MRI在直肠癌术前评价中的价值已得到国际的公认。由于全直肠系膜切除（TME）是基于盆腔局部解剖基础提出的手术方法，在术前应用MRI成像清晰显示TME相关解剖结构和变异及其与肿瘤的关系，并能够正确识别和掌握与TME相关的MRI征象将有助于外科医生在术前更全面了解病变情况。文章从影像学角度对TME相关解剖的MR显示及其征象，直肠癌MR术前分期，环周切缘的术前判定及直肠MR成像技术4个方面做一系统的阐述和总结，以期对外科医生应用和掌握直肠癌术前MR检查有所帮助。

Preoperative MRI evaluation of low rectal cancer in the total mesorectal excision ZHANG Xiao-peng,SUN Ying-shi. Medical Imaging Division, Peking University Institute of Clinical Oncology,Beijing Cancer Hospital and Beijing Institute for Cancer Prevention,Beijing100142,China Corresponding author: ZHANG Xiao-peng,E-mail:zxpabc@263.net Abstract The value of MRI in the preoperative evaluation of rectal cancer has been recognized internationally. As a result of total mesorectal excision (Total Mesorectal Excision, TME) is based on the anatomical basis of pelvic regional anatomy, the application of MRI in preoperative imaging clearly indicate that anatomical structure and its variation related to TME as well as its relationship with the tumor. We can correctly identify and grasp the TME-related MRI signs which will help the surgeon realize the lesions well before the operation. This article from the perspective of TME relevant anatomy imaging and MR signs, preoperative MR staging of rectal cancer, the preoperative judgement of circumferential resection margin and MR imaging technology to make a systematic elaboration and conclusion, with a view to help the surgeon apply and master preoperative MR rectal examination.