Planning US for percutaneous radiofrequency ablation of small hepatocellular carcinomas (1-3 cm): value of fusion imaging with conventional US and CT/MR images.

Purpose: To assess whether fusion of conventional ultrasonography (US) with liver computed tomography/magnetic resonance images for planning US for percutaneous radiofrequency (RF) ablation can reduce false-positive detection and enhance lesion detectability of small hepatocellular carcinomas (HCCs) on conventional US.

Materials And Methods: This retrospective study was approved by the institutional review board, and informed consent was waived. A total of 137 patients with single HCCs (mean ± standard deviation, 1.7 ± 0.6 cm; range, 1.1-3.0 cm) were included. Planning US was performed by two radiologists by using conventional US first and fusion imaging later in the same session. The false-positive detection rate of conventional US was assessed with the results of fusion imaging used as a reference standard. True-positive detection rates on conventional US and fusion imaging were compared by McNemar test. Initially undetectable HCCs on conventional US that became detectable after image fusion were also assessed.

Results: The false-positive detection rate of conventional US was 7.7% (nine of 117). Overall true-positive detection rates on conventional US and fusion imaging were 78.8% (108 of 137) and 90.5% (124 of 137), respectively (P = .0002); the rates were significantly different between conventional US and fusion imaging for HCCs smaller than 2.0 cm, but not for HCCs 2.0 cm or larger. Of 20 initially undetectable HCCs on conventional US, nine (45.0%) became detectable after image fusion.

Conclusions: Fusion imaging for planning US for percutaneous RF ablation can reduce false-positive detection and enhance lesion detectability of small HCCs on conventional US.