Abstract：Objective: To assess the role of adding T1WI to MR cholangiopancreatography in detecting micro-choledocholithiasis. Materials and Methods: A total 104 patients having choledocholithiasis from January 2005 to December 2006 were preoperatively performed by routine MRI and MRCP. Less than 5mm micro-stones of the common bile ducts were proved by surgery or ERCP following MRI scan by 1~5 days in 56/104 patients. Routine MRI scan included RF-FAST axial T1WI(TR/TE 155ms/3.4ms) and axial fast T2WI(TR/TE 15000ms/81ms) as well as coronal T2WI(TR/TE 15000ms/81ms). EXPRESS fat-saturation imaging sequences of MRCP set included five 45mm thick-sections in oblique coronal planes in the course of the bile duct and 5mm thick no-gap coronal images(source images). Maximum intensity projection(MIP) images were generated from the coronal source images. Features of common bile duct micro-calculi on T1WI and MRCP images and the sensitivities of T1WI and MRCP diagnosing for common bile duct micro-stones were analyzed. Results: Of these 56 patients, gallbladder stones were coexisted with choledocholithiasis in 30 patients and in whom 7 patients had a history records of cholecystectomy for gallstones. The signal intensities of common bile duct micro-calculi on T1WI were high relative to the low signal intensity of the bile in 47 patients. Filling-defects of hypo-intensity signals on MRCP images were shown in 33 patients. Both T1WI and combination MRCP with T1WI had a high sensitivity in detecting the common bile duct micro-calculi than MRCP alone. Statistics showed significant differences in detecting micro-stones between combination MRCP with T1WI and MRCP alone(Fisher exact test, P<0.01). Conclusion: Adding T1WI to MRCP will be helpful to provide a significant high sensitivity for diagnosing micro-calculi of the common bile ducts.
2007, Vol. 18 
