Biomechanics of Tissue Distortion and Stiffness by Magnetic Resonance Imaging

Compression of soft tissues and their deformation under externally applied forces are the limiting factors in the fitting of body support systems in orthotics and prosthetics and wheelchair seating. Tissue pressure and strain are also important determinants of comfort on beds and mattresses. Measurement of muscle cross-sectional area can also be used to estimate contraction strength and function in ergonomics. Through the use of magnetic resonance imaging (MRI), a safe and non-invasive method for measuring tissue shapes in vivo has become available. By observing the response of atomic nuclei in magnetic fields, this technique can reconstruct longitudinal and transverse views of internal tissue structures from skin surface to bony prominences (Crooks, 1985). Without any known harmful effects, magnetic resonance techniques can provide clear views of anatomy and pathology of internal body structures in the gravity environment of recumbent human subjects.