Bone densitometry, also called dual-energy X-ray absorptiometry, DEXA or DXA, uses a very small dose of ionizing radiation to produce pictures of the inside of the body (usually the lower (or lumbar) spine and hips) to measure bone loss. QCT is a fast, non-invasive bone mineral density (BMD) exam performed on a CT scanner. It allows us to look for low bone mass and monitor the effects of bone mass therapy in patients undergoing treatment.