DEXA Radiation Safety & Patient Preparation 2 — Questions and Answers
Question 1: A pregnant patient arrives for a DEXA scan ordered by her physician. What is the most appropriate action?
- Proceed with the scan as ordered
- Postpone the scan and notify the referring physician (Correct answer)
- Perform only the spine portion of the scan
- Reduce the scan speed to lower radiation dose
Correct answer: Postpone the scan and notify the referring physician
DEXA scans are contraindicated in pregnancy due to ionizing radiation exposure to the fetus, so the referring physician must be notified to reassess the order.
Question 2: Which of the following personal monitoring devices is MOST commonly used to track cumulative radiation dose for DEXA technologists?
- Geiger-Müller counter
- Ionization chamber survey meter
- Thermoluminescent dosimeter (TLD) badge (Correct answer)
- Scintillation detector
Correct answer: Thermoluminescent dosimeter (TLD) badge
TLD badges are the standard personal dosimetry device worn by radiation workers to measure and record cumulative occupational exposure.
Question 3: What is the primary reason DEXA uses dual-energy X-ray rather than single-energy X-ray?
- To reduce patient radiation dose
- To differentiate bone mineral from soft tissue (Correct answer)
- To increase image resolution
- To shorten scan acquisition time
Correct answer: To differentiate bone mineral from soft tissue
Dual-energy X-ray allows mathematical subtraction of soft tissue attenuation, isolating bone mineral density values accurately.
Question 4: A patient states she had a barium enema two days ago. How should the technologist proceed with the scheduled DEXA scan?
- Proceed immediately; barium does not affect DEXA
- Reschedule for at least 7 days post-procedure (Correct answer)
- Scan the hip only, avoiding the spine
- Reduce the X-ray energy setting to compensate
Correct answer: Reschedule for at least 7 days post-procedure
Residual barium in the gastrointestinal tract can falsely elevate lumbar spine BMD results, so the scan should be rescheduled until the barium has cleared.
Question 5: Which regulatory body sets the annual occupational radiation dose limit of 50 mSv for radiation workers in the United States?
- FDA
- CDC
- NRC (Correct answer)
- OSHA
Correct answer: NRC
The Nuclear Regulatory Commission (NRC) establishes radiation protection standards, including the 50 mSv annual occupational dose limit.
Question 6: Before a lumbar spine DEXA scan, the technologist notices the patient is wearing a metal belt buckle. What is the correct action?
- Angle the scan to avoid the buckle area
- Ask the patient to remove the belt (Correct answer)
- Note it in the report and proceed
- Cover the buckle with a lead shield
Correct answer: Ask the patient to remove the belt
Metal objects in the scan field can cause artifacts and falsely elevate BMD readings, so they must be removed before scanning.
Question 7: The ALARA principle in DEXA practice primarily means the technologist should:
- Always use the highest kVp available for best image quality
- Keep radiation exposure as low as reasonably achievable (Correct answer)
- Limit scan time to less than one minute per region
- Apply lead aprons to all patients regardless of scan type
Correct answer: Keep radiation exposure as low as reasonably achievable
ALARA (As Low As Reasonably Achievable) requires minimizing radiation dose while still obtaining diagnostically useful results.
DEXA Radiation Safety & Patient Preparation 2
A pregnant patient arrives for a DEXA scan ordered by her physician.
What is the most appropriate action?