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

本年度的研究计划包括三维重建、腺样体的三维测量、颅颌面硬组织和软组织的三维测量。本研究通过对11种正畸矫治器的磁共振成像中金属伪影的检测，以及5种正畸矫治器对颞下颌关节（TMJ）患者磁共振成像中金属伪影的检测，获得以下结果：1.除陶瓷托槽、镍钛丝外，大多数正畸矫治器（如托槽、钩、管附件、丝）在体模研究中都会产生严重的金属伪影。这些正畸矫治器在体模研究中产生的金属伪影从0.4 cm到11.9 cm不等.在临床实验中，A型患者的颞下颌关节MR成像是可行的。虽然大多数正畸患者都可以使用MR成像检查颞下颌关节，但作者建议正畸患者应使用表面线圈并拆除磨牙和钢丝的正畸装置进行准确的MR检查。我们使用重建图像分析了颅面形态的各种测量结果。特别是对腺样体进行了重点研究，腺样体是颌面部生长发育预测的重要指标。结果表明，10岁以下儿童的腺样体可分为Ⅰ ~ Ⅳ类，其中Ⅳ类腺样体在青年组的比例大于成年组。腺样体大小与腭扁桃体大小有关。此外，头颅X线片与MRI三维重建图像相叠加，可对颅颌面硬、软组织形态进行评价。

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.