Free breathing magnetic resonance cholangiopancreatography (MRCP) at end expiration: a new technique to expand clinical application

Abstract

Background/aims: To develop a new magnetic resonance cholangiopancreatography technique for patients who cannot hold their breath or breathe regularly and fail to be successfully examined with conventional magnetic resonance cholangiopancreatography methods.

Methodology: Within a one-year period, 15 patients including 6 children and 9 adults were studied. Magnetic resonance cholangiopancreatography was performed in a 1.5 Tesla GE MR scanner with capability of single-shot fast spin echo sequence. In all patients except for the children, magnetic resonance cholangiopancreatography was attempted with the breathhold technique at first. However, this failed in some due either to the patients being too old or too weak to hold their breath long enough for single-shot fast spin echo sequence, which usually took about 20-30 seconds for the complete scanning. These 15 cases were then scanned slice-by-slice in operator's control mode by monitoring patient's respiratory pattern from the TV monitor. Scanning was started near the end of patient's expiration. This technique was performed after we had carefully decided the baseline of each patient's respiration cycle. Each slice was scanned at an interval depending on the patient's respiratory frequency. It was acquired at an interval of two respiratory cycles for each sequential slice when the patient's respiration frequency was around 10-15 cycles per minute, at three cycles when respiration frequency was around 15-20, at four cycles when the frequency was around 20-25, and at an interval of 5 cycles when it was above 25. The acquired source images were then reconstructed for a 3D image.

Results: Magnetic resonance cholangiopancreatography of good image quality was obtained in all of these fifteen patients. Each set of images took about 2-3 minutes. No marked artifact was found. The reconstructed 3D image also afforded satisfactory quality for evaluation of both normal ductal anatomy and lesions of the biliary-pancreatic system. The axial single-shot fast spin echo sequence images of the liver and pancreas were also successfully obtained with this method. Magnetic resonance cholangiopancreatography findings in these 15 patients included type I choledochal cyst (n = 4), dilatation of the intrahepatic bile ducts due to mass compression (n = 3, one Klatskin tumor and two hilar masses), pancreatic carcinoma (n = 1), acute cholecystitis without biliary tract dilatation (n = 1), acute pancreatitis with mild biliary dilatation and non-visible pancreatic duct (n = 1), dilatation of biliary tract without definite lesions (n = 2), common hepatic duct obstruction (n = 1), and normal biliary and pancreatic duct without dilatation or lesions (n = 2).

Conclusions: Free breathing magnetic resonance cholangiopancreatography technique is very useful for patients in whom conventional methods cannot be successfully undertaken. It affords informative images that are comparable to other magnetic resonance methods.