Transcript Fluoroscopy - Central Georgia Technical College

CVT 102
 Time
 Distance
 Shielding
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Establish standard protocols (including limits
on fluoroscopic exposure time)
Know dose rates of equipment
Assess procedure protocol for potential
radiation injury
Modify procedure to limit cumulative
radiation dose
Medical physicist should help implement
principles
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Pulsed fluoroscopy
Low tube current
◦ Less radiation, less exposure
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Higher kVp
–Higher voltage causes radiation to go
through patient; less absorption; less skin
dose
–Balance contrast and distance
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Distance
◦ Keep image intensifier as close to patient as
possible
◦ Increase distance from x-ray tube to patient
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Field of view
◦ Collimate to reduce field of view to region of
interest
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Limit use of magnification techniques
◦ Magnification increases patient dose
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Last image hold
◦ Displays last image captured on monitor
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Beam on-time
◦ Intermittent fluoroscopy
◦ 5 minute reset timer
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Rotate fluoroscope around a center (do
obliques and laterals)
Keep other body parts (arms, breasts) out of
the x-ray field
Maintain logs to track trends in exposure and
analyze problems
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Inverse square law
◦ The exposure is inversely proportional to the
square of the distance from the source of radiation
(scattered radiation from the patient).
◦ To minimize exposure, stand as far away from the
patient as practical
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Do not put any part of your body in the
primary beam
Distance is the most important method of
protection
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Reduce the time you are exposed to radiation
◦ Fluoroscopist should use intermittent fluoroscopy
◦ Minimize beam-on time
 5 minute audible timer
◦ High dose fluoroscopy requires audible signal while
on
◦ Use last image hold
◦ Use pulsed technique
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Lead aprons (.5mm Pb equivalent)
Thyroid collars
Lead gloves
Leaded glasses
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Dose limits
◦ Whole body – 5,000 mrem/year (50 mSv)
◦ Skin, hands, feet – 50,000 mrem/year (500 mSv)
◦ Cumulative – 1,000 mrem (10 mSv) X age in years
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Monitors worn on collar outside the
protective aprons
Interventional personnel use additional
monitor at waist level under the lead apron
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The National Council on Radiation Protection
and Measurements recommends using the
ALARA (As Low As Reasonably Achievable)
principle
◦ Try to keep exposure to less than 1/10
recommended dose limit
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Exposure levels—CR vertical, PA
projection, intensifier on top.*†
(Least exposure to operator)
operation
Vertical orientation with tube on top
(increases exposure to head and
neck of operator
—NOT recommended.
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Exposure levels—CR 30°
from vertical. *†
(CR angle increases
exposure to operator)
Exposure patterns and
levels—CR horizontal.*†
(Least exposure at
intensifier side)