直肠癌是我国常见的恶性肿瘤之一。由于直肠癌位置的特殊性，使得治疗方案的选择除了考虑预后与生存期的问题，还需要兼顾是否保肛或性功能损伤等一系列影响生活质量的问题，而淋巴结性质是影响治疗方案选择的关键因素之一。MRI是直肠癌疗前评估的推荐检查方法，但多年来其对淋巴结的评价缺乏统一的标准，淋巴结分期的准确性不高且徘徊不前，制约了直肠癌个体化治疗的发展。. 本课题拟通过将全系膜切除术后的完整标本进行MRI检查和保持解剖信息的病理大切片制作，在技术上实现术前MRI显示的淋巴结与病理收获淋巴结一一对应的前提下，从淋巴结自身病理生理学特征（如前期研究发现的化学位移效应等征象）以及数据提取与分析入手，使形态影像学、病理组织学与高通量数据特征充分融合，应用合理的选择算法和分类器，以期构建有效且方便临床转化应用的诊断模型，提高MRI对直肠癌淋巴结评估的准确性，从而更有效地指导临床治疗。

Rectal cancer is one of the most common malignancies worldwide. The favorable survival is crucial for determining the therapeutic strategy, besides, the factors influencing the quality of life, such as permanent enterostomy or sexual dysfunction, should also be considered in the clinical practice. Lymph node status constitutes one of the most important factors for selection of treatment scheme in patients with rectal cancers. Magnetic resonance imaging (MRI) is recommended as the standard technique for evaluation of primary rectal cancer before treatment. It is invaluable for evaluation of the tumor depth, circumferential resection margin and mesorectal vascular invasion, which are the risk factors for local recurrence. The evaluation of lymph nodal status, however, remains a daunting task. No uniform criteria exist for defining node-positive status. . In this study, the specimen after standard total mesorectal excision will be imaged again by MR with the same protocols as preoperative MRI. And then, each specimen will be sliced transversely to produce the whole-mount sections for precise node-for-node comparisons with in vivo and ex vivo MRI. A series of MR characteristics of lymph node including chemical shift effect, which has been reported by our team to be with significant difference between benign and metastastic lymph nodes, as well as histopathological information and high-throughput data character, will be utilized by algorithm analysis for construction of prediction models for lymph nodal status in rectal cancer.