DEXA Radiation Safety & Patient Preparation 4 — Questions and Answers
Question 1: A patient with a pacemaker reports for a DEXA scan. How should the technologist proceed?
- Refuse the scan; pacemakers are an absolute contraindication
- Proceed with the scan; DEXA poses no known risk to pacemakers (Correct answer)
- Perform only a peripheral forearm scan to avoid the chest
- Consult the cardiologist before performing the scan
Correct answer: Proceed with the scan; DEXA poses no known risk to pacemakers
DEXA uses very low-dose X-rays with no electromagnetic fields that would interfere with pacemaker function, so the scan can proceed normally.
Question 2: To reduce scatter radiation exposure to a DEXA technologist operating a pencil-beam unit, the best practice is to:
- Stand as close as possible to monitor image quality
- Step back or stand behind a shield during the scan (Correct answer)
- Wear a thyroid collar as the only protective device
- Perform scans only with the door closed
Correct answer: Step back or stand behind a shield during the scan
Distance is one of the most effective methods of reducing scatter radiation exposure; stepping back or positioning behind a barrier significantly lowers dose.
Question 3: Which of the following implants would MOST significantly interfere with lumbar spine DEXA measurement accuracy?
- Intrauterine device (IUD)
- Dental fillings
- Spinal fusion hardware and rods (Correct answer)
- Knee replacement
Correct answer: Spinal fusion hardware and rods
Spinal fusion hardware directly overlaps the lumbar vertebrae in the scan field, making accurate BMD measurement of those levels impossible.
Question 4: If a patient cannot lie flat due to kyphosis, what alternative scan site would the technologist typically prioritize?
- Calcaneus (heel)
- Proximal femur (hip)
- Distal radius (forearm) (Correct answer)
- Patella
Correct answer: Distal radius (forearm)
The distal radius can be scanned with the patient seated, making it an appropriate alternative when standard positioning is not feasible.
Question 5: How often should a DEXA phantom calibration scan be performed to ensure equipment accuracy?
- Once per week
- Before each patient examination or daily (Correct answer)
- Once per month
- Only after equipment servicing
Correct answer: Before each patient examination or daily
Daily phantom scans are the standard quality control practice to detect any drift in DEXA system calibration before patient scans are performed.
Question 6: A patient recently started taking oral corticosteroids. Why is this clinically significant for a DEXA technologist to document?
- Corticosteroids increase radiation sensitivity
- Long-term corticosteroids are a major cause of secondary osteoporosis (Correct answer)
- Corticosteroids interfere with DEXA calibration
- Corticosteroids increase artifact on bone images
Correct answer: Long-term corticosteroids are a major cause of secondary osteoporosis
Chronic corticosteroid use causes significant bone loss and is one of the most common causes of secondary osteoporosis, which is important clinical context for BMD interpretation.
Question 7: What is the purpose of positioning a patient with their legs elevated on a positioning block during a lumbar spine DEXA scan?
- To decrease radiation scatter to the gonads
- To flatten the lumbar lordosis and improve image quality (Correct answer)
- To reduce patient movement during scanning
- To align the femoral neck with the X-ray beam
Correct answer: To flatten the lumbar lordosis and improve image quality
Elevating the legs flattens the natural lumbar lordosis, bringing the lumbar spine parallel to the detector and improving bone density measurement accuracy.
DEXA Radiation Safety & Patient Preparation 4
A patient with a pacemaker reports for a DEXA scan.
How should the technologist proceed?