Longitudinal strain estimation in incompressible cylindrical tissues from magnetic resonance imaging.

In this paper, we present a simple approach for estimating the average longitudinal strains from models reconstructed from medical images. It can be used for many incompressible generalized cylindrical tissues, such as tendons, ligaments, and fusiform muscles; the major deformation directions of these soft tissues are along the longitudinal axes. The method is especially useful when pre- and post-deformation tissue correspondences are difficult to establish directly from images for various reasons, such as insufficient image resolution, homogenous image intensity, and noise. Incompressibility, which is accepted as a good approximation for soft tissues, is exploited as a constraint on the tissue deformation. Experiments with Magnetic Resonance Imaging (MRI) of tissue phantoms and computer simulations show that the method is accurate and practical even in the presence of noise. Finally, we demonstrate the usefulness of our approach on studying extraocular muscle deformation.