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

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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.