Xu X W, Doi K
Kurt Rossmann Laboratories for Radiologic Image Research, Department of Radiology, University of Chicago, Illinois 60637, USA.
Med Phys. 1996 Sep;23(9):1613-24. doi: 10.1118/1.597738.
Diaphragm edges, together with ribcage edges, in chest radiographs provide useful information on the location, shape, and size of the lung fields that are required by computer-aided diagnosis (CAD) schemes for automated detection of various abnormalities. In this continued study, we developed a computerized method for detection of the right and left hemidiaphragm edges. First, the right hemidiaphragm edges in a PA (postero-anterior) chest image were determined by edge gradient analysis. An initial vertical ROI was then placed at the middle of the left hemidiaphragm, based on a "standard rule" for determination of the starting points to search for the left hemidiaphragm edges. Seven categories were used to assess the accuracy of the placement of the initial ROI and the selection of the primary left starting point within the initial ROI. For some categories, it was necessary to select a second left starting point besides the primary one. Therefore, for these categories, two sets of "detected left hemidiaphragm edges" resulted from the two left starting points. Two parameters were used as measures to eliminate the false left hemidiaphragm edges which were due to an incorrect left starting point. Two polynomial functions were applied separately which produced smooth curves for the right and left hemidiaphragm edges. Finally, the delineation of the lung field in a chest image was obtained by connecting the right and left hemidiaphragm edge curves with the corresponding ribcage edge curves. The subjective evaluation results indicated that the accuracy for the determination of the right and left hemidiaphragm edges was approximately 97% and 90%, respectively.
在胸部X光片中，膈肌边缘与胸廓边缘一起，为计算机辅助诊断（CAD）方案自动检测各种异常情况提供了有关肺野位置、形状和大小的有用信息。在这项后续研究中，我们开发了一种用于检测左右半膈肌边缘的计算机化方法。首先，通过边缘梯度分析确定后前位（PA）胸部图像中的右半膈肌边缘。然后，根据确定左半膈肌边缘搜索起始点的“标准规则”，在左半膈肌中部放置一个初始垂直感兴趣区域（ROI）。使用七种类别来评估初始ROI放置的准确性以及初始ROI内主要左起始点的选择。对于某些类别，除了主要起始点外，还需要选择第二个左起始点。因此，对于这些类别，从两个左起始点产生了两组“检测到的左半膈肌边缘”。使用两个参数作为度量来消除由于左起始点错误而产生的假左半膈肌边缘。分别应用两个多项式函数，为左右半膈肌边缘生成平滑曲线。最后，通过将左右半膈肌边缘曲线与相应的胸廓边缘曲线连接起来，获得胸部图像中肺野的轮廓。主观评估结果表明，左右半膈肌边缘确定的准确率分别约为97%和90%。
