Postablation assessment using follow-up registration of CT images before and after radiofrequency ablation (RFA): prospective evaluation of midterm therapeutic results of RFA for hepatocellular carcinoma

The purpose of this study was to prospectively evaluate the diagnostic impact of prototypic software that allows registration of CT images before and after radiofrequency ablation (RFA) for safety margin assessment, as well as to determine the therapeutic impact of this software on local tumor progression in comparison with the conventional method of side-by-side CT comparison. One-hundred fifty patients with a single hepatocellular carcinoma (HCC) referred for RFA were enrolled. CT scans were obtained before and after RFA, and all CT images were analyzed with and without the use of nonrigid registration software. Thereafter, local tumor progression in the study group (n = 150) was compared with that in a matched control group (n = 90) in which side-by-side comparison of CT images before and after RFA was used for safety margin assessment. RFA using registration software-assisted diagnoses to decide whether additional RFA was necessary resulted in a 10.67% local tumor progression rate 42 months after the procedure, which was significantly better than that in the matched control group (23.33%) (p = 0.01). After registration software was used, 15.33% (23/150) of patients had conflicting assessments on the safety margin and the necessity for additional RFAs compared with the initial visual comparison of the CT scans. The addition of follow-up registration of CT images before and after RFA resulted in significantly improved assessment of safety margins, simplifying the decision of whether to perform additional treatments and reducing local tumor progression of HCCs after RFA.