Clinical Significance of Magnetization Transfer Contrast Imaging for Edematous Changes in Masticatory Muscle

Objective: To evaluate inflammatory changes in masticatory muscles by magnetization transfer contrast (MTC) imaging. Methods: Gradient-recalled echo (GRE) and MTC-GRE images of relaxed masticatory muscles in 28 healthy volunteers were obtained before and after exercise. At the same time, muscle stiffness and pain in the masseter muscles were also measured. Magnetization transfer ratios (MTRs) of the muscles were calculated from the GRE and MTC-GRE images. The MTRs of the masticatory muscles in 50 patients with temporomandibular disorder were compared with those in the volunteers. Results: Immediately after the exercise, the MTRs of the masseter muscles significantly decreased (P <0.05), whereas muscle stiffness and pain increased in the healthy volunteers. In patients with masseter muscle pain, the MTRs of the masseter muscles were significantly lower than in the healthy volunteers (P <0.05). Conclusions: Magnetization transfer contrast imaging strongly reflects the masticatory muscle edematous changes, possibly leading to masseter muscle pain.