Is there a need for MRI within 24 hours after CT-guided percutaneous thermoablation of the liver?

Ringe, Kristina Imeen; Wacker, Frank; Raatschen, Hans-Jürgen

BACKGROUND Radiofrequency (RFA) and microwave ablation (MWA) are established minimally invasive techniques for treatment of hepatic tumors. PURPOSE To compare technical success and accuracy of hepatic thermoablation using computed tomography (CT) and magnetic resonance imaging (MRI) acquired 24 h after ablation with regard to evaluation of the post-interventional ablation zone and local tumor recurrence (LTR), and to assess whether additional MRI within 24 h is beneficial. MATERIAL AND METHODS Thirty-two patients (23 men, 9 women; mean age, 60 years) with 48 lesions were included in this retrospective study. CT was performed immediately and MRI was performed 24 h after ablation. Diameter and volume calculations of the ablation zone were compared (T-Test). Technical success and ablation margin distinction, shape, and configuration were evaluated (κ-statistic). Local effectiveness was calculated based on follow-up imaging. Technical success and ablation margin features were correlated with LTR (log-rank test, Fisher's exact test). RESULTS Ablation zone volumes were significantly higher with MRI compared to CT (P < 0.05; mean volume, 55.19 and 45.97 mL). Agreement between CT and MRI for technical success was good (κ = 0.801) and for margin conspicuity fair (κ = 0.289). LTR was 26.1% (mean follow-up, 11.7 months). LTR showed no correlation with technical success or margin conspicuity. CONCLUSION CT and MRI are suited for early evaluation of technical success after thermoablation. Within 24 h a significant increase of the ablation volume is observed, which has to be taken into account when interpreting immediate postprocedural imaging and treating lesions near critical structures. Additional MRI 24 h after ablation seems of limited value regarding prognosis of LTR, especially with regards to evaluation of ablation margin shape and conspicuity.