Radiofrequency Ablation of Liver Lesions

Although there is considerable variation in the recommended timing of PET/CT imaging after radiofrequency ablation of liver lesions, PET/CT has shown considerable utility for detecting recurrent/residual disease.

Some advocate post-procedure PET/CT imaging 24-48 hours after ablation to assure that the entire lesion has been fully treated (any remaining FDG uptake at this very early stage should represent residual active tumor, not post-procedural inflammation).

Later follow-up can then often performed, as clinically warranted (often at 3 and 6-months).

Benign Findings:  

• Complete absence of metabolic activity in an ablated lesion is consistent with successful treatment. 
• A homogeneous rim of well-defined peripheral hypermetabolic activity surrounding a non-avid hypodensity is presumed to represent post-ablation inflammatory changes. 

The peripheral nature of this uptake is often best appreciated on the coronal images. 

Recurrent/Residual Malignancy: 

• Any nodular or focal uptake within or abutting the ablated lesion is highly suspicious for malignancy.