Pseudolesion of the bile duct caused by flow effect: a diagnostic pitfall of MR cholangiopancreatography

Abstract

Objective: Our objective was to examine the influence of the shape of imaged structures and the velocity of flow on the appearance of flow artifacts seen on MR cholangiopancreatography (MRCP) in a phantom model.

Materials and methods: Three types of phantoms representing the biliary system were constructed. The first phantom type was a straight tube; the second, a single tube in which the inlet and outlet diameters varied by a ratio of as much as 1:6; and the third, a tube that simulated a stricture in the biliary system and a gallstone. All experiments were repeated three times.

Results: We did not observe any flow artifacts in the experiments we performed with the straight tubes. A higher rate of flow resulted in decreased signal intensity in tubes simulating bile ducts; the decreased signal was most likely to be observed on images in which the speed of flow exceeded 5 mm/sec. Flow artifacts were seen only if the ratio between the inlet and outlet diameters was 1:4 or greater. Simulations of bile duct abnormalities--such as a 50% stricture or the presence of a gallstone--did not produce any flow artifacts.

Conclusion: In our experiments, a flow artifact could be seen on images in which the ratio between the inlet and the outlet diameters in the phantom was equal to or greater than 1:4. This finding indicates that a flow artifact could be observed in dilated bile ducts on MRCP under clinical conditions. Knowing that a pseudo-filling defect can be caused by a flow artifact should help to prevent misinterpretation of MRCP images.