3T Diffusion Weighted MR Imaging in Diagnosing Extrahepatic Cholangiocarcinoma

Objectives: To evaluate the incremental value of diffusion weighted imaging (DWI) in addition to magnetic resonance cholangiopancreat-ography (MRCP) in diagnosing extrahepatic cholangiocarcinoma (EHCC); to determine the most appropriate b value for DWI on 3.0 T MRI. Methods: Preoperative MRI examinations were performed for 63 patients with suspected EHCC. The examinations included T2-weighted imaging, coronal fast imaging employing steady-state acquisition (FIESTA), MRCP and DWI sequence with different b values (500, 1000 and 1200s/mm2). All cases were confirmed by histopathological diagnosis. Two radiologists in consensus reviewed MRCP imaging and combined MRCP and DWI imaging with ADC maps, and apparent diffusion coefficient (ADC) value, signal-noise ratio (SNR), contrast-to-noise ratio (CNR) and signalintensity ratio (SIR) under various b values were calculated. Results: There were significant differences in sensitivity (74.4% vs. 94.9%), specificity (75% vs. 100%) and accuracy (74.6% vs. 96.8%) between MRCP alone and combined MRCP and DWI with a b value of 1000 s/mm2 (P<0.05). There was also a significant difference in ADC, SNR, CNR and SIR under various b values (P<0.05). Conclusion: For diagnosing EHCC, the combined use of MRCP and DWI shows a better diagnostic performance than MRCP alone; the b value of 1000 s/mm2 is the most appropriate for DWI on 3.0T MRI.