OBJECTIVETo explore the preoperative diagnostic value of MR diffusion weighted imaging (DWI) for metastatic lymph nodes in patients with gastric cancer.

METHODSBetween December 2011 and December 2012, 52 gastric cancer patients(34 men, 18 women) underwent preoperative MR DWI. The apparent diffusion coefficient(ADC) and short diameter of lymph nodes were measured and compared with the postoperative histopathological findings. Diagnostic value of ADC and short diameter for metastatic lymph nodes in patients with gastric cancer was investigated by receiver characteristic curve(ROC) analysis.

RESULTSA total of 180 metastatic and 57 non-metastatic lymph nodes were detected as hyperintense on DWI obtained from 52 patients. The ADC of metastatic lymph nodes [(1.059±0.196)×10(-3) mm(2)/s] was significantly lower than that of non-metastatic nodes [(1.402±0.285)×10(-3) mm(2)/s, P<0.001]. With ADC threshold of 1.189×10(-3) mm(2)/s, the sensitivity, specificity and area under the curve(AUC) were 78.9%, 72.8% and 0.840, respectively. The overall diagnostic accuracy of preoperative N staging of ADC was 75%(39/52). The short diameter of metastatic lymph nodes [(8.08±3.99) mm] was significantly longer than that of non-metastatic lymph nodes [(6.75±2.70) mm, P=0.005]. With short diameter threshold of 5.05 mm, the sensitivity, specificity and AUC were 88.3%, 29.8% and 0.602, respectively. The overall diagnostic accuracy of short diameter in preoperative N staging was 67.3%(35/52).

CONCLUSIONSMR DWI is a useful technique in diagnosing metastatic lymph nodes in patients with gastric cancer. ADC value and short diameter can be used as diagnostic criterion for the diagnosis of preoperative N staging.