PERIPHERAL QUANTITATIVE COMPUTED-TOMOGRAPHY FOR BONE-MINERAL MEASUREMENT WITH A NEW SPECIAL PURPOSE QCT-SCANNER - METHOD, NORMAL REFERENCES, COMPARISON TO OSTEOPOROTIC PATIENTS

Some years ago we designed a special purpose gamma-ray QCT scanner for bone mineral measurements at the forearm. Currently, the first commercially built scanners (Stratec SCT 900) are being tested and clinically evaluated. The scanner uses an I-125 photon source with a multidetector translate rotate fan beam geometry and newly developed semiconductor crystals. Quantification of trabecular bone and total bone at a standardized radial cross section gives an in-vivo reproducibility of < 1%, which is superior compared to all other bone mineral measurement techniques. In-vitro reproducibility is between 0.2 and 0.4 %, measured with calibration phantoms. The high in vivo reproducibility is ensured by automatic contour finding algorithms to determine the bone mass within a forearm cross sectional slice. A number of healthy men (n = 201) and women (n = 400) were examined to obtain a reference population for comparison to patients with generalized bone disease. We compared 182 osteoporotic females with healthy subjects. The high precision of the device and the high sensitivity of the measurement site considering changes of trabecular bone mass provide a very powerful means for monitoring bone mineral loss or changes due to therapy, as well as high diagnostic sensitivity.