Magnetic resonance imaging (MRI) has been widely used for small liver lesion detection and characterization. In patients who undergo RFA, MRI is often performed before RFA, whereas immediate technical success is usually assessed by CT. Conventional visual assessment of two modalities may be more challenging than being anticipated, because acquisition position, respiration, and spatial resolution differ between the two. Therefore, the study purpose is to evaluate the results of software-assisted ablative margin assessment using registration of different pre-and post-RFA modalities compared with the conventional method of side-by-side MRI-CT comparison in patients with HCCs.

Inclusion Criteria:

• patients (≥ 18 years) who were referred to our radiology department for liver tumor RFA
• patients who had liver MR images of sufficient quality for pre-RFA evaluation within 30 days before RFA
• patients with 1-3 tumors (<5 cm)

Exclusion Criteria:

• Child-Pugh class C
• any uncorrected coagulopathy
• hypersensitivity to iodine or other reasons that prevented the performance of post-RFA contrast-enhanced CT

Patients with liver tumor and referred to Radiology for RFA.