High-resolution MR cholangiopancreatography.
Watanabe Y. Dohke M. Ishimori T. Amoh Y. Oda K. Okumura A. Mitsudo K. Dodo Y.
Department of Radiology, Kurashiki Central Hospital, Japan.
1. High-resolution MRCP is a noninvasive imaging modality for depicting the pancreatobiliary tree. The imaging quality of high-resolution MRCP is satisfactory. MRCP can demonstrate dilation, stenosis, and intraductal filling defects of both the biliary tract and the pancreatic duct, which meets the clinical demand for pancreatobiliary imaging. 2. MRCP was successful in almost all the patients. However, the causes of MRCP failure were patient motion, irregular respiratory rhythm, severe pneumobilia, and massive ascitic fluid. 3. When only MIP reconstructed images were used for interpretation, small intraductal filling defects such as a gallstone can be missed. In combination with coronal source images, the ability to detect intraductal stones can be increased. 4. Ferrite ammonium citrate (FAC) is useful in suppressing the background signal intensity of gastrointestinal contents so that the ducts can be clearly visualized. The other technique for decreasing the background signal intensity is target MIP postprocessing, which works well for better visualization of the ducts. 5. The degree of ductal narrowing tends to be overestimated with MRCP because of MIP reconstruction artifact and lower spatial resolution of MRCP than ERCP. 6. MRCP has a diagnostic pitfall of a pseudostenosis of extrahepatic ducts, which may lead to a false-positive diagnosis of ductal narrowing. This pitfall may be caused not only by MIP postprocessing artifacts but by gas, surgical metal, and vascular compression of right hepatic artery. There is another diagnostic pitfall that it is difficult to differentiate intraductal mucin from pancreatic fluid in dilate pancreatic ducts, although ERCP identifies mucin as intraductal filling defects.