Evaluation of intraportal venous flow distribution by unenhanced MR angiography using tagging pulse

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Portal flow imaging using unenhanced MR angiography techniques was performed for normal subjects to evaluate the intraportal venous flow distribution from the superior mesenteric vein and the splenic vein. At first, unenhanced MR angiographic images without using tagging pulse were obtained as referenced images of the portal vein. In these images, the portal vein is shown as high signal intensity. Then, tagging pulse was placed on the superior mesenteric vein to suppress the inflow signal from the superior mesenteric vein. As a result, the superior mesenteric venous inflow is demonstrated as areas of decreased signal in the portal vein. The same technique was applied to the splenic vein. In this study, we showed that the superior mesenteric venous flow mainly entered into the right side of the main portal vein forming the streamlined flow while the splenic venous flow mainly entered into the left side of the main portal vein in the normal subjects.As the next analysis, we evaluated the … More influence of fasting and food intake for the portal flow dynamics. In this study, 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.In clinical study, we evaluated the pattern of the intraportal venous flow distribution in cirrhotic patients. In cirrhotic patients, we sometimes observed the superior mesenteric venous flow entering into the left side of the main portal vein and the splenic venous flow entering into the right side of the main portal vein forming the streamlined flow. Additionally, the reversed flow from the superior mesenteric vein into the splenic vein can be observed in cirrhotic patients. These facts indicate that portal venous flow dynamics in cirrhotic patients may be different from that in normal subjects. Less