Objective: Evaluate the efficacy of positron emission tomography with 18F-fluorodeoxyglucose (18F FDG PET) in detecting complete ablation both immediately and at 4–6 weeks post-procedure. Examined the impact of post-procedural inflammatory changes on PET-based identification of residual viable tumor. A comparative analysis of 18F-FDG PET and triphasic CT to determine the presence of residual tumor at 4–6 weeks.

Methods: A prospective study of forty-three patients with hepatic focal lesions who performed 18F-FDG PET/CT at three-time zone; before the intervention, same day post RFA, and 4-6 weeks post ablation. Triphasic CT was performed before the intervention and 4-6 weeks after ablation. Standard diagnostic indices including sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and diagnostic efficacy were calculated. Diagnostic performance of FDG PET/CT and triphasic CT 4-6 weeks after ablation were compared.

Results: PET/CT determined complete ablation immediately and 4-6 weeks post-intervention in 37 (86%) patients. PET/CT detected incomplete ablation in 4 (9.5%) patients immediately and in 5 (11.5%) patients 4-6 weeks post-ablation. PET/CT sensitivity, specificity, PPV, NPV, and accuracy were 66.7%, 100%, 100%, 94.9%, and 95.3%, respectively on the same day and were 80%, 100%, 100%, 97%, and 97.5%, respectively 4-6 weeks post ablation. The rim-shaped FDG uptake linked to post-ablation inflammatory changes did not appear to interfere with image interpretation, either immediately or 4–6 weeks post-procedure. No statistical difference in diagnostic performance between the two imaging modalities 4-6 weeks post ablation (chi-square value of 2.0, P value=0.157).

Conclusion:18F FDG PET can serve as an immediate and early indicator for incomplete ablation.