9. 4次元MRIを用いた顎関節部の評価 MR Fluoroscopyにおける撮像条件の検討

[I. Purpose] Recently, Magnetic Resonance Imaging Technique is remarkably progressive. Temporomandibular joint can be observed during mandibular opening and closing movement. We used 4 Dimensional MRI Technique to describe the movement by taking the image of opening and closing mouth 1 time, for evaluation of Temporomandibular joint. The purpose of this study was to establish the most suitable imaging characteristic of 2 Dimensional MR Fluoroscopy and 4 Dimensional MRI techniques with True-FISP sequence, by examination of the contrast of TMJ structures on imagings, for evaluation of the TMJ. [II. Materials and Methods] This study investigated in a TMJ of a man, without abnormality in the Temporomandibular function. MRI examinations were performed on a 1.5 Tesla MR System (Philips Company), with a Phased Array Coil. The images were acquired using 2 Dimensional MR Fluoroscopy Technique with True-FISP sequence. The Sagittal images of TMJ were taken in the closed mouth position, obtained by setting various Flip angles with 10-degree interval between 10 degree and 100 degree. The contrasts of the images were evaluated in 4 main anatomical structures of TMJ; Anterior band of Articular disc, Bilaminar zone, Condylar head, and Lateral Pterygoid muscle, with graph of Signal Intensity, graph of Signal-to-Noise Ratio (SNR),and Visual evaluation. [III. Results and Discussion] Main anatomical structures of TMJ had the highest Signal intensity at Flip angle 30 degree. Graph of SNR also showed the peak at Flip angle 30 degree, and all points were separate. On Visual evaluation, 4 anatomical structures of TMJ were also distinguished on the imaging at Flip angle 30 degree. These results suggest that at Flip angle approximate 30 degree is suitable for obtaining the optimal imaging characteristic for evaluation of the Temporomandibular joint region during mandibular movement by using 4 Dimensional MRI Technique with True-FISP sequence.