Assessment of Treatment Efficacy Immediately After Combined Therapy of Ultrasound-Guided Radiofrequency Ablation and Conventional Transcatheter Arterial Chemoembolization for Hepatocellular Carcinoma: Comparison Between Multidetector-Row CT and MRI

Background: In the case of combined therapy, potential accumulation of iodized oil (lipiodol) in the liver parenchyma around the index tumor may directly interfere with the imaging evaluation of the treatment efficacy immediately after the procedure. We postulated that magnetic resonance imaging (MRI) has the potential to precisely evaluate the ablation zone immediately after radiofrequency ablation (RFA) combined with conventional transcatheter arterial chemoembolization (TACE) for hepatocellular carcinoma (HCC) because the effect of lipiodol retention on MRI signal intensity is minimal. Objectives: To prospectively compare multidetector-row CT (MDCT) and MRI for evaluation of the ablative margin (AM) and index tumor immediately after combined treatment with conventional TACE and ultrasound-guided RFA for HCC. Patients and Methods: This study included 33 consecutive patients with 45 HCCs in whom both contrast-enhanced MDCT and MRI were performed immediately after RFA combined with TACE. Two radiologists independently reviewed the images in terms of the ease of visually discriminating between the AM and index tumor (positive versus negative target sign) and the AM status within the RFA zone. The AM status was divided into AM-plus (completely surrounding tumor), AM-zero (partly discontinuous, without bulging tumor portion), and AM-minus (partly discontinuous, with bulging tumor portion). The McNemar test and kappa statistics were used to compare the CT and MRI data for the incidence of a target sign. The clinical and imaging features were analyzed for the correlation with the local tumor progression using univariate and multivariate analysis. Results: The AM and index tumor were visually discriminated within the ablation zone in 36 (80%) and 40 (88.9%) of 45 ablation zones on MDCT and MRI, respectively (P = 0.387; slight agreement, k = 0.0). On the basis of the results of MDCT and MRI, AM status was classified as AM plus (n = 27 and 31, respectively) and AM zero (n = 9 each). Local tumor progression occurred significantly less in cases with AM-plus on MDCT (P = 0.015) and MRI (P = 0.023) during the follow-up period. Conclusion: MDCT and MRI had equivalent ability to differentiate between the AM and index tumor within the ablation zones immediately after RFA combined with TACE.