Dual X-ray absorptiometry, known colloquially as a bone density scan, measures the density of bone using X-ray beams, according to WebMD, Bone density scans are often referred to as DXA or DEXA, duel energy X-ray absorptiometry.
DXA machines use both high- and low-energy X-ray beams to measure the thickness of bone. The amount of X-rays that pass through the bone is calculated for each beam, and the difference is calculated to measure the bone density, explains WebMD.
Doctors perform DXA scans to measure bone density of the hip and spine in patients at risk for osteoporosis, WebMD reports. Scans are generally easy to perform and expose patients to a relatively low amount of radiation.