DEXA Scan Operation & Technique 2 — Questions and Answers
Question 1: When performing a lumbar spine DXA scan, which vertebrae are typically included in the standard analysis region?
- L1 through L4 (Correct answer)
- L2 through L5
- T12 through L3
- L1 through L5
Correct answer: L1 through L4
The standard lumbar spine DXA analysis region is L1 through L4, as these vertebrae provide the most reliable BMD measurements.
Question 2: A patient has severe scoliosis affecting the lumbar spine. What is the most appropriate alternative site for BMD measurement?
- Femoral neck only
- Distal forearm (33% radius) (Correct answer)
- Calcaneus
- Thoracic spine
Correct answer: Distal forearm (33% radius)
The distal forearm (33% radius site) is the recommended alternative when the lumbar spine cannot be accurately measured due to scoliosis or other artifacts.
Question 3: What is the correct patient position for a proximal femur DXA scan?
- Hip externally rotated 15–20°, leg abducted
- Hip internally rotated 15–20°, leg abducted (Correct answer)
- Hip in neutral rotation, knee flexed
- Hip flexed 30°, leg straight
Correct answer: Hip internally rotated 15–20°, leg abducted
The femur must be internally rotated 15–20° and the leg slightly abducted to place the femoral neck parallel to the scan table for accurate measurement.
Question 4: Which of the following scan modes should be selected for a very thin patient (< 60 kg) undergoing a spine DXA scan?
- High definition mode
- Fast array mode
- Thin/standard mode (Correct answer)
- Thick mode
Correct answer: Thin/standard mode
A thin or standard scan mode should be used for low-BMI patients to ensure appropriate X-ray beam penetration and image quality.
Question 5: During a DXA scan, what does the technologist confirm by reviewing the scan image BEFORE releasing the patient?
- That the T-score is within normal range
- That positioning, ROI placement, and image quality are acceptable (Correct answer)
- That the patient's insurance has been verified
- That the report has been signed by a physician
Correct answer: That positioning, ROI placement, and image quality are acceptable
The technologist must review positioning, region-of-interest placement, and overall image quality before releasing the patient to ensure a repeat scan is not needed.
Question 6: What is the primary reason for using a foam positioning block between the patient's knees during a hip DXA scan?
- To keep the patient comfortable during a long scan
- To maintain consistent internal rotation and abduction of the femur (Correct answer)
- To reduce radiation scatter to the contralateral hip
- To align the pelvis with the table centerline
Correct answer: To maintain consistent internal rotation and abduction of the femur
The positioning block stabilizes the leg in the correct internal rotation and abduction, ensuring reproducible femur positioning for accurate BMD measurement.
Question 7: A DXA spine scan image shows an unexpectedly high BMD at L3 compared to adjacent vertebrae. What is the most likely cause?
- Patient moved during the scan
- Vertebral compression fracture or osteophytes at L3 (Correct answer)
- Incorrect scan mode selected
- Air gap between patient and table
Correct answer: Vertebral compression fracture or osteophytes at L3
Degenerative changes such as osteophytes or a compression fracture can artificially elevate BMD at an individual vertebra, making it appear denser than adjacent levels.
DEXA Scan Operation & Technique 2
When performing a lumbar spine DXA scan, which vertebrae are typically included in the standard analysis region?