Dependence on diffusion time of apparent diffusion tensor of ex vivo calf tongue and heart

Abstract

The time dependence of the apparent diffusion tensor of ex vivo calf heart and tongue was measured for diffusion times (τ_d) between 32 and 810 ms. The results showed evidence of restricted diffusion in the muscle tissues of both organs. In regions where the myofibers are parallel, the largest eigenvalue (λ₁) of the diffusion tensor remained the same for all diffusion times measured, while the other eigenvalues (λ₂, λ₃) decreased by 29–36% between τ_d = 32 ms and τ_d = 400 ms. In regions where the fibers cross, the λ₁ also changed, decreasing by 17% between τ_d = 32 ms and τ_d = 400 ms. The restricting compartment size and volume fraction were effectively estimated by fitting the time courses of the eigenvalues to a model consisting of a nonrestricted compartment and a cylindrically restricted compartment. To our knowledge, this study is the first demonstrating diffusion time dependence of measured water diffusion tensor in muscular tissue. With improvement in scanning technology, future studies may permit noninvasive, in vivo detection of changes in muscle myoarchitecture due to disease, treatment, and exercise. Magn Reson Med, 2005. Published 2005 Wiley‐Liss, Inc.