Why does a DXA unit require both high and low peak energy settings?

• A. To enhance image contrast for soft tissues only
• B. To allow separation between soft tissue and bone
• C. To improve the speed of the scanning process
• D. To reduce exposure time for patients

Answer: (B)

A DXA unit operates utilizing both high and low peak energy settings to enhance the separation between soft tissue and bone during a bone density scan. This dual-energy approach allows for the differentiation of materials based on their attenuation properties of X-rays at different energies. The high energy setting penetrates tissues better and is more focused on assessing the bone density, while the low energy setting is more sensitive to soft tissue.

By using these two energy levels, the DXA unit can effectively subtract the contribution of soft tissues when calculating bone mineral density. This is crucial because soft tissue can interfere with the accurate assessment of bone density, especially in areas like the lumbar spine or hip, where both bone and soft tissue are present. The accuracy of the measurements is paramount in diagnosing conditions like osteoporosis, making this dual energy technique essential for the reliability of the results.