AMPDXA for Precision Bone Loss Measurements on Earth and in Space

one loss and its strength-related implications are major health concerns for our aging earthbound population and for astronauts exposed to microgravity during long-duration spacefl ight. Key to understanding the causal mechanisms of both age-related osteoporosis and microgravity-induced bone loss is the ability to make precision bone loss and bone structural measurements. The Advanced Multiple-Projection Dual-energy X-ray Absorptiometry (AMPDXA) scanning system is being developed at APL to meet this need. This article describes the development of the AMPDXA system, funded by the National Space Biomedical Research Institute (NSBRI), over the last several years, including progress made in human bone imaging, bone mineral density determination, and bone structural measurements. It also presents general information on bone loss, the effi cacy of bone loss countermeasures, and the inherent differences between age-related osteoporosis and microgravity-induced bone loss. The current effort will continue for the next 4 years and will culminate in the delivery to the NSBRI and NASA of a ground-based clinical system suitable for pre- and postfl ight testing of astronauts.