Percutaneous Radiofrequency Ablation of Small (1–2 cm) Hepatocellular Carcinomas Inconspicuous on B-Mode Ultrasonographic Imaging: Usefulness of Combined Fusion Imaging with MRI and Contrast-Enhanced Ultrasonography

Table 1

Scoring criteria for evaluation of tumor conspicuity.

Score	Criteria
1	The echogenicity of the index tumor is definitely different from that of the surrounding liver and more than 90% of the tumor has a well-defined margin
2	The echogenicity of the index tumor is slightly different from that of the surrounding liver and more than 50% of the tumor has a well-defined margin
3	The index tumor is nearly isoechoic to the surrounding liver and less than 50% of the tumor has a well-defined margin
4	Definitely unidentifiable

This scoring system was described in our previous study [11] and was established after reviewing previous relevant studies regarding planning US for RFA and making necessary updates [17–19].