Original Article Usefulness of the hyperechoic rim for assessing the therapeutic efficacy of radiofrequency ablation in hepatocellular carcinoma patients Takahide Uehara, Masashi Hirooka, Yoshiyasu Kisaka, Masanori Abe, Yoichi Hiasa and Morikazu Onji Department of Gastroenterology and Metabology, Ehime University Graduate School of Medicine Aim: During radiofrequency ablation (RFA) for hepatocellular carcinoma (HCC), a hyperechoic rim develops around the HCC nodules. The usefulness of the hyperechoic rim to guide treat- ment was assessed. Methods: RFA was first performed in pig livers to determine the significance of the hyperechoic rim. Fifty-five patients with 75 HCC nodules had received RFA for the treatment of HCC. For those patients, we evaluated whether conventional ultra- sonography (US) could be used instead of contrast-enhanced computed tomography (CECT) and contrast-enhanced ultra- sonography (CEUS) using virtual imaging. Finally, 31 patients with 45 HCC nodules received RFA, and the degree of ablation was assessed based on the hyperechoic rim. Repeated RFA was done when ablation appeared incomplete. Results: In the pig livers, the hyperechoic rim was found to be related to the presence of dead cells. The preliminary study showed that US could be used instead of CECT and CEUS to evaluate the degree of ablation caused by RFA. Because hepatic vessels in the back side of the hyperechoic rim were not clear by the artifact, we used the distance from the surface of the liver to the hyperechoic rim for evaluation. By analyzing the extent of the hyperechoic rim, it was noted that incomplete ablation was achieved in 17 of 31 patients (21 of 45 HCC nodules). These patients were re-treated with RFA within 5–15 min of the first RFA. Conclusion: This study shows that the hyperechoic rim is related to the presence of dead and necrotic tissues. Thus, assessment of the hyperechoic rim’s characteristics allows one to evaluate the efficacy of RFA. Key words: hepatocellular carcinoma, hyperechoic rim, radiofrequency ablation INTRODUCTION H EPATOCELLULAR CARCINOMA (HCC) is one of the most common malignant tumors world- wide. 1,2 Whenever possible, the HCC nodules are resected surgically. 3,4 Unfortunately, hepatic resection can be performed in only a small percentage of patients due to patients’ lack of hepatic reserve caused by coex- isting cirrhosis or the presence of multiple nodules. Thus, percutaneous ethanol injection (PEI), 5,6 micro- wave coagulation therapy (MCT), 7 and radiofrequency ablation (RFA) 8,9 are used as percutaneous local treatments for unresectable small HCC. Of these approaches, RFA is now widely used to treat HCC nodules, especially small HCC nodules, around the world. 10 Contrast-enhanced computed tomography (CECT) is usually performed 3–4 days after RFA to assess its therapeutic efficacy. 11,12 If residual HCC nodules are detected by CECT, a second round of RFA is performed, usually 4–5 days after the first RFA. Recently, we reported that abdominal contrast- enhanced ultrasonography (CEUS) may be used instead of CECT to assess the efficacy of RFA in HCC patients. 13 In that study, we found that, on conventional ultra- sonography (US), a hyperechoic rim was seen around the necrotic area approximately 5–15 min after RFA. Because this hyperechoic rim resembles the necrotic area depicted by CECT and CEUS, it could likely be used to evaluate whether the RFA had completely destroyed the HCC nodules. This knowledge would help determine the need for further RFA treatment. However, prior Correspondence: Dr Masashi Hirooka, Department of Gastroenterology and Metabology, Ehime University Graduate School of Medicine, Shitsukawa, Toon, Ehime 791-0295, Japan. Emai: masashih@m.ehime-u.ac.jp Received 30 November 2008; revision 1 April 2009; accepted 10 April 2009. Hepatology Research 2009; 39: 954–962 doi: 10.1111/j.1872-034X.2009.00537.x © 2009 The Japan Society of Hepatology 954