目的 :研究肿瘤内部MR表观弥散系数 (apparentdiffusionco efficient,ADC)预测原发性直肠癌术前联合放化疗敏感性的价值。方法 :16例经组织学证实的原发性直肠癌 (cT3 )患者 ,在开始术前标准联合放化疗前行MRI检查。采用 1.5T弥散加权自旋回波平面成像 (SE EPI)和T1加权增强自 Objective: To study the value of MR apparent diffusion coefficient (apparent diffusion coefficient, ADC) in predicting the preoperative chemoradiotherapy sensitivity of primary rectal cancer. METHODS: Twenty-six patients with histologically-proven primary rectal cancer (cT3) underwent MRI prior to standard preoperative chemoradiation. 1.5T diffusion weighted spin echo planar imaging (SE EPI) and T1 weighted self-enhancement