DEVELOPMENT AND CLINICAL APPLICATION OF THREE DIMENSIONAL CEPHALOMETRY WITHOUT X-RAY IRRADIATION

今年的研究计划包括重建三维图像、腺样体三维测量、开发用于颅面形态硬组织和软组织测量的三维头颅显像。初步研究评估金属伪影，使用假体检查各种正畸矫治器（11种类型）MR图像上的金属伪影，并在临床实验中评估TMJ患者使用正畸矫治器（5种类型）的MR图像。得到了以下结果：1。除陶瓷支架、镍钛金属丝外，大多数正畸器具如支架、挂钩、管附件、金属丝等都会产生严重的金属伪影。这些正畸矫治器是由0.4厘米到11.9厘米的金属人工制品制成的。在临床实验中，虽然大多数使用正畸器具的患者可以使用磁共振成像检查TMJ，但作者建议使用正畸器具的患者应使用表面线圈并去除磨牙和金属丝等正畸器具以进行准确的磁共振检查。为了考虑三维重建图像在临床牙科中的应用，我们分析了使用重建图像的颅面形态学的各种测量值。我们特别关注腺样体，它是正畸医师诊断颌面部生长预测的重要指标。结果表明：10岁以下儿童腺样体分为1 ~ 4类，其中4类在青少年中所占比例大于成人。腺样体的大小与腭扁桃体的大小相关。此外，可以通过叠加脑电图和MRI三维重建图像来评估颅面形态学中的硬组织和软组织形态。

The research plan of this year is composed of reconstructive three dimensional images, three dimensional measurement of adenoid, and the development of three dimensional cephalogram for the measurement of hard tissue and soft tissue in craniofacial morphology. For the pilot study metal artifact was assessed to examine the metal artifacts on MR images of a variety of orthodontic appliances (11 types) using a phantom and to evaluate the MR images of TMJ patient with orthodontic appliances (5 types) on clinical experiments.The following results were obtained :1. Most orthodontic appliances such as bracket, hook, tube attachment, wire produced severe metal artifacts except for ceramic bracket, wire of NiTi on phantom study. These orthodontic appliances were produced metal artifacts ranging from 0.4 cm to 11.9 cm on phantom study.2. On clinical experiments, it was possible to examine the TMJ on MR imaging in Type A.Although most of patients with orthodontic appliances can examine the TMJ using MR imaging, authors recommend that patients with orthodontic appliances should use a surface coil and removing the orthodontic appliances of molar and wire for accurate MR examination.For considering the application of three dimensional reconstruction images to clinical dentistry, we analyzed various measurements of craniofacial morphology using reconstructive images. Especially we focused to adenoid which is an important for orthodontists to diagnose growth prediction of maxilloface. The results suggested that the under-ten generation had adenoid which classified four categories from I to IV, the ratio of category IV in young generation was larger than that in adult generation. The size of adenoid was associated with the size of palatal tonsil. Furthermore, it is possible to assess the hard and soft tissue morphology in craniofacial morphology by superimposing cephalogram and three dimensional reconstructive images of MRI.