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J Clin Densitom. 2019 Aug 26. pii: S1094-6950(19)30121-0. doi: 10.1016/j.jocd.2019.08.005. [Epub ahead of print]

Use of Quantitative Computed Tomography to Assess for Clinically-relevant Skeletal Effects of Prolonged Spaceflight on Astronaut Hips.

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Biomedical Research & Environmental Sciences Division, NASA Johnson Space Center, Houston, TX, USA. Electronic address:
Biomedical Research & Environmental Sciences Division, KBR, Houston, TX, USA.
Department of Radiological Sciences, Department of Biomedical Engineering, and Department of Mechanical and Aerospace Engineering, University of California, Irvine, CA, USA.
University of Texas Medical Branch, Galveston, TX, USA.
Biomedical Research & Environmental Sciences Division, NASA Johnson Space Center, Houston, TX, USA.
Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA.



In 2010, experts in osteoporosis and bone densitometry were convened by the Space Life Sciences Directorate at NASA Johnson Space Center to identify a skeletal outcome in astronauts after spaceflight that would require a clinical response to address fracture risk. After reviewing astronaut data, experts expressed concern over discordant patterns in loss and recovery of bone mineral density (BMD) after spaceflight as monitored by dual-energy X-ray absorptiometry (DXA) and quantitative computed tomography (QCT). The pilot study described herein demonstrates the use of QCT to evaluate absence of recovery in hip trabecular BMD by QCT as an indicator of a clinically actionable response.


QCT and DXA scans of both hips were performed on 10 astronauts: once preflight and twice postflight about 1 wk and 1 yr after return. If trabecular BMD had not returned to baseline (i.e., within QCT measurement error) in 1 or both hips 1 yr after flight, then another QCT hip scan was obtained at 2 yr after flight.


Areal BMD by DXA recovered in 9 of 10 astronauts at 1 yr postflight while incomplete recovery of trabecular BMD by QCT was evident in 5 of 10 astronauts and persisted in 4 of the 5 astronauts 2 yr postflight.


As an adjunct to DXA, QCT is needed to detect changes to hip trabecular BMD after spaceflight and to confirm complete recovery. Incomplete recovery at 2 yr should trigger the need for further evaluation and possible intervention to mitigate premature fragility and fractures in astronauts following long-duration spaceflight.


Fracture risk; densitometry; recovery; spaceflight; trabecular bone


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