Use of probabilistic diffusion tractography to improve visualization in skeletal muscle tractography

One report found that visualization of tractography of the soleus muscle tended to be poorer in males than in females (1) This report also suggested that this sex difference in visualization resulted from differences in the size and variations in the pennation angle. Therefore, we concluded that there was a limitation to perfect visualization of muscles with a large and variable angle of pennation using skeletal muscle tractography generated by deterministic diffusion tractography. In particular, deterministic diffusion tractography has limitations in visualizing “tangled” muscle fibers (hereafter referred to as “tangled fibers”). A new method of tracking fibers, called probabilistic diffusion tractography (PDT) has been developed and is being used in neuroradiology to predict the presence of crossing fibers in the brain (2, 3). We have noticed that the crossing fibers in the brain and tangled fibers in skeletal muscle show morphological similarities at the microscopic level, which suggests that PDT might also help resolve difficulties in visualizing tangled fibers from using deterministic diffusion tractography. The purpose of this study was to perform skeletal muscle tractography using PDT to quantitatively evaluate its visualization ability. We also sought to elucidate whether visualization varies by muscle and whether differences in PDT scan parameters also affect visualization.