Variability in Body Shape, Superficial Soft Tissue Geometry, and Seatbelt Fit Relative to the Pelvis in Automotive Postures-Methods for Volunteer Data Collection With Open Magnetic Resonance Imaging.

Variability in body shape and soft tissue geometry have the potential to affect the body's interaction with automotive safety systems. In this study, we developed a methodology to capture information on body shape, superficial soft tissue geometry, skeletal geometry, and seatbelt fit relative to the skeleton-in automotive postures-using Open Magnetic Resonance Imaging (MRI). Volunteer posture and belt fit were first measured in a vehicle and then reproduced in a custom MRI-safe seat (with an MR-visible seatbelt) placed in an Open MR scanner. Overlapping scans were performed to create registered three-dimensional reconstructions spanning from the thigh to the clavicles. Data were collected with ten volunteers (5 female, 5 male), each in their self-selected driving posture and in a reclined posture. Examination of the MRIs showed that in the males with substantial anterior abdominal adipose tissue, the abdominal adipose tissue tended to overhang the pelvis, narrowing in the region of the Anterior Superior Iliac Spine (ASIS). For the females, the adipose tissue depth around the lower abdomen and pelvis was more uniform, with a more continuous layer superficial to the ASIS. Across the volunteers, the pelvis rotated rearward by an average of 62% of the change in seatback angle during recline. In some cases, the lap belt drew nearer to the pelvis as the volunteer reclined (as the overhanging folds of adipose tissue stretched). In others, the belt-to-pelvis distance increased as the volunteer reclined. These observations highlight the importance of considering both interdemographic and intrademographic variability when developing tools to assess safety system robustness.

Methodology to measure seat belt fit in relation to skeletal geometry using an upright open MRI.

OBJECTIVE: Poor seat belt fit can result in submarining behavior and injuries to the lower extremity and abdomen. While previous studies have explored seat belt fit relative to skeletal landmarks using palpation, medical imaging remains the gold standard for visualizing and locating skeletal landmarks and soft tissues. The goal of this study was to create a method to image automotive postures and seat belt fit from the pelvis to the clavicle using an Upright Open MRI. METHODS: The posture and belt fit of 10 volunteers (5M, 5F) were measured in an Acura TLX in each subject's preferred driving posture and a standard reclined posture, and then reproduced in a custom non-ferromagnetic seat replica in the MR scanner with an MRI-visible seat belt. The MRI sequence and coil placement were designed to yield clear visualization of bone, soft tissue borders, and the seat belt markers in separate scans of the pelvis, lumbar, thoracolumbar, and thoracic regions. A process was developed to precisely register the scans, and methods for digitizing spinal and pelvic landmarks were established to quantify belt fit. CONCLUSIONS: This method creates opportunities to study variation in seat belt fit in different automotive postures, for occupants of different sexes, ages, BMIs, anthropometries, and for pregnant occupants.