Magnetic resonance cholangiopancreatography
(MRCP), when performed with heavily T2-weighted fast spin-echo sequences
and a phased-array torso coil, provides high-resolution images of the biliary
tree and pancreatic duct in multiple planes of section. Use of maximum-intensity
projection (MIP) reformations is helpful when overall three-dimensional
views are needed (eg, in cases of cholangiocarcinoma), but the source image
must be carefully compared with the MIP reformation to avoid missing potential
filling defects and other important details obscured by the reformation.
Preliminary work indicates that the accuracy of MRCP is comparable to that
of endoscopic retrograde cholangiopancreatography in diagnosing the cause
of bile duct obstruction. At MRCP, bile duct stones appear as hypointense
foci within high-signal-intensity ducts, and stones as small as 2 mm in
diameter can be seen. In cases of cholangiocarcinoma, the main advantage
of MRCP is that it can noninvasively provide a three-dimensional overview
of the biliary tree, which can help in planning treatment. However, the
limited spatial resolution of MRCP curtails its role in the characterization
of bile duct stenosis, visualization of small intraampullary tumors, and
diagnosis of chronic pancreatitis. MRCP is an important adjunct to traditional
pulse sequences in the work-up of pancreatic and biliary diseases.
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