OBJECTIVETo evaluate the diagnostic value of 3.0 T diffusion-weighted imaging with background suppression (DWIBS) magnetic resonance (MR) for lymph node metastasis in rectal cancer.

METHODSThirty-five patients with rectal cancer who underwent preoperative routine MRI+DWI examination were enrolled in the study and were treated by rectal cancer resection plus lymph node dissection. Metastatic and non-metastatic lymph nodes were confirmed by postoperative pathology. Apparent diffusion coefficient (ADC) values, long-axis and short-axis diameters of lymph nodes were measured. Receiver operating characteristic (ROC) curve was used to assess the diagnostic efficacy of ADC, long-axis and short-axis diameters for differentiating metastatic lymph nodes from non-metastatic lymph nodes.

RESULTSA total of 151 lymph nodes were confirmed with exact location in 35 patients. Sixty-five metastatic lymph nodes and 86 non-metastatic lymph nodes were identified. The ADC values of metastatic lymph nodes and non-metastatic lymph nodes were(0.86±0.14)×10(-3) and (0.94±0.16)×10(-3) mm(2)/s respectively. The long-axis diameter were(9.78±3.13) and (7.90±1.77) mm, respectively. The short-axis diameter were (7.65±2.00) and (6.45±1.19) mm, respectively. There were statistically significant differences between metastatic and non-metastatic lymph nodes in ADC values, long-axis diameter, and short-axis diameter(all P<0.01). The areas under the ROC curve of ADC value, long-axis diameter, and short-axis diameter were 0.648, 0.706, and 0.692, respectively. Optimal cutoff values for these parameters were 1.05×10(-3) mm(2)/s, 7.95 mm, and 5.90 mm, respectively, and the corresponding sensitivities and specificities were 93.8% and 30.2%, 75.4% and 61.6%, 90.8% and 38.4%.

CONCLUSIONSQuantitative measurement of ADC value may reflect the degree of diffusion restriction of metastatic lymph nodes by DWIBS at 3.0 T MR. Accurate diagnosis of metastatic lymph nodes in rectal cancer demands comprehensive evaluation combining ADC value with diameter measurement.