下段直肠及肛管CT轴位图像测量方法的研究

目的:研究直肠肛管的轴位CT测量方法。材料与方法:84例标记肛门的盆腔增强CT检查,其中15例同时行结肠气钡双对比检查。测量并计算直肠壶腹距肛门的实际长度与其层面距离的比值,同时在CT及气钡双对比造影图像上测量肛门距坐骨结节下缘平面的垂直距离、肛管长度及肛直角。用SPSS 11.5软件对数据进行统计分析。结果:在横轴位CT图像上,肛管由环行变为开口向后的U形时,即为肛门所在位置。CT与钡灌肠两种方法测量肛门距坐骨结节下缘平面距离、肛管长度及肛直角,差异无统计学意义。通过CT测量的直肠壶腹距肛门的实际长度与相应层面距离的比值均值为1.3。结论:CT图像可以清楚显示肛门及肛管,下段直肠距肛门的CT层面距离与实际长度间存在差异,通过本研究提出的比值法可以较准确的在轴位CT上测量下段直肠距肛门长度。

A study of the measuring method for lower rectum and anal canal with axial CT

Objective: To evaluate the method of rectum and anal measurement with axial CT. Material and Method: Eighty-four cases with CT study of pelvis were included,and 15 of them took double-contrast barium enema. The anus was marked before the study. The length from protruding of rectal ampullae to anus to its slice distance was measured and calculated. Length of anal canal,anorectal angle and the slice distance from anus to the plane through two ischial tuberosities were measured on both CT and double-contrast barium images. The data of result were analyzed with SPSS 11.5 software. Result: The anus could be localized where the shape of the anal canal transformed from ring-like to U-shaped opening posteriorly. There was no significant difference between CT and double-contrast barium in respect to the distance from anus to the plane through two ischial tuberosities,length of anal canal and anorectal angle. The ratio of length to slice distance from rectal ampullae to anus was 1.3 calculated from CT. Conclusion: The anal canal and anus can be observed on CT images. There is difference between the distance from lower rectum to anus out of counting the number of the image slices and the actual length. With the ratio method introduced in our study,the length from low rectum to anus can be measured rather accurately with axial CT images.