DETERMINATION OF LINGUAL MYOARCHITECTURE IN WHOLE TISSUE BY NMR IMAGING OF ANISOTROPIC WATER DIFFUSION

The muscular anatomy of the tongue consists of a complex three-dimensi onal array of fibers, which together produce the variations of shape a nd position necessary for deglutition. To define the myoarchitecture o f the intact mammalian tongue, we have utilized NMR techniques to asse ss the location and orientation of muscle fiber bundles through measur ement of the direction-specific diffusional properties of water molecu les. Whole sheep tongues were excised and imaged with a slice-selectiv e stimulated-echo diffusion sequence in the midline sagittal plane, an d three-dimensional diffusion tensors were determined for each voxel. The derived diffusion tensors were depicted graphically as octahedra w hose long axes indicate local muscle fiber orientation. Two distinct g roups of midline fibers were identified: I) in-plane sagittal fibers o riginating in the posteroinferior region of the tongue, radiating with a fanlike projection anteriorly and superiorly and merging with verti cally oriented fibers, and 2) cross-plane (transverse) fibers, oriente d at right angles to the vertically aligned fibers, predominantly in t he anterior and superior regions of the tongue. Regional comparison of diffusion anisotropy revealed uniform and parallel alignment thigh an isotropy) in the posteroinferior region of the tongue, corresponding t o the base of the genioglossus, and less uniform, orthogonally aligned fibers (low anisotropy) in the anterosuperior region of the tongue, c orresponding to the core intrinsic muscles. These data indicate that l ingual myoarchitecture, determined through direction-dependent mobilit y of water molecules, can be depicted as discrete regions of muscle fi bers, whose orientation and extent of diffusion anisotropy predict loc al contractility.