Optimal Contrast of Imaging Characteristics for 4 Dimensional MRI of the Temporomandibular Joint by Examining the Signal Intensity

The purpose of this study was to achieve optimal contrast of imaging characteristics in 4 dimensional MR images of the temporomandibular joint (TMJ) for evaluating the TMJ structures during mandibular movement. Twelve TMJs from six subjects without any TMJ dysfunction were studied. MRI was performed using a 1.5 MR system with an eight-channel phased array coil. The images were acquired using a balanced steady-state free precession (b-SSFP) sequence. The optimal flip angle was determined for differentiation for the main anatomical structures of the TMJ; the posterior band of the articular disc, the retrodiscal tissues, the condylar head, and the lateral pterygoid muscle, by examining the signal intensity (SI-d) of TMJ structures on b-SSFP MR images obtained using various flip angles. Repeated measures two-way analysis of variance (ANOVA) was performed, followed by Bonferroni's multiple comparison analysis. The main anatomical structures of the TMJ had the highest SI-d at flip angles of 30 degrees and 40 degrees, and there were the most significant differences between the SI-d of the articular disc and all other structures at a flip angle of 40 degrees, followed by a flip angle of 30 degrees. These data suggest that a flip angle of approximately 30 degrees to 40 degrees is appropriate for obtaining the optimal contrast of imaging characteristics for 4 Dimensional MR images of the TMJ with b-SSFP sequence.