QUANTITATIVE CT AND MRI-BASED MODELING ASSESSMENT OF DYNAMIC VERTEBRAL STRENGTH AND INJURY RISK FOLLOWING LONG-DURATION SPACEFLIGHTPROLONGED PERIODS OF NEAR WEIGHTLESSNESS CAN CAUSE DAMAGE TO ASTRONAUTS MUSCULOSKELETAL SYSTEM. THIS DAMAGE CAN INCREASE THE RISK OF SKELETAL TISSUE FAILURE (E.G. FRACTURES TEARS) WHEN EXPERIENCING FORCEFUL DYNAMIC LOADS. FRACTURES OF THE SPINE DURING DYNAMIC CONDITIONS SUCH AS LAUNCH OR LANDING COULD CAUSE A MISSION TO FAIL. THIS STUDY WILL MEASURE THIS DEGRADATION OF ASTRONAUTS VERTEBRAE AND SPINAL MUSCLES DURING MISSIONS ABOARD THE INTERNATIONAL SPACE STATION (ISS). WE WILL THEN DETERMINE THE EXTENT OF VERTEBRAL WEAKENING OF CREWMEMBERS DURING LONG-DURATION MISSIONS.CHANGES IN PRE- AND POST-FLIGHT VERTEBRAL GEOMETRY VOLUME CORTEX THICKNESS AND BONE MINERAL DENSITY WILL BE MEASURED FROM EXISTING LUMBAR QUANTITATIVE COMPUTED TOMOGRAPHY (QCT) SCANS AS WELL AS FROM PLANNED QCT SCANS OF THE CERVICAL THORACIC AND LUMBAR SPINE FROM SIX ISS CREWMEMBERS. LIKEWISE THE PRE- AND POST-FLIGHT SPINAL MUSCLE VOLUMES WILL BE ANALYZED USING BOTH EXISTING MAGNETIC RESONANCE IMAGING (MRI) SCANS AND PLANNED MRI SCANS FROM SIX ISS CREWMEMBERS. THE QCT AND MRI SCANS WILL BE ANALYZED TODETERMINE STRUCTURAL AND MATERIAL CHANGES IN THE CERVICAL THORACIC AND LUMBAR VERTEBRAE AND THE SPINAL MUSCLES THAT INDICATE DAMAGE WHICH COULD WEAKEN THESE TISSUES.OUR UNIQUE ENGINEERING APPROACH WILL MEASURE THE LOSS OF VERTEBRAL STRENGTH DURING SPACEFLIGHT CONDITIONS AND PREDICT THE RISK OF FAILURE DURING TRAUMATIC DYNAMIC LOADING CONDITIONS SUCH AS LAUNCH OR LANDING. VERTEBRAL STRENGTH AND RISK FOR VERTEBRAL FRACTURE AND INJURY WILL BE QUANTIFIED IN 900 DYNAMIC SIMULATIONS USING A FULL HUMAN BODY MODEL THAT IS CONSTRUCTED USING STRUCTURAL AND MATERIALDATA GATHERED FROM THE PRE- AND POST-FLIGHT MEDICAL IMAGES FOR EACH ASTRONAUT.THIS STUDY HAS SIGNIFICANCE IN QUANTIFYING AND ADDRESSING RISKS OF LONG-DURATION SPACEFLIGHT INCLUDING VERTEBRAL INJURY FROM DYNAMIC LOADS VERTEBRAL FRACTURE EARLY ONSET VERTEBRAL OSTEOPOROSIS DUE TO SPACEFLIGHT AND IMPAIRED PERFORMANCE DUE TO REDUCED SPINAL MUSCLE MASS STRENGTH AND ENDURANCE.