Quantitative Aspects of Bone Densitometry-9BE06664

This ICRU report systematically addresses the quantities and units used in bone densitometry utilizing both x-ray and ultrasound techniques. For x-ray techniques the most important quantities are bone mineral density (BMD) and bone mineral mass (BMM), and for ultrasound techniques the speed of sound (SOS) or velocity of sound (VOS), and broadband ultrasonic attenuation (BUA). In the first section of the report these quantities are precisely defined in accordance with the SI system and ISO standards and ambiguities in their current use in the literature are addressed. For example, it is suggested that areal bone mineral density measured with dual energy x-ray absorptiometry (DXA) be indicated by a subscript "a" (BMDa) to differentiate it from the true volumetric quantity BMD measured by quantitative computed tomography (QCT). Another suggestion is the renaming of bone mineral content (BMC) to bone mineral mass (BMM).