Theoretical analysis of diagnostic process of medical image and optimization of CRT image processing

本研究的目的是阐明在ORT观察站上判读CR（computed radiograph）胸部图像时，肺部细微异常表现的特征与观察者诊断性能之间的关系，优化各种图像处理，最终建立CRT诊断中最有效的图像处理方法。ORT监测器上细微肺异常的解释结果表明，高频增强并不一定有益，因为正常动脉经常模仿异常间质阴影。一般来说，低频增强处理优于高频增强。此外，尽管在传统胶片图像上检测到细微磨玻璃的存在，但由于图像处理不充分导致图像模糊，因此在软拷贝图像上可能会错过细微磨玻璃的存在。图像处理的效果因异常的类型和特征而异，观察者对图像处理效果的评价也存在差异。CRT显示器上的影像诊断具有可自由使用的图像处理的优点。然而，从传统的屏幕-胶片图像中发展出来的诊断标准及其过程并不一定直接应用于软拷贝图像。特别是高频增强处理往往导致胸部图像的过度诊断或欠诊断。

The purpose of this research is to clarify the relationship between the characteristic of subtle abnormal pulmonary findings and observer's diagnostic performance in the imagediagnostic process when CR(computed radiograph) chest image is interpreted on a ORT viewing station, to optimize various kinds of image processing, and finally to establish the most effective image-processing on CRT diagnosis. The result of the interpretation of subtle pulmonary abnormalities on the ORT monitor showed that high frequency enhancement, was not necessary beneficial because the normal arteries often mimicked the abnormal interstitial shadows. Generally low frequency enhancement processing was better than high frequency enhancement In addition, the presence of subtle ground glass finding may be missed on a soft-copy image due to inadequate image processing resulting in blurred image, although detected on the conventional film image. The effect of image processing differs depending on the type and characteristic of abnormalities.Interobserver's difference was also found in the evaluation of the effect of image processing. Imaging diagnosis on CRT monitor has a merit of freely available image processing. However, diagnostic criterion and its process developed from conventional screen-film image are not necessary applied directly to-soft copy image. Especially, high frequency enhancement, processing often induces over- or underdiagnosis of chest image.