Contrast-enhanced Ultrasound (CEUS) Follow-up After Radiofrequency Ablation or Cryoablation of Focal Liver Lesions: Treated-area Patterns and Their Changes over Time

Objectives: To describe the early patterns of liver lesions successfully treated with radiofrequency ablation (RFA) or cryoablation (CA) and their changes over time.

Methods: Twenty-two RFA-treated and 17 CA-treated patients underwent CEUS from week 1 to year 3 post-ablation. Patterns, margins and volumes of RF-induced and cryolesions were evaluated and compared over time.

Results: After contrast enhancement, shortly after ablation, undefined margins with persistent enhancing small vessels penetrating >2 mm into the treated zone were significantly more frequent after CA (67 %) than RFA (22 %) (P < 0.02). During the arterial phase, a thin, enhancing marginal rim was seen during week 1 (T1) in around 28 % of RF lesions, while 75 % of cryolesions had thick enhancing rims (P < 0.02). The mean RF-induced lesion volume, maximum at T1 (44.1 ± 37.5 ml), shrank slowly over time, remaining clearly visible at 1 year (8.3 ± 7.4 ml). Cryolesions shrank faster (P = 0.009), from an average of 16.6 ± 7.1 ml at T1 to 1.7 ± 1.3 ml 1-year post-ablation.

Conclusion: RF-induced and cryolesions differ, particularly their margins and shrinkage rates. Knowing these differences allows avoidance of incomplete treatment or falsely diagnosed recurrence, especially after CA.

Key Points: • Contrast-enhanced ultrasound (CEUS) provides new follow-up information following hepatic radiological inyervention. • CEUS provides good visualisation of vascular modifications after thermoablation. • RFA-induced lesions and cryoablated lesions differ. • Knowledge about RF and cryolesion patterns is essential for correct CEUS follow-up. • Cryolesions have thicker peripheral inflammatory reactions and shrink faster than RFA-induced lesions.