In what manner is Dual-Energy X-ray Absorptiometry (DXA) measured?

• A. Areal
• B. Volumetric
• C. Linear
• D. Two-dimensional

Answer: (A)

Dual-Energy X-ray Absorptiometry (DXA) measures bone mineral density in an areal fashion. This means that the results are expressed as grams of mineral per square centimeter (g/cm²). The DXA scan utilizes two different X-ray energy levels to differentiate between bone and soft tissue, which allows for the assessment of the density of bone in a specific area.

Areal measurement is particularly useful in clinical settings because it provides a standardized way to evaluate bone health. By focusing on a defined area, DXA can help detect conditions such as osteoporosis, where a reduction in bone density indicates a greater risk of fractures. The areal measurement does not provide the actual volume of bone but rather estimates bone density in terms of surface area, making it essential for the interpretation of results in relation to age, sex, and other demographic factors.

While volumetric measurements might seem plausible, they refer to the density of materials in three-dimensional space and aren't how DXA typically reports results. Linear and two-dimensional considerations are less relevant in the context of DXA, as DXA is fundamentally about assessing bone density in the two-dimensional surface area that the scan covers, emphasizing the areal aspect.