Areal BMD measurements by DXA are reported in which unit?

• A. mg/cm^3
• B. g/cm^2
• C. kg/m^2
• D. µg/mm^2

Answer: (B)

DXA gives areal BMD, which is bone mineral content per projected area. Because it’s a 2D measurement, the density is expressed as mass per unit area. The standard clinical unit for this is grams per square centimeter, so g/cm^2 is the correct choice. If density were reported per volume (mg/cm^3), that would reflect a volumetric density used by CT-based methods, not DXA. While other area-density units like μg/mm^2 exist, the conventional reporting for DXA areal BMD is g/cm^2.