Where is the ROI box typically placed during a DXA scan of the forearm?

• A. At the base of the radius
• B. At the tip of the ulna
• C. At the midpoint of the forearm
• D. At the wrist joint

Answer: (B)

In a DXA scan of the forearm, the ROI (Region of Interest) box is strategically placed at the tip of the ulna to accurately assess bone mineral density in that area. This location is significant because the distal ulna is particularly prone to osteoporotic fractures, making it an important site for evaluating bone health.

Positioning the ROI at the tip of the ulna ensures a focus on the area where the most meaningful measurements can be taken, as it reflects the trabecular bone that is largely responsible for strength and integrity in this section of the forearm. This choice is consistent with the anatomical focus on regions that have a higher risk of fracture due to osteoporosis, allowing for early detection and management of bone density issues.

The consideration of other landmarks, such as the base of the radius, the midpoint of the forearm, or the wrist joint, does not target the specific area of clinical concern as effectively as the tip of the ulna does.