VIR Radiation Safety & Protection 2 — Questions and Answers
Question 1: Where should the primary monitoring dosimeter badge be worn when a lead apron is used in the VIR suite?
- At the waist, underneath the lead apron
- At the collar level, outside the lead apron (Correct answer)
- On the wrist of the dominant hand
- On the forehead beneath the surgical cap
Correct answer: At the collar level, outside the lead apron
The primary dosimeter is worn at the collar level outside the apron to estimate dose to the unshielded head, neck, and thyroid—the highest-exposure unprotected regions.
Question 2: The lead equivalency of a standard full wrap-around lead apron used in interventional radiology is typically:
- 0.1 mm Pb equivalent
- 0.25 mm Pb equivalent
- 0.5 mm Pb equivalent (Correct answer)
- 1.0 mm Pb equivalent
Correct answer: 0.5 mm Pb equivalent
Standard lead aprons provide 0.5 mm Pb equivalent protection, which attenuates approximately 90–95% of scatter radiation at typical fluoroscopic energies.
Question 3: Which action most effectively reduces patient entrance skin dose during fluoroscopy?
- Keeping the image receptor as far from the patient as possible
- Placing the image receptor close to the patient (Correct answer)
- Using maximum kVp throughout the procedure
- Increasing the source-to-skin distance while moving the detector away
Correct answer: Placing the image receptor close to the patient
Placing the image receptor close to the patient prompts the automatic exposure control (AEC) to reduce X-ray output, thereby lowering patient entrance skin dose.
Question 4: Pulsed fluoroscopy reduces radiation dose compared to continuous fluoroscopy primarily because:
- It reduces tube voltage (kVp) during each pulse
- Radiation is only emitted during discrete pulses rather than continuously (Correct answer)
- It automatically collimates the beam to a smaller field
- It increases the source-to-patient distance
Correct answer: Radiation is only emitted during discrete pulses rather than continuously
Pulsed fluoroscopy delivers X-rays only during brief intervals rather than continuously, reducing total dose proportional to the duty cycle and the selected frame rate.
Question 5: The recommended annual occupational dose limit for the lens of the eye according to NCRP Report 116 is:
- 15 mSv (1.5 rem)
- 50 mSv (5 rem)
- 150 mSv (15 rem) (Correct answer)
- 500 mSv (50 rem)
Correct answer: 150 mSv (15 rem)
NCRP Report 116 recommends an annual occupational dose limit of 150 mSv (15 rem) for the lens of the eye, reflecting its sensitivity to radiation-induced cataract formation.
Question 6: Which practice most effectively reduces scatter radiation dose to the VIR operator's hands during procedures?
- Wearing lead gloves at all times during imaging
- Using long instruments to maintain maximum distance from the X-ray beam (Correct answer)
- Increasing the fluoroscopy frame rate to shorten total procedure time
- Switching from fluoroscopy to DSA for all imaging
Correct answer: Using long instruments to maintain maximum distance from the X-ray beam
Using longer instruments to keep hands at maximum distance from the primary beam is most effective, as the inverse square law provides significant dose reduction even with small increases in distance.
Question 7: The 'last image hold' (LIH) feature on fluoroscopy equipment is designed to:
- Record the highest dose rate achieved during the procedure for regulatory reporting
- Retain the final fluoroscopic frame on the monitor without continued radiation emission (Correct answer)
- Automatically optimize the next exposure based on prior image quality
- Store all images for the legally required retention period
Correct answer: Retain the final fluoroscopic frame on the monitor without continued radiation emission
Last image hold retains the final fluoroscopic frame on the monitor after the foot pedal is released, allowing anatomical review without generating additional radiation.
VIR Radiation Safety & Protection 2
Where should the primary monitoring dosimeter badge be worn when a lead apron is used in the VIR suite?