Diffusion tensor imaging in the human calf muscle as a measure of the muscle disorder

The diffusion tensor imaging (DTI) is a method for the evaluation of water diffusion in organized tissues. In muscles the diffusion of water is expected to be anisotropic. It is hypothesized that diffusion is larger along muscle fibers compared to that across fibers. From a series of diffusion weighted images the diffusion tensor can be calculated. The obtained eigenvalues and eigenvectors of this tensor provide information about local muscle tissue anisotropy. The aim of this study was to determine whether DTI is a suitable method to characterize the extent of human calf muscle injuries such as tears, and the difference between immediate post‐exercise and at rest skeletal muscle. The data were collected using a GE‐3.0T shortbore scanner with a standard knee coil. Four subjects were investigated: one patient with chronic compartment syndrome affecting the posterior compartment of the calf, one patient with clinically apparent acute medial gastrocnemius tear, and two healthy volunteers. The diffusion anisotropy of water was characterized by the fractional anisotropy. The diffusion images demonstrate the anisotropy of the diffusion and the large contrast arising from the different orientations of the cells in the muscle tissue. The calculated eigenvalues of the diffusion tensor reflects the strong anisotropic character of the muscle tissue. The results of the fiber tractography method demonstrate disorder as expected for the muscle tear, while the healthy muscle shows the ordering in the fibers. As a conclusion, DTI and fibre tracking may be suitable techniques for analyzing skeletal muscle damage and evaluating lesion extent. © 2005, American Association of Physicists in Medicine. All rights reserved.