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

本研究的目的是通过对单次次摆线层析扫描的图像序列进行数字图像处理，获得TMJ的多层层析图像，并利用这些层析图像实现TMJ的三维显示和髁-窝距离（CFD）的三维测量。在预处理方面，利用图像处理软件开发了x射线电视图像畸变的校正方法。提出了两种用于层析成像重建的数字图像处理方法。一种是利用图像移位对层析图像进行重建的方法。另一种是利用三维背投影（x射线CT采用二维背投影）重建层析图像。对比两种方法，在本系统中，图像移位法在重建时间上优于三维背投影法。对重建前的所有x射线电视图像进行边缘增强处理，对图像进行锐化处理，消除模糊，使TMJ的真实边界线易于识别。利用在该系统上重建的42张间隔0.5mm的TMJ图像，追踪TMJ的真边线，数字化髁突和窝的三维坐标。根据这些三维坐标，在LEX-90图形终端的CRT上显示TMJ的三维图像。采用线框法、恒定着色法和平滑着色法对TMJ进行三维显示。为了能够看到背朝髁头，半透明模式被应用于渲染窝。结果，能直观地识别窝与髁间的关系。此外，还进行了CFD的三维测量，并将这些数值映射到三维TMJ显示器上。这种三维彩色显示器可以很容易地识别髁突脱位。下一步，在该系统中引入阵列处理器或数字信号处理器可以提高系统的性能，开发新的图像处理方法可以获得更清晰的层析图像。少

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