The role of combining MR cholangiopancreatography and T1W imaging in detecting common bile duct micro-stones

Abstract Objective: To assess the role of adding T1W images to MR cholangiopancreatography (MRCP) in detecting common bile duct (CBD) micro-stones. Subjects and Methods: From January 2005 to December 2006, a total of 104 patients with CBD stones were preoperatively studied by routine MRI and MRCP. Micro-stones, measuring less than 5 mm, were proven at surgery or ERCP following the MRI scans, within one to five days in 56/104 patients. Routine MRI scans included RF-FAST axial T1W images (TR/TE 155 ms/3.4 ms) and EXPRESS axial T2W (15000 ms/81 ms) as well as coronal T2W (15000 ms/81 ms) images. Features of CBD micro-calculi on T1W and MRCP images and the sensitivities of T1W images and MRCP for the diagnosis of CBD micro-stones were analyzed. Results: Among these 56 patients, gallbladder stones coexisted with choledocholithiasis in 30 patients and 7 patients had a past history of cholecystectomy for gallstones. The signal intensities of CBD micro-calculi on T1W images were high, relative to the low signal intensity of the bile in 47 patients. Filling defects on MRCP images were shown in 33 patients. Both T1W images alone and a combination of MRCP with T1W images had a higher sensitivity in detecting CBD micro-calculi than MRCP alone. Statistical analysis showed significant differences between the combination of MRCP with T1W images and MRCP alone in the ability to detect micro-stones (Fisher′s exact test, P < 0.01). Conclusion: For MRCP, adding a T1W sequence is helpful in increasing the sensitivity for diagnosing micro-calculi of the common bile ducts.