Abstract: Abstract：Objective To study the application value of conventional MRI combined with DWI and DCE-MRI in differentiating benign and malignant regional lymph nodes of rectal cancer. Methods Preoperative MRI data of 65 patients with rectal cancer confirmed by operation and pathology were retrospectively analyzed. The accuracy of conventional MRI and conventional MRI plus DWI and DCE-MRI examination were analyzed in the diagnosis of benign and malignant lymph nodes， which was consistent with the postoperative pathology. The correlation of time-intensity curve (TIC) types， apparent diffusion coefficient (ADC) values and Ktrans ， Ve， Kep values with benign and malignant lymph nodes were also analyzed. Results The total diagnostic accuracy rate of conventional MRI for benign and malignant lymph nodes was 67.7% (317/ 468). The total diagnostic accuracy rate of conventional MRI plus DWI and DCE-MRI for benign and malignant lymph nodes was 78.2% (366/468). The benign lymph nodes were dominated by type I curve. The malignant lymph nodes were dominated by type Ⅲ curve. Ktrans ， Ve and Kep values were higher in metastatic lymph nodes than those of benign lymph nodes, and ADC values were lower than benign lymph nodes (P＜0.05). Conclusion Conventional MRI combined with DWI and DCE-MRI can improve the detection rate of regional malignant lymph nodes in rectal cancer. TIC types, ADC values and Ktrans ， Ve and K values have certain application value in differentiating benign and malignant regional lymph nodes of rectal cancer.

Key words: rectal neoplasms, lymph nodes, magnetic resonance imaging, diffusion weighted imaging, dynamic contrast-enhanced magnetic resonance imaging