Value of diffusion-weighted MR imaging in the diagnosis of lymph node metastases in patients with cholangiocarcinoma

Purpose To evaluate diffusion-weighted MR imaging (DWI) in the diagnosis of lymph node metastases in patients with cholangiocarcinoma. Methods In 24 patients with cholangiocarcinoma, MR imaging of the upper abdomen was performed prior to surgery at 1.5 T using a respiratory-triggered single-shot echo-planar imaging (SSEPI) sequence ( b values: 50, 300, and 600 s/mm 2 ). ADC (apparent diffusion coefficient) values and diameters of regional lymph nodes (LN) were determined. Subsequently, in all patients, surgical exploration and/or resection of the primary tumor and regional LN dissection were performed. Imaging results were correlated with results of histopathologic analysis. ADC values and diameters of benign and malignant LN were compared using the Mann–Whitney U test. In addition, a ROC (receiver operating characteristic curve) analysis was performed. Results The mean ADC value (×10 −3 mm 2 /s) of metastatic LN (1.21 ± 0.15) was significantly lower than that of benign LN (1.62 ± 0.33, p < 0.001) while there was no significant difference in the mean diameter of malignant (16.8 ± 5.4 mm) and benign LN (14.1 ± 4.0 mm; p = 0.09). Using an ADC value of 1.25 × 10 −3 mm 2 /s as threshold, 91.4% of LN were correctly classified as benign or malignant with a sensitivity/specificity of 83.3%/92.8% and a positive/negative predictive value of 66.7%/96.7%. The area under the ROC curve was 0.93. Conclusion DWI using a respiratory-triggered SSEPI sequence, according to our preliminary experience, is a promising imaging modality in the differentiation of benign and malignant LN in patients with cholangiocarcinoma.