
  • Sedation
  • Mechanical devices
  • Personnel and Parental Protection
  • Everyone in the room needs lead
  • Gonadal shielding
  • Artifacts

84
  • ABS/ABC
  • Watch putting the II directly over large
    concentrations of contrast
  • Distance
  • Collimation
  • Photospots instead of cassette spots if possible

85
Notes for Chapter 7 Mobile Fluoroscopic Equipment
  • Primary beam is intercepted by the II
  • If the II is used routinely in a single location
    it needs to have secondary shielding
  • SSD has to be at least 12 inches
  • Must have an II
  • Collimation has to be used or unit will not
    energize
  • Unit cannot energize unless the II is in the
    primary beam

86
  • Maximum dose rate of 5 rads/minute
  • Personnel monitoring in required for all persons
    operating fluoro equipment
  • Protective aprons are required if exposed to more
    than 5mrads/hour
  • Boost mode should only be used after areas of
    interest have been localized

87
Notes for Chapter 8 Responsibilities of X-ray
Supervisor
  • Chief Radiologist or designees are responsible
  • Licentiates who can use and supervise fluoro
  • Radiology supervisor and Operator
  • Fluoro supervisor and Operator
  • Techs with Fluoro permits can only use fluoro
    when supervised by above

88
Specific requirements
  • Establish a fluoro procedures manual
  • Annual review of manual
  • Assure that techs dont practice medicine
  • Observe tech performance
  • Assure techs are offered training
  • Assure equipment monitoring is adhered to

89
Personnel Protection
  • Operator is adequately protected from scatter
  • Individuals in the room need to wear aprons and
    film badges
  • Use protective devices as applicable

90
Protection Devices
SCREEN AND GOGGLES
CURTAIN
THYROID
91
Restrictions
  • Techs can only use fluoro equip. under the
    supervision of a supervisor operator
  • Techs cannot interpret films
  • Techs cannot use a title implying the right to
    practice medicine

92
Notification Requirements
  • Immediate notification (prompt phone call and
    timely letter)
  • Total dose 25 rems
  • Eye dose 75 rems
  • Skin or extremity dose of 250 rems
  • 24 hour notification ( call within 24 hours and a
    letter follow-up)
  • Total dose 5 rems
  • Eye dose 15 rems
  • Skin or extremity 50 rems

93
Notes on Chapter 9 Supervision of Techs w/Fluoro
permits
  • Clear the room of unnecessary personnel
  • Collimate
  • Use shields
  • Use correct technical factors
  • Position the patient correctly
  • Avoid patient motion

94
  • Direct supervision
  • Use equipment only as trained
  • Indirect supervision
  • Spot filming and video taping

95
Notes on Chapter 10 Health Effects of Low Level
Radiation dose
  • Somatic dose indicators
  • Injuries to superficial tissue
  • Induction of cancer
  • Cataracts, fertility issues, life-span shortening
  • Injuries to developing fetus
  • Based on dose at specific locations or points

96
  • High marrow dose exams
  • BE, UGI, abdominal angio
  • Genetic dose indicators
  • 50 rads temp male sterility
  • 30 rads temp female sterility
  • Genetically significiant dose
  • Number of future kids
  • X-ray exam rate
  • Mean gonadal dose/exam

97
Notes on Chapter 11 Biological Effects and
Significance of Dose
  • Effects appear to follow a linear non-threshold
    dose curve
  • Dose rate to tissue
  • Total dose
  • Type of cell exposed

98
Radiobiological injury
  • Cellular amplification
  • Gross cellular effects
  • MC effect is the cessation of cell division
  • Latent Period
  • Short term, weeks or less
  • Immediate or early effects
  • Long term, years or longer
  • Delayed or late effects

99
Dose relationship curves
Non-threshold linear
Threshold Non-linear
Regulations are based on non-threshold linear
curves
100
Variations in Cell Sensitivity
  • Bergonie and Tribondeau
  • Number of undifferentiated cells
  • Degree of mitotic activity
  • Duration of active proliferation
  • Radiation induced mitotic delay is usually
    reversable

101
Cell Sensitivity
  • Lymphocytes or white blood cells
  • RBCs
  • Epithelial
  • Endothelial
  • Connective tissue cells
  • Bone
  • Nerve
  • Brain
  • Muscle

102
Short Term Effects
  • 25 rads or less demonstrate no effects

103
Long Term Effects
  • No specific effect associated with radiation
    exposure
  • Somatic damage
  • Increased incidence of cancer
  • Embryological effects
  • Cataracts
  • Life span shortening
  • Genetic mutations

104
Carcinogenic Effects
  • Human evidence
  • Early radiologists and dentists
  • Radium dial painters
  • Uranium miners
  • Survivors of Hiroshima and Nagasaki

105
Radiation Induced Cancers
  • Female breast
  • Thyroid
  • Hemopoitic tissue
  • Lungs
  • GI tract
  • Bones

106
Embryological Effects
  • As little as 10 rads demonstrates effects in
    animal models
  • 50 rads can cause spontaneous abortion

107
Notes on Chapter 12 Personnel Radiation Protection
  • ALARA
  • Basis for radiation protection requirements
  • Stochastic effects
  • Probability of an event occurring, ie cancer
  • Non-stochastic effects (deterministic)
  • Severity of the effects varies with exposure

108
Operator Exposure
  • Distance
  • Apparel
  • Aprons, 0.25 mm Pb 97 effective
  • 0.5 mm Pb, 99.9 effective
  • Should be placed on hangers when not in use
  • Aprons cover 80 of the bone marrow

109
Notes on Chapter 13 Personnel Monitoring
  • Record exposure
  • Measure accumulated exposure
  • Indicate type of exposure
  • Provide a record of exposure

110
Types
  • Film badge
  • 10 mrad to 700 rads
  • /- 25 accuracy
  • TLD
  • Lithium fluoride
  • /- 9, cannot be reread
  • Others
  • Pocket dosimeter
  • Audible device

111
Maximum Permissible Dose For adults over 18 y/o
  • Whole body - head, trunk, arms above the elbow,
    and legs above the knee
  • 5 Rem
  • Skin and extremities
  • 50 rem
  • Lens
  • 15 Rem
  • Occupational dose for people under 18 y/o 10 of
    adult dose

112
Occupational Exposure Limit
Whole Body 5rem/year Extremities
50rem/year Eye 15rem/year Pregnant workers
0.5rem/gestation period
General public Limited to 0.1 rem/year
(Addition to the background radiation) 0.002 Rem
(2 mrem) per hour
113
Who must be monitored?
  • Persons in high radiation area
  • 0.1 Rem per hour at 30 cm
  • Fluoro rooms
  • Persons operating mobile x-ray equipment
  • Radiation Area
  • 0.005 Rem per hour at 30 cm

114
Typical Exposures
5000
4000
mrem/yr
3000
2000
1000
0
X-Ray Tech
Pain Mgnt.
MPD
Cardio.
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