Li Q, Katsuragawa S, Ishida T, Yoshida H, Tsukuda S, MacMahon H, Doi K
Department of Radiology, The University of Chicago, Illinois 60637, USA.
Med Phys. 2000 Jan;27(1):47-55. doi: 10.1118/1.598856.
A novel contralateral subtraction technique has been developed to assist radiologists in the detection of asymmetric abnormalities on a single chest radiograph. With this method, the lateral inclination is first corrected by rotating and shifting the original chest image so that the midline of the thorax is aligned with the vertical centerline of the original chest image. The rotated image is then flipped laterally to produce a reversed "mirror" image. Finally, the mirror image is warped and subtracted from the original image for derivation of the contralateral subtraction image. The three key techniques which are employed in this study are applied successively to the initial contralateral subtraction technique for acquisition of improved subtraction images. One hundred PA chest radiographs, including 50 normals and 50 abnormals, were used as the database for this study. The percentage of chest images, which were rated as being adequate, good, or excellent quality of subtraction images by employing a subjective evaluation method, was improved from 73% to 91% by use of the three key techniques. The contralateral subtraction technique can be used for detection of any asymmetric abnormalities, such as lung nodules, pneumothorax, pneumonia, and emphysema, on a single chest radiograph, and therefore has potential utility in a high proportion of abnormal cases.
一种新型的对侧减法技术已被开发出来，以帮助放射科医生在单张胸部X光片上检测不对称异常。使用这种方法时，首先通过旋转和移动原始胸部图像来校正侧倾，使胸部中线与原始胸部图像的垂直中心线对齐。然后将旋转后的图像进行横向翻转，以生成一个反向的“镜像”图像。最后，将镜像图像进行变形并从原始图像中减去，以获得对侧减法图像。本研究中采用的三项关键技术依次应用于初始对侧减法技术，以获取改进后的减法图像。100张后前位胸部X光片，包括50张正常片和50张异常片，被用作本研究的数据库。通过使用这三项关键技术，采用主观评估方法评定为减法图像质量足够、良好或优秀的胸部图像百分比从73%提高到了91%。对侧减法技术可用于在单张胸部X光片上检测任何不对称异常，如肺结节、气胸、肺炎和肺气肿，因此在很大比例的异常病例中具有潜在应用价值。
