Tohoku J. Exp. Med., 2022 February, 256(2)

Application of Diffusion Tensor Imaging Fiber Tractography for Human Masseter Muscle

Takehiko Sugano,¹ Nobuhiro Yoda,¹ Toru Ogawa,¹ Teruo Hashimoto,² Kenta Shobara,¹ Kuniyasu Niizuma,^3,4,5 Ryuta Kawashima² and Keiichi Sasaki¹

¹Division of Advanced Prosthetic Dentistry, Tohoku University Graduate School of Dentistry, Sendai, Miyagi, Japan
²Institute of Development, Aging and Cancer, Tohoku University, Sendai, Miyagi, Japan
³Department of Neurosurgical Engineering and Translational Neuroscience, Graduate School of Biomedical Engineering, Tohoku University, Sendai, Miyagi, Japan
⁴Department of Neurosurgical Engineering and Translational Neuroscience, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan
⁵Department of Neurosurgery, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan

Diffusion tensor imaging (DTI) has been used to indicate the direction of nerve and muscle fibers by using the characteristics that water molecules preferentially diffuse along the fibrous structure. However, DTI fiber tractography for multipennate muscles, such as the masseter muscle, is challenging due to a lack of data regarding the imaging parameters. This study aimed to determine the optimal DTI parameters for masseter muscle fiber tractography. A 27-year-old healthy man voluntarily underwent DTI and T1-weighted magnetic resonance imaging of the right masseter muscle. Four imaging parameter settings were created by combining the following parameters that particularly affect the signal-to-noise ratio: b-value, number of excitations (NEX), and number of motion probing gradient (MPG) directions. DTI fiber tractography was performed using specific software for each parameter setting. The length and orientation of the muscle fibers in each layer were calculated. As a result, the masseter muscle fibers of each layer were identified on DTI. Although the detected fiber length was affected significantly by the imaging parameters, the fiber orientation was insignificantly affected. The appropriate combination of the b-value, NEX, and the number of MPG directions for masseter muscle fiber tractography could be determined based on previously reported anatomical data of the masseter muscle fibers. DTI may enable the non-invasive evaluation of masseter muscle fiber length and orientation. Elucidation of the details of masseter muscle fiber orientation is useful in evaluating stomatognathic biomechanics and muscle disorders.

Keywords —— biomechanics; diffusion tensor imaging; fiber tractography; magnetic resonance imaging; masseter muscle

© 2022 Tohoku University Medical Press

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Tohoku J. Exp. Med 2022, 256, 151-160.

Correspondence:Nobuhiro Yoda, Division of Advanced Prosthetic Dentistry, Tohoku University Graduate School of Dentistry, 4-1 Seiryo-machi, Aoba-ku, Sendai, Miyagi 980-8575, Japan.

e-mail: nobuhiro.yoda.e2@tohoku.ac.jp