Detecting Rat Heart Myocardial Fiber Directions in X-ray Microtomography Using Coherence-Enhancing Diffusion Filtering

Because the electrical and mechanical properties of myocardial tissue are strongly anisotropic the local fiber direction is an important parameter for realistic computational models of cardiac excitation and motion. Within the last years Diffusion Tensor Imaging has been established as a noninvasive measuring technique for fiber directions from whole hearts ex vivo. X-ray microtomography offers a much higher spatial resolution than Diffusion Tensor Imaging and could scan a whole heart as well. The inherently low soft-tissue contrast can be enhanced through staining with iodine. We recorded a volumetric scan of a rat heart and filtered the imaging data with a coherence-enhancing anisotropic diffusion filter to enhance its microstructure. The filtering was performed in three dimensions. From the structure tensor of the filtered volumes scalar measurements and fiber tracts were calculated and used for visualization and further analysis.