Peripheral Quantitative Computerized Tomography or pQCT, is a relatively new bone measurement technology that provides information beyond that obtained by traditional DXA. This additional information includes area and bone mineral density of trabecular vs. cortical bone as well as estimates of bone strength (strength-strain index). pQCT scans can be obtained on peripheral sites including the tibia. Because pQCT can distinguish between cortical and trabecular bone (the latter of which loses bone preferentially with disuse), pQCT may prove to be a more sensitive measure than DXA for detecting disuse bone changes. If this is so, pQCT measurements might in the future allow for earlier acceptance or rejection of bone-related countermeasures than would be provided by DXA alone. JSC's long duration bed rest studies provide an important opportunity to validate the utility of pQCT measurements for monitoring disuse bone loss, with minimal associated time requirements or radiation exposure. In addition, pQCT provides important information regarding bone strength by measuring a strength-strain index for the scanned bone region. This information is not available with DXA.
This experiment has concluded in ground-based studies sponsored by the National Aeronautics and Space Administration's Human Adaptation and Countermeasures Division. This experiment was conducted during Bed Rest Campaigns 3A-3F and Campaign 5A - 5C and the Artificial Gravity Study.