The objectives of this project for the first year and the resulting progress on each objective is summarized below.
Objective 1. Obtain study approvals for the retrospective and prospective arms of the study.
Approvals for the retrospective and prospective arms of the study were obtained this year, including LSAH (Lifetime Surveillance of Astronaut Health), IRB (Institutional Review Board), and Flight Investigation approvals.
Objective 2. Acquire and analyze retrospective pre- and post-flight medical images to quantify vertebral and spinal muscle changes.
Retrospective quantitative computed tomography (qCT) scans from 16 crewmembers were received from the LSDA (Life Sciences Data Archive)/LSAH in March and July 2017. Pre-flight and post-flight qCT scans were available for 16 subjects, with follow-up qCT scans at 1, 2, 3, and 4 years for select subjects. The 16 pre-flight,16 post-flight, and 27 annual follow-up qCT scans of L1 and L2 vertebrae were segmented using a semi-automated process to create 3D models of the vertebrae. Each qCT scan was processed with an algorithm to quantify the cortical thickness of the L1 and L2 vertebrae, mapping these thicknesses onto the 3D vertebral surface models. Analysis of the cortical thickness data is ongoing.
The psoas, paraspinal, and quadratus lumborum muscle groups are in the process of being segmented and analyzed from the retrospective qCT scans to characterize muscle geometry, volume, and fat infiltration changes in crewmembers of long-duration spaceflight. Segmentation of the psoas, paraspinal, and quadratus lumborum muscles, including fat infiltration, has been completed for 16 of the 59 qCT scans. Analysis of muscle geometry, volume, and fat infiltration changes for pre-flight, post-flight, and follow up scans is in progress.
Retrospective magnetic resonance imaging (MRI) scans of the cervical spine and lumbar spine of 6 crewmembers were received from the LSDA/LSAH in June 2017. All crewmembers underwent both a pre-flight and a post-flight scan. Analysis of these scans to quantify spinal muscle changes from pre- to post-flight is in progress.
Objective 3. Prepare the medical image protocols and procedures for the prospective arm of the study.
A parametric experiment with a cadaver was conducted to vary qCT scan parameters and examine the resulting image quality and radiation dosage. The objective was to determine a set of scanning parameters that produced adequate image quality to measure bone outcomes, while reducing the radiation exposure to the research participant. The cadaver underwent 14 qCT scans of the C1-L5 region and the following scan parameters were varied: tube voltage, tube current, and pitch. Volumetric bone mineral density measures from each of these scans were compared to a qCT scan acquired with standard parameters that are used clinically to assess accuracy. Using this data, we have finalized a qCT protocol to scan the C3, T3, and L1 vertebrae that produces accurate volumetric bone mineral density measurements with minimal radiation exposure (<1 mSv).
The MRI scan protocol was also finalized for the prospective arm of the study. T1 and T2 weighted MRI scans of the cervical, thoracic, and lumbar spine regions will be acquired to capture the spinal musculature surrounding the vertebral column.
Objective 4. Begin consenting crewmembers for the prospective arm of the study.
Consent briefings for potential crewmembers for the prospective arm of the study began in July 2017 and we are actively enrolling participants. To date, four consent briefings have been held or are scheduled.