measurement of the amount of calcium in bone. Most methods for measuring BMD (also called bone densitometry) are fast, noninvasive, painless, and available on an outpatient basis. Bone densitometry can also be used to estimate a patient's risk of fracture. BMD methods involve taking dual energy x-rays (DEXA) or CT scans of bones in the spinal column, wrist, arm, or leg. These methods compare the numeric density of the bone (calculated from the image) with empiric (historical) databases of bone density to determine whether a patient has osteoporosis, and, to what degree.