What is the most common site for quantitative ultrasound measurements?

• A. Femoral neck
• B. Os calcis (heel)
• C. Lumbar spine
• D. Radius

Answer: (B)

Quantitative ultrasound looks at how sound waves behave as they pass through bone, using measurements like speed of sound and attenuation to infer bone properties. The heel bone, or calcaneus, is the most common site for this test because it contains a large amount of cancellous (trabecular) bone, which responds quickly to changes in bone density and structure. It’s also easy to access, shallow, and allows rapid, radiation-free assessment with portable devices. Because of these practical and physiological advantages, the calcaneus serves as the standard site for QUS, providing useful information about fracture risk that often correlates with density in other skeletal sites. Other sites (like the hip, spine, or forearm) are more typical for DXA measurements rather than QUS due to movement toward more precise imaging with different modalities.