Evaluation of intraportal blood flow distribution by four dimensional MR blood flow mapping using subsecond MR imaging

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TrueFISP MR imaging using a selective inversion recovery tagging pulse was performed to evaluate the intraportal venous flow distribution from the superior mesenteric vein and the splenic vein. Tagged blood flow into the portal vein was shown as areas of decreased signal intensity in the portal vein. TrueFISP MR images obtained perpendicular to the portal vein allowed three-dimensional observation of intraportal venous flow distribution. In the study of normal subjects, the blood flow from the superior mesenteric vein and the splenic vein formed streamelined flow in the half of the subjects, but it showed whirled flow in the portal vein in the remaining subjects on the trueFISP MR images obtained perpendicular to the portal vein. TrueFISP MR imaging perpendicular to the portal vein achieved high spatial and high contrast resolution imaging and allowed detailed evaluation of the intraportal venous flow distribution. In our analysis, dark inflow signal to the portal vein from the SMV was … More observed in the right side of the portal vein in 71% at the lower portion while it was seen in the central area of the portal vein in 29% and in the right side in 36% at the upper portion on the oblique MR images perpendicular to the portal vein. Dark inflow signal from the SpV was observed in the left side of the portal vein in 79% at the lower portion while it was seen in the central area of the portal vein in 71% at the upper portion. Whirling flow in the portal vein was observed in 57% on the oblique MR images perpendicular to the portal vein while it was not seen on the coronal MR images. Additionally, four-dimensional blood flow mapping can be performed by serial data acquisition using sebsecond ultrafast MR imaging. In patients with cirrhosis or chronic hepatitis, the whirled flow in the portal vein was often observed probably due to the increased splenic venous flow. The whirled flow may also be associated with the anatomical variations of confluent patterns between the splenic vein and the superior mesenteric vein. In evaluating the influence of fasting and food intake for the portal flow dynamics, we revealed that the portal vein was predominantly perfused by the splenic venous flow before meal while it was predominantly perfused by the superior mesenteric venous flow after meal. Additionally, the superior mesenteric venous flow dramatically increased after meal compared with the fasting state while the splenic venous flow decreased in 41%, increased in 31% and showed no change in 28% of the subjects. Less