Effects of Intraluminal Irradiation with Holmium-166 for TIPS Stenosis: Experimental Study in a Swine Model Ji Seon Park, MD, PhD1 Joo Hyeong Oh, MD, PhD1 Deog Yoon Kim, MD, PhD2 Yong Koo Park, MD, PhD3 Sang Joon Park, MD4 Soo Joong Kim, MD, PhD5 Index terms : Radiations Radiology, Interventional Hypertension, Portal Portasystemic Shunt Transjugular Intrahepatic Korean J Radiol 2007;8:127-135 Received March 14, 2006; accepted after revision April 25, 2006. 1Department of Diagnostic Radiology, Kyung Hee University Medical Center, Seoul 130-702, Korea; 2Department of Nuclear Medicine, Kyung Hee University Medical Center, Seoul 130-702, Korea; 3Department of Pathology, Kyung Hee University Medical Center, Seoul 130- 702, Korea; 4Department of Diagnostic Radiology, Kang Dong Sacred Heart Hospital, Hallym University, Seoul 134- 010, Korea; 5Department of Cardiology, Kyung Hee University Medical Center, Seoul 130-702, Korea Supported by a grant from the Research fund, Ministry of Health and Welfare, Republic of Korea. Address reprint requests to: Joo Hyeong Oh, MD, Department of Diagnostic Radiology, Kyung Hee University Medical Center, 1, Heokidong Dongdaemun-gu, Seoul 130-702, Korea. Tel. (822) 958-8623 Fax. (822) 968-0787 e-mail: ohjh6108@hanmail.net Korean J Radiol 8(2), April 2007 Objective: We wanted to evaluate the effectiveness of intraluminal irradiation with Holmium-166 (166Ho) for reducing the pseudointimal hyperplasia (PIH) in the transjugular intrahepatic portosystemic shunt (TIPS) tract in a swine model. Materials and Methods: TIPS was performed in 12 domestic pigs, after the creation of portal hypertension by intraportal injection of a mixture of N-butyl-2- cyanoacrylate (NBCA) and lipiodol. Five pigs first underwent intraluminal irradia- tion (30 Gy) in the parenchymal tract with using a 166Ho solution-filled balloon catheter, and this was followed by the placement of a nitinol stent in the TIPS tract. For the seven control pigs, the balloon was filled with saline and contrast media mixture. Two weeks later, follow-up portography and histological analysis were performed. Results: TIPS was successfully performed in all twelve pigs with achieving arti- ficially induced portal hypertension. Portography performed two weeks after TIPS showed the patent tracts in the TIPS tracts that were irradiated with 166Ho (5/5, 100%), whereas either completely (5/6, 83.3%) or partially (1/6, 16.7%) occluded TIPS were seen in the seven pigs of the nonirradiated control group, except in one pig that experienced periprocedural death due to bleeding. Histological analysis showed a statistically significant difference for the maximal PIH (irradiat- ed: 32.8%, nonirradiated: 76.0%, p < 0.001) between the two groups. Conclusion: Intraluminal irradiation with 30 Gy of 166Ho for TIPS significantly improved the TIPS patency in a swine model of portal hypertension during a 2- week period of follow-up. T he transjugular intrahepatic portosystemic shunt (TIPS) procedure is widely used for portal decompression in the setting of portal hyperten- sion complicated by variceal hemorrhage or intractable ascites. However, the follow-up data has demonstrated the limited long-term patency of TIPS, and the resultant recurrent portal hypertension and rebleeding have occurred by one year in up to 50 60% of the cases due to stenosis or occlusion of TIPS (1). The previous clinical and experimental studies have reported that the causes of TIPS malfunction were thrombosis during the early stage (within 2 weeks), and pseudointi- mal hyperplasia (PIH) within the stented lumen of the hepatic parenchymal tract and intimal hyperplasia within the outflow hepatic vein during the delayed stage (2 4). Histologically, PIH, which is the main cause of stenosis, is initially made of loose granulation tissue that’s formed by edema, myofibroblasts, neo-capillaries, collagen fibers and inflammatory cells. Thereafter, it is thickened by the increased myofibrob- lasts and collagen fibers. PIH in TIPS has known to be pathogenically similar to myointimal hyperplasia after arterial stenting, and the over-proliferation that occurs in 127