Effects of Intraluminal Irradiation with Holmium-166 for TIPS Stenosis hemorrhage, tolerated the procedures well during the follow-up period. The TIPS patency of the eleven cases was evaluated using follow-up portal venography and histological analysis two weeks after the procedures. The animals were then tranquilized by an intramuscular injection of 2 mL ketamine hydrochloride and 2 mL xylazine hydrochloride without continuous intravenous injection. Portal venography was obtained by introducting a 5-Fr catheter into the portal vein via the jugular approach. In two cases, in which the craniocaudal passage of the catheter was disturbed by occlusion of the parenchy- mal tract and the caudal part (portal vein portion) could not be visualized, portal venography was performed via the superior mesenteric vein that was exposed after an abdominal wall incision (Fig. 3A). The extent and degree of stent narrowing were assessed by comparing the diameters of the stents immediately after and two weeks after TIPS creation. Shunt occlusion was defined as the absence of flow through the shunt, while shunt stenosis was defined as narrowing of at least 50% of the stent diameter. The animals were then euthanized by an intravenous injection of pentobarbital sodium. The TIPS shunt with a 2 cm rim of surrounding parenchymal tissue was cored out and fixed in formalin solution for two weeks. Thereafter, the stent were sectioned longitudinally at 5 mm thickness intervals. The stent wires were carefully removed with use of a dissecting microscope to minimize damage to the underlying tissue. The cut specimens were processed in paraffin and then transverse sections were obtained perpendicular to the long axis of stent at each level of the portal vein, the parenchymal tract and the hepatic vein. Hematoxylin-eosin (H E) and Masson-trichrome staining methods were used. On the histological examinations, the granulation tissue from the stent to the luminal surface was defined as the pseudointimal hyperplasia and its maximum thickness was calculated for each animal as a percentage of the estimated stent diameter. The histologic characteriza- tion of the pseudointimal hyperplasia was also evaluated. Statistical Analysis For comparing the maximal PIH between the two groups, the statistical analysis was performed with using SPSS version 10.0 and two-sample t-tests; statistical signifi- cance was set at p values < 0.01. Additionally, the mean portal pressures measured in each pig before and after NBCA embolization and also after TIPS stent insertion were compared in order to confirm the successful creation of portal hypertension and TIPS placement. RESULTS Transjugular intrahepatic portosystemic shunt were successfully deployed in all pigs, except in one case of postprocedural death in the control group a day after TIPS creation. The cause of death was intraperitoneal bleeding, and this pig was excluded from the follow-up study. A B Fig. 3. Follow-up studies done two weeks after TIPS without 166Ho irradiation in the control group. A. Portography via the superior mesenteric vein, which was exposed by a skin incision, shows partial occlusion of the shunt at the level of parenchymal tract of TIPS. B. Microscopic cross section revealed a homogeneous layer of granulation tissue that’s composed of an abundant acellular matrix, myofibroblasts and numerous inflammatory cells (between arrows) adjacent the stent wire (w). Korean J Radiol 8(2), April 2007 131