What is considered a disadvantage of DXA?

• A. High cost
• B. Inability to detect soft tissue
• C. Doesn't account for bone thickness
• D. Requires a larger patient size

Answer: (C)

The statement that the disadvantage of Dual-energy X-ray Absorptiometry (DXA) is that it doesn't account for bone thickness is valid within the context of evaluating bone density. DXA is highly regarded for its ability to measure bone mineral density and assess the risk of osteoporosis, but it operates under certain assumptions about bone geometry. One of these assumptions is that the bone has a uniform density, which means that variations in bone thickness may not be adequately captured by the DXA measurements.

This characteristic can affect the accuracy of the bone mineral density (BMD) readings, especially in individuals with atypical skeletal structures or those with bone shape abnormalities. If the thickness of the bone is not appropriately factored in, this could lead to misinterpretations or less accurate assessment of bone health.

In contrast, while DXA may also exhibit high costs, an inability to detect soft tissue effectively, and a requirement for appropriate patient positioning, these factors do not directly relate to the assessment of bone density in the same manner that bone thickness does. Therefore, focusing on the uniform density assumption highlights a core aspect of DXA's limitations when evaluating bone density values comprehensively.