To investigate the diagnostic value of 3.0T MR diffusion weighted imaging (DWI) in pelvic lymph node metastasis of rectal cancer.

The clinical data and the conventional MRI and DWI data of 53 patients with postoperative pathological-proved rectal cancer were retrospectively analyzed. The lymph nodes were divided into metastatic and non-metastatic lesions according to pathological finding. ADC values of metastatic and non-metastatic lymph nodes were measured respectively. Statistical analysis was done by SPSS 19.0 program software. ROC curve was drawn, and the cutoff value for metastatic lymph nodes detection was determined, the sensitivity, specificity and accuracy were calculated. A P value <0.05 was considered as statistically significant.

In all 116 lymph nodes, there were 47 metastatic lymph nodes and 69 non-metastatic lymph nodes. ADC values of metastatic and non-metastatic lymph nodes were (0.81±0.10)×10^-3 mm²/s and (1.06±0.13)×10^-3 mm²/s respectively, the ADC values of metastatic lymph nodes were significantly lower than that of non-metastatic lymph nodes, the difference was statistically significant (t=10.47, P<0.05). ROC curve analysis showed that the ADC value for the best critical point of diagnosis for metastatic lymph nodes was 0.95×10^-3 mm²/s. The sensitivity was 91.5%, specificity was 78.3%, accuracy was 83.6%.

The value of 3.0T MR DWI ADC has high diagnostic value in pelvic lymph node metastasis of rectal cancer, which can provide more information for treatment and prognostic evaluation.