A study of development of digital X-ray radiograpy technique for temporomandiblar joint (reconstruction of tomographic images, using X-ray TV system)

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The purpose of this study was to get multiple slice of tomographic images of TMJ, by applying the digital image processing to the image sequence of only single hypocycloidal tomographic scan, and to realize 3D display of TMJ, and 3D measurement of condyle-fossa-distance(CFD), using these tomographic images.For preprocessing, correction method of X-ray TV image distortion was developed by image processing software.Two digital image processing method for reconstruction of tomographic image were made. One is a method which use shift of image for reconstruction of tomographic image. Another is one, which use a 3D back projection (2D back projection is applied in X-ray CT) for reconstruction of tomographic image. In comparison of these two methods, image shift method was better than 3D backprojection method concerning reconstruction time in this system. Application of edge enhance processing to all the X-ray TV image before reconstructing the tomographic image was sharpened, and blur was re … More duced, and true border line of TMJ became easily recognizable.Using 42 slices of TMJ image at a interval of 0.5mm, reconstructed on this system, true border line of TMJ was traced, and 3D coordinates of condyle and fossa were digitized. According to these 3D coordinates, 3D images of TMJ were displayed on the CRT of graphic terminal LEX-90. Wire-frame method, constant shading method, and smooth shading method were implemented for 3D display of TMJ. For allowance to see the back-facing condylar head, translucent mode was applied for a rendering the fossa. As a result, the relationship between fossa and condyle was able to be recognized visually. In addition, 3D measurement of CFD was performed, and these values were mapped on the 3D TMJ display. This 3D coior display makes it easy to recognize the dislocation of condyle.For next step, introduction of array processor or digital signal processor to this system is desirable for improvement of the system performance, and development of the new image processing method is worth doing for getting a shsrper tomographic image. Less