The development and the widespread clinical application of various di agnostic imaging modalities, such as diagnostic ultrasonography, X-ray computed tomography, single photon emission computed tomography, and magnetic resonance imaging, have been beyond all expectation. In particular, ultrasonography and X-ray computed tomography have be come major diagnostic tools for diseases of the liver, the biliary tract, and the pancreas. They often have virtually replaced other conventional imag ing modalities including invasive angiography and percutaneous trans he patic cholangiography. One modality...