[Characteristics and detectability of RARE technique].

RARE is a kind of fast spin echo technique with large number of echo train and long TE. Because of long TE, signal from parenchyma is vanished and only liquid with long T2, such as bile, pancreatic juice, is detected. Compared to HASTE, signal from vessels like portal or hepatic vein is vanished either. Acquisition time of RARE is extremely short because it is single shot technique. So, on MRCP examination, RARE is good method for easily understanding of whole structure of biliary system because it is usually used as a projection image with thick slice. On the other hand, one should pay attention for shorter T2 bile and pancreatic juice. If their T2 is short, biliary system may not be shown with RARE.