HOW WELL DOES DUAL PHOTON-ABSORPTIOMETRY PREDICT OSTEOPOROSIS - A COMPARISON BETWEEN NEUTRON-ACTIVATION ANALYSIS AND DEXA

The accuracy of dual energy X-ray absorptiometry (DEXA) for measuremen t for measurement of bone mass carried out by quantitative digital rad iography (Hologic Inc.) was compared to results with neutron activatio n analysis (NAA) on 106 subjects. The accuracy with DEXA was further i nvestigated by measurements on aluminium samples of known composition. DEXA measured 4 lumbar vertebrae by spine scan. The central third of the skeleton also was measured by whole body scan to obtain data on th e same large part of the skeleton as measured by NAA. Results suggeste d that DEXA spine scans were more reliable than whole body scans. [n a ddition, the measurement of total mineral content (BMC) was more relia ble than the normalization of BMC to bone surface area (BMC/Area) or b one mineral density (BDM). Since the proportion of bone below detectio n would increase with development of osteoporosis, with osteoporosis t he BMC would be increasingly underestimated, but to only a small exten t, while the BMD would be more significantly overestimated.