Fluoroscopy Review Notes From CDPH RHB Syllabus

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Fluoroscopy Review NotesFrom CDPH RHB Syllabus

• Rad Tech 244 - 2013

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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

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• 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.

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• 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.

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Notes Chapter 2Factors 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

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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

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Factors indirectly influencing exposure

• Room illumination
• Image receptor quality
• Absorption of the table top

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mA

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

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kVp

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

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collimation

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

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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.

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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
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filtration

• If the tube is operated above 125 kVp, 3 mm Al eq
  is required.
• Filtration reduces patient dose

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Source to table toptarget to panel distance

• Cannot be less than 12 and should be 18
• Mobiles are required to be at least 12
• Fixed units, 15

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Patient to II distance

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

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• Tabletop
• Less than 1 mm Al eq at 100 kVp

• Exposure switch
• Dead man type

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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

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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

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

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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

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II Facts

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

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Image Quality Issues

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

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

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Closed Circuit TV Systems

• Camera
• MC is the vidicon
• Camera control unit
• Video amplifier
• Monitor
• CRT, etc.

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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

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• 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

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Accessories

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

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Factors affecting an Increase in Scatter

• High kVp
• Large field size
• Thick body part

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Advantages of 3 phase and medium/high frequency
generators

• Relatively high mA
• Higher effective kVp
• Near constant potential
• Less ripple

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Notes for Chapter 3

• Fluoro Image Production
• Fluoro units have 2 basic components
• X-ray tube
• Image intensifier

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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

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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

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• 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

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

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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

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Image Intensifier Magnification Modes
Same area
Output phosphor
Input Phosphor
9 inch field
6.5 inch field
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RELATIVE PATIENT ENTRANCE DOSE RATE FOR SOME UNITS
IMAGE INTENSIFIER
Active Field-of-View (FOV)
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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.

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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.

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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

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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

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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

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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

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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

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Brightness Sensing

• II photocathode current
• Television camera signal sensing
• Lens coupled phototube sensing

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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

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Closed Circuit TV Systems

• Camera
• Camera control unit
• Power supply and video amplifier
• Monitor

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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

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Photoconductive camera tube
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Schematic structure of a charged couple device
(CCD)
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Monitor

• 525 lines 30 times per second
• Combined with the video camera improves image
  contrast

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TV Image Quality

• Horizontal resolution
• Vertical resolution
• Contrast
• Brightness
• Lag

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• 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

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

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Dynamic Image Recording

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

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• 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

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• 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

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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

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• 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

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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

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Pulsed Fluoroscopy

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

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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

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Notes from Chapter 4Conducting the Fluoro Exam

• Operator dose is directly proportional to patient
  dose
• Image brightness is directly proportional to dose
  rate at input phosphor

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Technical factors which directly influence dose
rate at the table top

• mA
• kVp
• Collimation
• Filtration
• Exposure time
• Target panel distance

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Technical factors which indirectly influence dose
by affecting technical factors

• Room lighting
• Image receptor quality
• tabletop

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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)

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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

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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

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TPD

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

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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

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Gonadal Shields

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

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Notes from Chapter 5Basic 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

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• 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

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

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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
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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
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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
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Mobile Concerns

• Audible indicator
• Cumulative timer visible on the monitor
• Video storage
• Last frame hold
• Longest possible TPD

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Notes for Chapter 6Pediatric Fluoroscopy

• Motion
• Sedation
• Mechanical devices
• Personnel and Parental Protection
• Everyone in the room needs lead
• Gonadal shielding
• Artifacts

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

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Notes for Chapter 7Mobile 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

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• 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

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Notes for Chapter 8Responsibilities 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

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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

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Personnel Protection

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

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Protection Devices
SCREEN AND GOGGLES
CURTAIN
THYROID
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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

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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

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Notes on Chapter 9Supervision 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

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

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Notes on Chapter 10Health 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

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• 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

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Notes on Chapter 11Biological 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

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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

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Dose relationship curves
Non-threshold linear
Threshold Non-linear
Regulations are based on non-threshold linear
curves
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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

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Cell Sensitivity

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

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Short Term Effects

• 25 rads or less demonstrate no effects

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Long Term Effects

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

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Carcinogenic Effects

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

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Radiation Induced Cancers

• Female breast
• Thyroid
• Hemopoitic tissue
• Lungs
• GI tract
• Bones

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Embryological Effects

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

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Notes on Chapter 12Personnel 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

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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

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Notes on Chapter 13Personnel Monitoring

• Record exposure
• Measure accumulated exposure
• Indicate type of exposure
• Provide a record of exposure

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Types

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

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Maximum Permissible DoseFor 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

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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
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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

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