AJR:194, February 2010 523 Although several studies have assessed treatment outcomes in patients with liver ma- lignancies, most described imaging features from one or two local therapeutic methods or evaluated posttherapeutic image findings us- ing CT only [9–12]. To our knowledge, this study is the first to describe MR features of ablated lesions after RFA, cryoablation, and microwave ablation performed during 10 years of practice. The aim of this study was to determine whether MR findings in patients with resolved and unresolved liver lesions ablated using RFA, cryoablation, and microwave ablation differ and, if so, to describe the differences. Materials and Methods Patients This study is a retrospective study of patients seen in the MRI service of one institution from Jan- uary 1, 1998, to January 1, 2008. Patients’ records from body MRI and interventional radiology were Thermoablative Treatments for Malignant Liver Lesions: 10-Year Experience of MRI Appearances of Treatment Response Andrea S. Kierans 1 Mohamed Elazzazi 1 Larissa Braga 2 Polytimi Leonardou 1 David A. Gerber 3 Charles Burke 1 Waqas Qureshi 1 Masayuki Kanematsu 4 Richard C. Semelka 1 Kierans AS, Elazzazi M, Braga L, et al. 1 Department of Radiology, University of North Carolina Hospitals and University of North Carolina at Chapel Hill, Campus Box 7510, 2001 Old Clinic Bldg., Chapel Hill, NC 27599-7510. Address correspondence to R. C. Semelka (richsem@med.unc.edu). 2 Department of Radiology, University of Nebraska Medical Center, Omaha, NE. 3 Department of Surgery, University of North Carolina Hospitals and University of North Carolina at Chapel Hill, Chapel Hill, NC. 4 Department of Radiology, Gifu University, Gifu, Japan. Vascular฀and฀Interventional฀Radiology฀•฀Original฀Research AJR 2010; 194:523–529 0361–803X/10/1942–523 © American Roentgen Ray Society L iver malignancies are a common cause of cancer death. Approxi- mately 17,000 people die of liver malignancies each year in the United States [1]. Although surgery is consid- ered the treatment of choice, it is contraindicat- ed in most patients [2, 3]. Minimally invasive ablative therapies have emerged as alternative treatment options for patients not eligible for surgery and for those awaiting liver transplan- tation. Among these techniques, radiofrequen- cy ablation (RFA), cryotherapy, microwave ab- lation, and laser ablation modalities have been the most commonly performed procedures. CT and MRI have been used to depict he- patic lesions, to guide the intervention pro- cess, and to evaluate the response of malig- nant liver lesions after minimally invasive local therapies [4–8]. MRI has been de- scribed as superior to CT in detecting and following up ablated lesions because of its known higher sensitivity and specificity [4]. Keywords: cryoablation, liver lesions, liver malignancies, microwave ablation, MRI, radiofrequency ablation, thermoablation DOI:10.2214/AJR.09.2621 Received February 20, 2009; accepted after revision July 20, 2009. OBJECTIVE. The objective of our study was to describe our 10-year experience using MRI to evaluate response to local thermoablative interventions in the treatment of malignant liver lesions. MATERIALS฀AND฀METHODS. This retrospective study was conducted from 1998 to 2008. MRI studies were performed at 1.5 and 3 T and were acquired < 4, 4–9, and > 9 months after radiofrequency ablation (RFA), cryoablation, and microwave ablation. MR fea- tures were evaluated on the basis of signal intensity on unenhanced T1-weighted images and the presence of ill-defined perilesional enhancement, well-defined lesional enhancement, or washout on contrast-enhanced images. Imaging features were evaluated with all intervention- al modalities together and separately. RESULTS. The study population was composed of 135 men and 36 women (203 ablated lesions) with a mean age of 65 years (range, 39–78 years). When the data for all treatment methods were combined, well-defined lesional enhancement and washout were significant findings among the resolved and unresolved outcome groups regardless of follow-up time cat- egory. After RFA, ablated areas had a tendency to show high signal intensity on T1 images, whereas low signal was seen after cryoablation and a hyperintense rim was seen after micro- wave ablation. Washout was only depicted 9 months after cryoablation but was seen in 12% of lesions < 4 months after RFA. No difference was appreciated on ill-defined perilesional enhancement with all methods combined or separately. CONCLUSION. MRI findings after ablation are dependent on the treatment modality and the length of time between the procedure and follow-up examination. Kierans et al. MRI of Liver Lesions Treated With Thermoablation Vascular and Interventional Radiology Original Research Downloaded from www.ajronline.org by 52.73.204.196 on 05/16/22 from IP address 52.73.204.196. Copyright ARRS. For personal use only; all rights reserved