Bone Densitometry of the Peripheral Skeleton With a New Photon Counting and Imaging Device

We present a new method for the assessment of bone mineral content of the peripheral skeleton. The method employs a new photon counting and imaging area device, the multi-wire proportional counter. The system can work as a single photon absorptiometer at the energies of both I-125 and Gd-153. It can work also as a dual photon absorptiometer using one of the two pairs of isotopes (I-125, Gd-153) or (I-125, Am- 241). Both the calcaneus and the forearm can be imaged in a few minutes, with either single or dual photon absorptiometry. To test this new method in a clinical environment we compared it with the standard dual photon absorptiometry of the forearm. The data collected in a cross-sectional study of bone mineral content and bone mineral density in a group of 76 patients show a good correlation between the two measurement techniques (r=0.931). The multi-wire proportional counter, due to its imaging capabilities, has a much lower repositioning error. This allows its use in regions with a large gradient of bone mineral density, such as the calcaneus or the very distal site of the forearm, which recent data have indicated to be superior to more proximal measurements in identifying osteoporosis.