Pancreatic ductal adenocarcinoma: Prevalence and diagnostic value of dark choledochal ring sign on T2-weighted MRI

Abstract

To investigate the dark choledochal ring sign on T2-weighted imaging (T2WI) as an indicator for pancreatic ductal adenocarcinoma (PDAC) among periampullary carcinomas. Sixty patients with surgically confirmed periampullary cancers [30 PDACs, 15 distal common bile duct (CBD) cancers, 13 ampullary cancers, and two duodenal cancers] who underwent liver magnetic resonance imaging (MRI) were included in this study. Two reviewers independently evaluated unenhanced and gadoxetic acid-enhanced MRI (T1WI image set), and a combined T2WI and T1WI image set for differentiation between PDAC and other periampullary carcinomas using a rating scale, and the presence of the dark choledochal ring sign on T2WI, for all 60 tumours. In PDAC, the dark choledochal ring sign on T2WI was considered positive in 23 cases by observer 1 and 24 cases by observer 2, but only in one or two CBD cancers, as determined by each observer, respectively. This resulted in sensitivities of 76.7% and 80% and specificities of 96.7% and 93.3% for observer 1 and 2, respectively, in the diagnosis of PDAC. Adding T2WI correctly led to a change of diagnosis in three and four cases of PDAC by each observer, respectively. Thus, there were significant differences between the two image sets for both observers in distinguishing between PDAC and other periampullary carcinomas (p=0.02). The presence of the dark choledochal ring sign on axial T2WI could be a complementary imaging feature indicative of PDAC to differentiate PDAC from other periampullary carcinomas at MRI.