Effects of Intraluminal Irradiation with Holmium-166 for TIPS Stenosis Hayer, Seoul, Korea) and sedation was maintained by an intravenous administration of ketamine hydrochloride (0.01 cc/mL, 1 gtt/sec) during the procedure. The pigs were placed in the supine position for flouoroscopy (Integris 2000, Philips, the Netherlands) with their necks were rotated to the left. After making a skin incision (1 2 cm) under sterile conditions, right external jugular venous access was achieved by using an 18-gauge micropuncture introducer (Green I.V. catheter , Greencross Medical Co., Seoul, Korea), a 0.035-inch Terumo guide wire (Terumo Corporation, Tokyo, Japan) and a coaxial catheter-needle set (RUPS 100, Cook, Charenton, France). A 10-Fr sheath without an inner needle (Cook) was passed to the inferior vena cava and advanced caudally into the right (or middle) hepatic vein. After catheterization of the right hepatic vein, a hepatic venogram and wedge portogram were performed to guide the puncture of the right portal vein. A 16-gauge Colapinto needle set (Cook) was introduced into the hepatic vein. It was rotated ventrally and the tip was firmly fixed against the vein wall. The needle and a 5-Fr catheter Table 1. Exposure Times at the Surface, 0.5 mm and 1.0 mm Away from the Balloon with Two Different Concentration Activities of 166Ho (1,850 MBq and 3,700 MBq) for the Desired Absorbed Dose (30 Gy) Surface 0.5 mm distance 1.0 mm distance Exposure Times with Concentration Activities 1,850 MBq 4.5 min 06.75 min 16.22 min 3,700 MBq 2.25 min 3.38 min 8.1 min0 were passed into the parenchyma toward the anticipated region of the portal vein. After puncture of the right portal vein, this was confirmed by aspiration of venous blood and by injecting a small amount of contrast agent; the needle was removed, and negative pressure was applied to the 5- Fr catheter during slow withdrawal. Once the portal vein was punctured, a 0.035-inch Terumo guide wire and a 5-Fr angiographic catheter were advanced into the main portal vein, and the pressure gradient between the portal vein and the vena cava was measured using a Pharmaseal central venous pressure monitor (Baxter Healthcare Corporation, Valencia, CA). Portal venography was also obtained with injecting contrast media by hand, and this demonstrated the portal venous anatomy and its diameter. Portal hypertension was artificially induced by intrapor- tal injection of 0.02 mL of N-butyl-2-cyanoacrylate (NBCA, sclerosing embolic agent, B-Brawn, Cook) mixed with lipiodol (Lipiodol ultra-fluid, Guerbet, France) (1:3). Under fluoroscopy, this mixture was injected until stasis of the portal flow was achieved, and the portal pressure was measured to confirm the occlusion. The injection volume of the embolic mixture was approximately 1.5 2 mL. After removal of all the needle parts except the superstiff Amplatz-type guide wire and outer sheath, an angioplasty balloon catheter (10 mm in diameter, 4 cm in length) was used to dilate the hepatic parenchymal tract. Balloon dilatation was performed at 3 atm for 4.5 minutes prior to stent insertion. The balloon was filled with a solution of 166Ho in the irradiation group and with a mixture of contrast media (VisipaqueTM 270, Amersham health, Cork, Ireland) and saline (1:1) in the control group, respectively. A B Fig. 1. Follow-up studies done two weeks after TIPS with 166Ho irradiation. A. Portography demonstrates good patency of the shunt without narrowing or occlusion. B. Microscopic examination (Masson-trichrome stain, 10) of the specimen obtained from the parenchymal tract of the patent stent reveals that the luminal surface is lined by a relatively thin, uniform layer of pseudointimal hyperplasia. Pseudointimal hyperplasia (H) is well delineated from the normal liver parenchymal layer (nl). Korean J Radiol 8(2), April 2007 129