Manual versus automatic image fusion of real-time ultrasonography and MR/CT images for radiofrequency ablation of hepatic tumors: A preliminary report of a randomized prospective trial

Purpose: To compare the registration error, time required for image fusion and technical success rate of manual and automatic image fusion of ultrasonography (US) and MR/CT images for radiofrequency ablation (RFA) of hepatic tumors.

Materials and methods: 26 consecutive patients with hepatocellular carcinomas (HCC) or colorectal liver metastases (CRLM) were prospectively enrolled in this study. Patients are randomly assigned to a) manual image fusion group, or b) automatic image fusion group. Two interventional radiologists performed RFA for hepatic tumors with manual or automatic image fusion of real-time US and MR/CT. Time for image registration (s), number of point locks, registration error (cm) and technical success rate were compared between manual group and automatic group. Mann Whitney U-test and Fisher's exact test was performed for statistical analyses and p-values less than 0.05 were considered as statistically significant.

Results: 15 HCCs and one CRLM were treated using manual image fusion and 13 HCCs and one CRLM were treated using automatic image fusion. Mean sizes of hepatic tumors were 1.67 cm for manual fusion and 1.54 cm for automatic fusion (p = 0.623). Averages of time for image registration, number of point locks and registration error were 156 s, 3.1 and 0.76 mm for manual group, and 201 s, 3.0 and 0.80 mm for automatic group, respectively, and there were no significant difference (p-value = 0.5582, 0.8218 and 0.8058). Technical success rate was 100% (16/16) for manual group and 92.9% (13/14) for automatic group and there was no significant difference between each other. (p = 0.4667).

Conclusion: Technical performance of manual and automatic image fusion is comparable for RFA of hepatic tumors.