Wikipedia
Amount of bone mineral in bone tissue
Summary
Bone density, or bone mineral density (BMD), is the amount of bone mineral in bone tissue, measured as mass of mineral per volume of bone. Clinically it is measured by proxy according to optical density per square centimetre of bone surface upon imaging. Bone density measurement is used in clinical medicine as an indirect indicator of osteoporosis and fracture risk. It is measured by a procedure called densitometry, often performed in the radiology or nuclear medicine departments of a hospital or clinic. The measurement is painless and non-invasive with low radiation exposure. Measurements are usually made over the lumbar spine and the upper part of the hip. The forearm may be scanned if the hip and lumbar spine are not accessible.