What is the optimal wavelength range used in DXA measurements?

• A. 10-20 keV
• B. 20-30 keV
• C. 30-40 keV
• D. X-ray photons typically at 40-70 keV

Answer: (D)

The optimal wavelength range used in DXA (Dual-Energy X-ray Absorptiometry) measurements typically falls within the range of 40-70 keV. This range is particularly effective for measuring bone mineral density because it allows for accurate differentiation between bone mineral content and soft tissue.

The use of these X-ray photon energies is important as they provide good penetration through soft tissues while still enabling precise measurement of bone density. Lower energies may not penetrate enough to provide reliable measurements, while higher energies could result in reduced contrast between bone and surrounding tissues, thus affecting the accuracy of the density readings.

The choice of 40-70 keV aligns well with the physics of how X-rays interact with different materials, particularly in the context of assessing bone structure versus soft tissue. This is crucial for obtaining accurate bone density measurements, which are essential for diagnosing conditions like osteoporosis and assessing fracture risk.