Bone density tests, which measure the number of grams of calcium and other bone minerals in a segment of bone, determines the risk of osteoporosis. Osteoporosis presents with low bone mass and deterioration of bone tissue, resulting in increased risk of fractures. Physicians consider the bone density test an accurate predictor of the risk of fracture from osteoporosis. Several methods of testing may be used, including ultrasound, quantitative computed tomography and dual energy x-ray absorptiometry.
Ultrasound
Ultrasound offers a cost effective method of testing bone density by measuring bone mass through the speed of sound and broadband ultrasonic attenuation. Machines currently available in the United States detect bone mass in heel and tibia, useful because heel measurements are similar to spinal measurements. In addition to being inexpensive, ultrasound machines afford physicians a portable option that doesn't use ionizing radiation.
Quantitative Computed Tomography
Quantitative computed tomography, or QCT, primarily detects bone mass in the lumbar spine. It offers the advantage of measuring true volumetric density and is less likely to detect aging features that do not contribute to bone density measurements. The disadvantages include the possibility of confusion about bone marrow space changes associated with aging, radiation exposure and the high cost of its use. According to the University of Washington, QCT measurements decrease quickly with aging, resulting in lower "T" scores than with other bone density testing methods.
Dual Energy X-ray Absorptiometry
Dual-energy x-ray absorptiometry, also called DXA and bone densitometry, measures bone loss through an enhanced form of x-ray technology. Physicians utilize DXA more than any other form method of testing, although it does expose patients to small amounts of ionizing radiation. This testing method is often used on the lower spine and hips and occasionally on the entire body.
