The right calf of a single male volunteer, was imaged using a 0.2T MR system (Artoscan). The subject sat with the leg horizontal, supported at the ankle to avoid compression of the calf. The experimental procedure is described in detail elsewhere [3]. A phantom of known dimensions was used to remove geometric distortions from the images using a novel non-rigid registration algorithm [4]. The undistorted image of calf cross-section is shown in Fig. 1a.