QCT Bone Mineral Densitometry

QCT Bone Density is a method used to measure bone mass. It is one of the three methods cited by the National Osteoporosis Foundation as useful and safe in the evaluation of osteoporosis. A QCT bone mass measurement is used to assess osteoporosis in the same way a cholesterol measurement is used for coronary heart disease or blood pressure for stroke. The data are used to measure an important risk factor and determine the necessity, choice and efficacy of therapy.

How is QCT different from other methods?

QCT and DXA both measure spinal bone mass, a significant advantage over other methods, e.g. ultrasound, which measures bone in the peripheral skeleton where bone density is slow to change in response to disease therapy. Spinal bone is a mixture of high-turnover trabecular (spongy) bone and slowly-changing cortical (compact) bone. DXA measures the sum of these two compartments but also includes aortic calcification and osteophytes in the calculation of bone mineral in the spine. Only QCT isolates the metabolically-active trabecular bone for analysis. Lateral DXA, a newer approach, has recently been shown to have a sensitivity intermediate between the high sensitivity of QCT and the somewhat lower one of conventional DXA for detection of osteoporosis, but it uses 4-10 times the radiation exposure, is less precise, and the study time is increased compared to conventional DXA. New ultrasound methods for the knee or the heel are being used for osteoporosis screening, but unlike QCT or DXA they do not measure bone mass, and cannot be used to measure the spine where most osteoporotic fractures occur.