High-resolution magnetic resonance imaging and diffusion tensor imaging of the porcine temporomandibular joint disc.

OBJECTIVES Diffusion tensor imaging (DTI) is an MRI modality for characterizing the property, microstructural organization and function in tissues such as the brain and spinal cord. Prior to this investigation, DTI had not been adapted for studies of the temporomandibular joint (TMJ) disc. Objectives were to test the feasibility of DTI to evaluate the porcine TMJ disc and to use DTI to observe differences in magnitude of anisotropy of water diffusion between TMJ disc regions. METHODS Five adult pig TMJs were scanned on a 9.4 Tesla horizontal bore MRI scanner using an inductively coupled surface coil. High-resolution gradient-echo and diffusion-weighted spin-echo based images were obtained. The mean diffusivity and fractional anisotropy (FA) were computed in different regions of the disc. Two observers were calibrated to review the two-dimensional and three-dimensional images. Polarized light microscopy was used as the gold standard for collagen fibre orientation. RESULTS In the sagittal plane, the mean diffusivity was higher in the posterior (1.28+/-0.10 x 10(-3) mm(-2) s(-1)) and anterior (1.27+/-0.08 x 10(-3) mm(-2) s(-1)) bands compared with the intermediate zone (0.96+/-0.01 x 10(-3) mm(-2) s(-1)), and the FA index was also lowest in the intermediate zone. In the coronal plane, the mean diffusivity was higher in the medial (1.42+/-0.01 x 10(-3) mm(-2) s(-1)) and lateral (1.21+/-0.12 x 10(-3) mm(-2) s(-1)) aspects than in the centre (1.09+/-0.08 x 10(-3) mm(-2) s(-1)), and the FA index was also lowest in the centre. CONCLUSIONS DTI is a useful method for non-invasively characterizing the structure/property relationships of the porcine TMJ disc.