New duct caliber measurement methods on magnetic resonance cholangiopancreatography

PURPOSE: To report the feasibility of new duct caliber measurement methods using signal intensity on MR cholangiopancreatography (MRCP). MATERIALS AND METHODS: A phantom with 0.25-8 mm caliber ducts was imaged with a 1.5-Tesla MR system using the usual MRCP sequence. Each caliber was measured by conventional method (full width at half maximum, FWHM) and two new methods: the maximum intensity measurement method (MIM), in which caliber was calculated from maximum signal intensity, and the area intensity measurement method (AIM), in which caliber was calculated from the area under the signal intensity curve. Errors in calculated caliber were compared among the three methods of measurement. RESULTS: Mean measurement errors of each caliber for 1-8 mm ducts by MIM [14% (2.1-25%)] and by AIM [6.8% (0.4-16%)] were significantly lower than those by FWHM [30% (17-64%)]. AIM was significantly more accurate than MIM for caliber measurement of ducts over 1 mm. CONCLUSION: Two new caliber measurement methods for pancreatobiliary ducts in MRCP, MIM and AIM are accurate and should play an important role in clinical MRCP.