Park et al. The irradiation source and its dosage were already described in the previous section. A 9-Fr sheath was advanced into the portal vein follow- ing the slightly deflated balloon catheter. Finally, a nitinol self-expandable stent (10 mm in diameter, 7 cm in length, Niti-S TIPS stent, TaeWoong Medical Co., Koyang, Korea), was placed in the parenchymal tract. The stent position was intended to extend a short distance (about 1 cm) beyond the hepatic vein ostium into the inferior vena cava in the cranial direction and approximately 1 2 cm or more into the portal vein in the caudal direction. The stents were successfully expanded without additional balloon dilatation. Measurements of portal pressure and portogra- phy were performed again immediately after stent deploy- ment. Follow-up Study All 11 animals, except one pig that died of peritoneal A B C D Fig. 2. Follow-up studies done two weeks after TIPS without 166Ho irradiation in the control group. A. Portography via the transjugular approach demonstrates the complete occlusion of the shunt. B. The corresponding gross specimen before removal of the stent wire shows marked ingrowth of fibrotic tissue (arrow) within the parenchymal tract, which is in contrast to the lack of significant narrowing at both venous ends (H, hepatic venous end; P, portal venous end). C. Transverse section (Masson-trichrome stain, 10) through the parenchymal tract of TIPS reveals the complete luminal occlusion with the most superficial layer of fibrin (F), thick granulation tissue and the inflammatory reaction. The removed portions of the wires (arrowheads) are seen as holes. These stent holes are seen adjacent to the normal parenchymal tissue (nl), which is clearly demarcated from the PIH. D. Close-up (Masson-trichrome stain, 100) of the PIH shows numerous spindle-shaped myofibroblasts (arrows) and the abundant collagen matrix. 130 Korean J Radiol 8(2), April 2007