DEXA Radiation Safety & Patient Preparation 3 — Questions and Answers
Question 1: A patient received a nuclear medicine bone scan 24 hours ago. How does this affect their DEXA appointment?
- No effect; proceed with the DEXA scan
- Postpone DEXA for at least 72 hours to allow radiopharmaceutical decay (Correct answer)
- Increase the DEXA scan speed to minimize additional dose
- Perform only peripheral DEXA instead of central DEXA
Correct answer: Postpone DEXA for at least 72 hours to allow radiopharmaceutical decay
Residual radiopharmaceuticals from a recent nuclear medicine study can interfere with DEXA measurements, requiring a waiting period for adequate decay.
Question 2: What effective radiation dose does a typical central DEXA scan (spine + hip) deliver to a patient?
- 0.001–0.01 mSv (Correct answer)
- 0.1–1.0 mSv
- 1–10 mSv
- 10–50 mSv
Correct answer: 0.001–0.01 mSv
A standard central DEXA scan delivers approximately 0.001–0.01 mSv, which is extremely low — less than a day of natural background radiation.
Question 3: Which patient condition would most likely cause a falsely ELEVATED lumbar spine T-score on DEXA?
- Severe scoliosis
- Vertebral compression fractures with collapse
- Osteophytes and aortic calcification (Correct answer)
- Low body weight
Correct answer: Osteophytes and aortic calcification
Osteophytes, aortic calcifications, and degenerative changes add density in the scan field, falsely elevating the measured BMD and T-score.
Question 4: Which of the following is NOT required information to gather during DEXA patient intake?
- History of recent fractures
- Current medications affecting bone density
- Patient's blood type (Correct answer)
- Height and weight
Correct answer: Patient's blood type
Blood type is not relevant to DEXA scanning; fracture history, bone-affecting medications, and anthropometric measurements are all clinically important.
Question 5: Why must patients be asked about recent oral contrast or CT contrast agents before a DEXA scan?
- Contrast agents increase patient radiation sensitivity
- Residual contrast can artificially alter BMD measurements (Correct answer)
- Contrast interferes with the DEXA table calibration
- IV contrast causes muscle artifact in the scan field
Correct answer: Residual contrast can artificially alter BMD measurements
Oral and IV contrast materials can remain in the body and affect X-ray attenuation, leading to inaccurate BMD values.
Question 6: A DEXA technologist working in a busy clinic should wear their dosimetry badge:
- Only when performing spine scans
- At collar level outside any lead apron during all scanning activities (Correct answer)
- Inside a lead apron to measure gonadal dose
- At waist level inside clothing for comfort
Correct answer: At collar level outside any lead apron during all scanning activities
Dosimetry badges should be worn consistently at collar level outside protective apparel to accurately record the head and neck dose, which is unprotected.
Question 7: When counseling a patient who expresses concern about radiation from DEXA, the technologist should explain that the DEXA dose is comparable to:
- A chest CT scan
- Several hours of natural background radiation (Correct answer)
- A standard mammogram
- An abdominal X-ray series
Correct answer: Several hours of natural background radiation
The DEXA effective dose is so low (≈1–10 µSv) that it is comparable to a few hours of exposure to natural background radiation.
DEXA Radiation Safety & Patient Preparation 3
A patient received a nuclear medicine bone scan 24 hours ago.
How does this affect their DEXA appointment?