多层螺旋CT肛缘定位的研究

The anal verge：localization with multi-slice spiral CT

目的确定与评价MSCT肛缘的解剖定位与测量方法，从而为中低位直肠癌手术术式的选择提供参考。方法从2009年8月始连续选取48例因怀疑其他疾病而行腹盆腔CT检查的成年患者，按性别或年龄进行分组。男性组23例，女性组25例；低年组24例患者28～50岁，平均41岁，高年组24例患者52～81岁，平均64岁。于患者肛缘处用浸有碘对比剂的棉球作标记后行64层螺旋CT扫描，于MPR法得到的矢状面图像上分别测量耻骨联合下缘到肛缘（棉球）的距离（La）、骶5椎体下缘到肛缘的距离（Lb）、小骨盆下口与肛缘的距离（Lc）、肛门外括约肌基底襻的下缘与棉球的距离（IA）。分别计算La、Lb、Lc与Ld的平均值、标准差（s）与95％、80％可信区间。以±1．96s或±1．28s的范围〈5mm为满足临床需要的标准。将满足标准的距离分别按照不同性别和年龄2组采用t检验进行比较。结果Ld值为（9．8±1．2）mm，其±1．96s和±1．28s分别为4．8mm和3．0mm，符合要求，且测量方便。男性组和女性组Ld分别为（10．0±1．2）和（9．6±1．2）mm，低年组和高年组Ld分别为（9．6±1．2）和（9．9±1．3）mm，差异均无统计学意义（P〉0．05）。结论肛门外括约肌基底襻下缘在MSCT上可清楚显示，其与肛缘之间的距离恒定，且测量方便，将其作为CT图像上直肠肿瘤与肛缘距离测量的解剖标志，误差可在0．5cm以内。

Objective To determine and evaluate the method of localization of anal verge by muti- slice spiral CT. To provide an imaging reference for operative guidance of low-rectal cancer. Methods Forty eight consecutive adult patients suspected of abnormalities other than rectal disease were evaluated with abdominal and pelvic CT scans since August, 2009. They were divided into two groups based on sex and age. There were 23 men and 25 women. The ages of young group were 28 to 50 years and the average age was 41 years. The ages of elderly group were 52 to 81 years and the average age was 64 years. A small cotton ball dipped with contrast media was put at the anal verge as a marker and CT scans were performed with 64-slice spiral CT scanner. The distances between the cotton balls and the lower margin of the pubis combination （La）, the lower margin of the 5th sacral vertebra （Lb）, the inferior aperture of minor pelvis （Lc） and the lower margin of the basement of external anal sphincter （Ld） were measured on the midsagittal images obtained by MPR. The averages, the standard deviations（ s）, the 95% and 80% confidence intervals of La, Lb, Lc and Ld were calculated. We took the intervals of ± 1.96 s or ± 1.28 s 〈 5 mm as the standard of meeting the clinical requirement. The distances meeting the clinical requirement between different sex groups or age groups were compared with t test. Results The Ld was （9. 8 ± 1. 2） mm, of which intervals of ± 1.96 s and ± 1.28 s were 4. 8 mm and 3.0 mm respectively, meeting the clinical need. This distance was also measured conveniently. There were no significant differences （ P 〉 0. 05） between two different sex groups [ male group, （ 10. 0 ±1.2） mm], female group, （9. 6 ± 1.2） mm and between two age groups [ young group, （9. 6 ± 1.2） mm, elderly group, （9.9 ± 1.3 ） mm ]. Conclusions The lower margin of the basement of external anal sphincter was a useful anatomic lanmark for localizing the anal verge, and could be definitely identified on the middle sagittal pelvic CT image. The distance between the structure and anal verge is constant enough and can be used in measuring distance from low rectal lesion to the anal verge.