MR image acquisition was performed at Fukuoka Dental Collage. All the examinations were performed on a 1.5 T scanner (Intera Achieva nova dual; Philips Medical Systems, Eindhoven, the Netherlands) that used a sensitivity‐encoding SENSE‐Flex‐M coil. The muscle functional acquisitions were contiguous 4‐mm axial scans collected from the cricoid to the hard palate utilizing a spin‐echo sequence with a repetition time (TR) of 2000 ms and dual echo times (TE) of 10, 20, 30, 40, 50, 60, 70, and 80 ms. We obtained the T2 maps using the fast spin‐echo (FSE) sequence before, during, immediately after, and 20 min after clenching.
T2‐weighted MR images were obtained before and immediately after each motor task (at rest and after clenching) to measure any changes in the T2 values of the masseter muscles induced by clenching (Figure1a,c ). An average T2 of the anatomic region of interest (ROI) was determined by digitizing the region of the enhanced masseter muscle, which provided a computer‐generated average of T2. Digitizing was performed by one investigator (M.A.). Muscle segmentation was carried out using Osirix (v.3.9.4 32‐bit), a software program for digital imaging and communication in medicine.
T2‐weighted MR images were obtained before and immediately after each motor task (at rest and after clenching) to measure any changes in the T2 values of the masseter muscles induced by clenching (Figure