[Basic evaluation of the optimal flip angle for hepatocyte phase with gadolinium ethoxybenzyl diethylenetriamine pantaacetic acid: selection of the optimal flip angle by the imaging findings].

Gadolinium ethoxybenzyl diethylenetriamine pantaacetic acid (Gd-EOB-DTPA) is incorporated into liver cells, and liver parenchyma show hyperintensity due to the T1 shortening effect. The T1 value of liver parenchyma in the hepatocyte phase changes from the pre-contrast phase. However, in patients with liver dysfunction, the difference of T1 value is generally small. In examination of hepatic disease, the optimal flip angle should be selected according to the patient's state. The definition of hepatic dysfunction based on biochemical data is diverse. Therefore, if the image findings can estimate liver dysfunction, the operator will select the optimal flip angle. Hence, we defined the criteria of liver dysfunction based on the image data; one or more of the following abnormalities-irregular liver surface, splenomegaly, and expansion of portal trunk. In classification by imaging data, we compared the T1 value of liver parenchyma in the hepatocyte phase, and found that the T1 value was significantly different between normal and cirrhotic liver. Then, in a phantom study simulating normal and cirrhotic liver, we set the optimal flip angle (FA)-21 degrees for the normal liver state, and 18 degrees for the LC state. In Gd-EOB-DTPA-enhanced study, the operator can select the optimal FA for each patient according to the image findings.