Bone densitometry measures the strength and density of bones. Changes in trabecular bone mineral density (BMD) is an early indicator of change in metabolic function. Bone densitometry measures the amount of calcium in regions of the bones. A bone densitometer is used to determine the risk of developing osteoporosis and can also be used to estimate a patient's risk of fracture.
Bone densitometry methods involve:
Dual energy x-rays (DEXA) or CT scans (Osteo CT or QCT) compare the numerical density of the bone (calculated from the image), with empirical data bases of bone density. DEXA is widely available and has an accuracy between those of QCT and ultrasound.

An Osteo CT or quantitative computed tomography (QCT) is used to measure bone mineral density (BMD). The high contrast discrimination of computed tomography can be used to examine the central skeleton for osteoporosis. Common CT scanners require a standard of reference to properly perform quantitative tissue analysis.
Osteo CT is the most accurate bone densitometry study, but is not widely available and delivers more radiation to the patient than dual energy x-ray absorptiometry.

Densitometry is a method to image the density of for example, the bones to measure the mineral content or lung tissue to quantify emphysema.
Densitometry is also used to control the optical density of x-ray films by shining light on the film and measuring the transmission with a densitometer.

See also Bone Densitometry and Osteo CT.