MR cholangiopancreatography at 3.0 T: intraindividual comparative study with MR cholangiopancreatography at 1.5 T for clinical patients.

OBJECTIVES

To prospectively evaluate the image quality and diagnostic accuracy of magnetic resonance cholangiopancreatography (MRCP) at 3.0 T compared with that at 1.5 T used for patients.

MATERIALS AND

METHODS

This study was approved by our institutional review board, and informed consent was obtained from all patients. Three-dimensional MRCP with both a 1.5-T system and a 3.0-T system was administered to 33 consecutive patients suspected of having biliary and/or pancreatic diseases. For 3-dimensional MRCP imaging, a respiratory-triggered Fast Recovery Fast Spin Echo sequence with the parallel imaging technique was used for both systems. The spatial resolution at 1.5 T was matched to that at 3.0 T, and matrix size was 512 x 160, field of view (FOV) 36 x 36 cm, slice thickness 2 mm, and the number of slices ranged from 44 to 54. Repetition time varied according to the patients' respiratory cycles, which ranged from 3000 milliseconds to 6000 milliseconds, and effective echo time, ranging from 391 milliseconds to 482 milliseconds, was automatically determined by the systems. Contrast of imaging of the common bile duct versus that of the periductal tissue was quantitatively evaluated. The image quality for homogeneity of signal intensity, image noise, susceptibility artifacts, and overall imaging quality and diagnostic accuracy for stenoses of bile and main pancreatic ducts and for pancreatic cystic lesions were qualitatively evaluated. The results for 1.5- and 3.0-T were then compared statistically, by using the paired t test for quantitative evaluation of contrast between the common bile duct and the periductal tissue, the Wilcoxon signed rank test for visual evaluation of the image quality, and the McNemar chi2 test for evaluation of sensitivity and specificity for diagnostic purposes. A P value of less than 0.05 was considered to indicate a statistically significant difference.

RESULTS

Contrast of the common bile duct versus that of the periductal tissue at 3.0 T was superior to that at 1.5 T (P < 0.001). In the visual evaluation, image quality at 3.0 T was superior to that at 1.5 T for evaluation of image noise (P < 0.001), overall image quality (P < 0.001), and delineation of intrahepatic bile ducts (P < 0.01) and the main pancreatic duct (P < 0.05), whereas there were no significant differences in homogeneity of signal intensity and in susceptibility artifacts. The diagnostic accuracy for 3.0 T was approximately equivalent to that for 1.5 T.

CONCLUSION

Our results for patients with biliary and pancreatic diseases demonstrate a marked improvement in contrast of the common bile duct versus that of the periductal tissue and image quality including image noise at 3.0 T compared by 1.5 T when identical spatial resolution configuration were used. The results suggest that 3.0 T may allow higher spatial resolution and offer promise for improved diagnosis in MRCP, although further investigations using optimize scan parameters will be needed before its full potential can be achieved.