MR cholangiopancreatography: techniques and clinical applications

Comparison of endoscopic retrograde cholangiopancreatography with MR cholangiopancreatography in patients with pancreatitis

PURPOSE

To assess the usefulness of magnetic resonance (MR) cholangiopancreatography (MRCP) in the evaluation of disease in patients with acute or chronic pancreatitis.

MATERIALS AND METHODS

MR imaging was performed at 1.5 T in 39 patients with chronic (n = 30) or acute (n = 9) pancreatitis. The patients underwent a pancreas MR imaging protocol that included an MRCP sequence. Comparison was made with findings at endoscopic retrograde cholangiopancreatography (ERCP), performed within 30 days. Three blinded readers used a scoring system to evaluate nine segments of the pancreatic and biliary ducts as depicted on the ERCP and MRCP images. MRCP image quality was also evaluated.

RESULTS

Of 196 segments analyzed, 17 were not seen at MRCP (sensitivity, 91%). Of the segments visualized at MRCP, 14 were incorrectly characterized (accuracy, 92%). At MRCP, segments not detected or mischaracterized were either normal, slightly dilated, or narrowed. At ERCP, 42 segments in 19 patients were not visualized. MRCP findings were considered useful in all those cases. MRCP image quality was not interpretable in two cases due to artifacts.

CONCLUSION

Very good correlation between ERCP and MRCP findings was demonstrated. Both modalities failed to depict pathologic conditions depicted by the alternative method. MRCP may obviate ERCP, particularly in patients who cannot undergo ERCP or in whom ERCP has been unsuccessful.

Diagnostic pitfalls of MR cholangiopancreatography in the evaluation of the biliary tract and gallbladder

Magnetic resonance (MR) cholangiopancreatography is a noninvasive imaging technique that has proved accurate in the diagnosis of biliary obstruction. However, various diagnostic pitfalls have been reported with MR cholangiopancreatography that were not encountered previously at conventional biliary imaging. These pitfalls may simulate or mask various pathologic conditions of the extrahepatic bile duct or main pancreatic duct and may be caused by a variety of factors. Because of its postprocessing nature, maximum-intensity-projection reconstruction may mask a small gallstone if the stone is surrounded by hyperintense bile and may cause false ductal disconnection or duplication when a breath hold is not performed perfectly. Extraductal factors (e.g., metallic surgical clips, intravascular metallic coils, gas in the stomach or duodenum) can cause signal loss in the adjacent part of the extrahepatic bile duct, which may in turn lead to a false-positive diagnosis of ductal narrowing or obstruction. Normal vascular structures including the right hepatic and gastroduodenal arteries can cause pseudo-obstruction of the extrahepatic bile duct by pulsatile compression. Intraductal factors (e.g., gas, hemorrhage, debris, iodinated contrast material) reduce the signal intensity of the bile, which may result in pseudo-obstruction, false filling defects, or a nonvisualized gallbladder or bile duct. Knowledge of the existence and high prevalence of these diagnostic pitfalls should help prevent misinterpretation of MR cholangiopancreatograms.

HASTE MR cholangiopancreatography in the evaluation of intraductal papillary-mucinous tumors of the pancreas

PURPOSE

The aim of this study was to determine the usefulness of MR cholangiopancreatography (MRCP) of intraductal papillary-mucinous tumors.

METHOD

Thirteen patients with intraductal papillary-mucinous tumors were examined by breath-hold MRCP using a half-Fourier acquisition single-shot turbo spin echo (HASTE) sequence with a body phased-array coil.

RESULTS

Endoscopic retrograde cholangiopancreatography (ERCP) and MRCP completely imaged the entire main pancreatic duct in 12 and in all 13 patients, respectively. ERCP demonstrated the whole opacification of the cystic lesion in only one patient. MRCP depicted the whole of the cystic lesion in all 11 patients who had cystic lesions. ERCP and MRCP source images depicted a communicating duct between the main pancreatic duct and the cystic lesion in 8 and in all 11 patients, respectively. ERCP depicted papillary projections in the main pancreatic ducts in two patients. MRCP source images depicted papillary projections in the main pancreatic ducts or cystic lesions in five patients.

CONCLUSION

MRCP may be more useful to reveal the main pancreatic duct, cystic lesion, communicating duct between the main pancreatic duct and cystic lesion, and papillary projections than ERCP in patients with intraductal papillary-mucinous tumors of the pancreas.

Magnetic resonance cholangiopancreatography

Magnetic resonance cholangiopancreatography (MRCP) uses MR imaging to visualize fluid in the biliary and pancreatic ducts as high signal intensity on T2-weighted sequences; it is the newest modality for biliary and pancreatic duct imaging. MRCP is of proven utility in a variety of biliary and pancreatic diseases, including choledocholithiasis, congenital anatomic variants, chronic pancreatitis, post-cholecystectomy disorders, and neoplastic duct obstruction. MRCP is an evolving technique, but it has reached the stage of development where it is clinically useful and of comparable accuracy to conventional cholangiography. With further progress, it is likely that by the start of the new millennium MRCP will replace diagnostic endoscopic retrograde cholangiopancreatography as the modality of choice for imaging the biliary and pancreatic ducts.

Mangafodipir trisodium: effects on T2- and T1-weighted MR cholangiography

The purpose of this study was to determine the effects of mangafodipir trisodium on heavily T2-weighted magnetic resonance cholangiography (MRC) images and on functional T1-weighted MRC. Pre- and post-mangafodipir trisodium heavily T2-weighted MRC and fat-suppressed T1-weighted three-dimensional (3D) gradient-echo MRC images were obtained in a patient with a prior cholecystectomy and a long cystic duct remnant that had apparent biliary stasis. Multiplanar reconstructed images were created. The precontrast T2-weighted MRC showed a long cystic duct remnant and a normal common bile duct (CBD). The postcontrast T2-weighted MRC showed loss of CBD signal, but persistent signal in the cystic duct remnant due to biliary stasis. Post-mangafodipir T1-weighted 3D gradient-echo images showed the main right and left hepatic ducts, but the cystic duct was not depicted. Conventional T2-weighted MRC sequences should not be obtained after administering mangafodipir trisodium because this contrast agent decreases the T2 and therefore the signal intensity of bile within normally functioning bile ducts. Functional MRC images can be acquired by using a post-mangafodipir T1-weighted technique.

MR cholangiography: technical advances and clinical applications

Magnetic resonance (MR) cholangiography is a fast, accurate, noninvasive alternative to endoscopic retrograde cholangiography (ERC) in the evaluation of biliary tract disease. Technical improvements in imaging sequences (eg, half-Fourier rapid acquisition with relaxation enhancement) and use of phased-array coils allow high-quality imaging comparable to that available with ERC. In choledocholithiasis, common bile duct stones as small as 2 mm can be detected with MR cholangiography and appear as low-signal-intensity foci within the high-signal-intensity bile. MR cholangiography may help establish the diagnosis of malignant obstruction and is useful in the evaluation of patients in whom ERC was unsuccessful or incomplete. The role of MR cholangiography in the evaluation of intrahepatic duct disease continues to evolve. MR cholangiography plays a crucial role in evaluating postsurgical biliary tract alterations and can be used to demonstrate a variety of congenital anomalies of the biliary tract (eg, aberrant ducts, choledochal cysts, pancreas divisum). In addition, intentional or incidental imaging of the gallbladder with MR cholangiography can be used to identify calculi or help determine the presence and extent of neoplastic disease.

MR pancreatography: a useful tool for evaluating pancreatic disorders

Magnetic resonance (MR) pancreatography is being used with increasing frequency as a noninvasive alternative to diagnostic endoscopic retrograde pancreatography in the evaluation of the pancreatic duct and various pathologic conditions of the pancreas. This recently developed technique allows improved spatial resolution and permits imaging of the entire pancreatico-biliary tract during a single breath hold. MR pancreatography can help identify the course and drainage pattern of the pancreatic duct and is useful in diagnosing congenital anomalies such as pancreas divisum and annular pancreas without the risk of inducing pancreatitis. In some instances, MR pancreatography may demonstrate duct disruption and associated fluid collections resulting from trauma. In recurrent acute pancreatitis, MR pancreatography is useful in suggesting the cause of the disease; in chronic pancreatitis, it is useful in depicting ductal anatomy, detecting strictures or intraductal calculi prior to surgery, and detecting complications such as pseudocysts and fistulas. In addition, MR pancreatography performed in conjunction with abdominal MR imaging is useful in identifying pancreatic malignancies as well as in establishing resectability and preventing unnecessary preoperative stent placement.

MR cholangiopancreatography of pancreaticobiliary diseases: comparing single-shot RARE and multislice HASTE sequences

OBJECTIVE

In this study, we compared the single-shot rapid acquisition with relaxation enhancement (RARE) sequence with the multislice half-Fourier acquisition single-shot turbo spin-echo (HASTE) sequence to assess the ability of each technique to show various pancreaticobiliary diseases using MR cholangiopancreatography.

SUBJECTS AND METHODS

MR cholangiopancreatography was performed using both the single-shot RARE and the multislice HASTE pulse sequences in 80 consecutive subjects in whom we had proof of a range of diagnoses. The study population included healthy subjects (n = 9), patients with benign lesions (n = 41), and patients with malignant lesions (n = 30). We analyzed each image using the following criteria: the cause of the lesions, the image quality (i.e., the amount of artifact and the sharpness of anatomic structures such as the right and left hepatic ducts, the extrahepatic bile duct, and the main pancreatic duct), and the reviewers' preference of images. The images were evaluated independently by two radiologists who were unaware of the results of the other cholangiopancreatographic sequence and of the diagnosis.

RESULTS

Artifacts were less prominent in images that were obtained using the single-shot RARE sequence (p = .0192); however, the sharpness of anatomic structures was the same using either sequence (p = .1673). For images that were obtained using the single-shot RARE technique, the sensitivity, specificity, and accuracy in distinguishing malignant from other abnormalities were 83%, 78%, and 80%, respectively; for the multislice HASTE technique, these values were 77%, 72%, and 74%, respectively (p > .05). Disease-specific accuracy in determining the correct diagnosis was 54% and 59%, respectively (p > .05). In patients in whom all the ducts needed to be defined, the single-shot RARE technique was preferred to the multislice HASTE technique (p < .01).

CONCLUSION

The single-shot RARE technique shows fewer artifacts and is preferred to the multislice HASTE technique. However, both techniques show the same degree of sharpness of anatomic structures, both are able to reveal malignant diseases, and both provide enough information to determine a specific diagnosis.

Intraductal mucin-producing tumor of the pancreas: diagnosis by MR cholangiopancreatography

PURPOSE

Our goal was to evaluate the usefulness of MR cholangiopancreatography (MRCP) for intraductal mucin-producing tumor of the pancreas (MPT).

METHOD

Eleven patients with intraductal MPTs (six main duct type; five branch duct type) underwent MRCP. The findings of MRCP were compared with those of endoscopic retrograde cholangiopancreatography (ERCP).

RESULTS

In all of the cases, MRCP could disclose all dilated pancreatic ducts and cysts, some of which were not demonstrated by ERCP. MRCP did not show a signal void of mucin in any of the cases. In the two cases of the main duct type, ERCP showed filling defects of excrescent nodules, which were not seen by MRCP. In the two cases of the main duct type, nodules were seen more clearly by ERCP than by MRCP.

CONCLUSION

MRCP and ERCP are complementary imaging modalities for intraductal MPT.

Magnetic resonance cholangiopancreatography: non-invasive imaging for the biliary tree and pancreatic duct

Producing images similar to those acquired by the invasive procedures of endoscopic retrograde cholangiopancreatography (ERCP) or percutaneous transhepatic cholangiography, magnetic resonance cholangiopancreatography (MRCP) is indicated in patients who are unable to undergo ERCP or have had previously unsuccessful ERCP. It is used increasingly in non-invasive evaluation of the pancreaticobiliary tree in cases where the need for intervention during ERCP is expected to be low. MRCP may help in identifying anomalous biliary anatomy or choledocholithiasis before laparoscopic cholecystectomy, and in deciding between percutaneous or endoscopic treatment for patients with obstructive jaundice to decrease the rate of failed ERCP procedures.