PET/CT-guided Tumor Ablations: A Step-by-step Approach

Learning Objectives: To provide an overview of the workflow and key steps in performing a PET/CT-guided tumor ablation procedure. Technical considerations, imaging protocols, pitfalls and mitigation strategies are reviewed through case presentations.

Background: PET/CT-guided tumor ablations are a powerful tool in the interventional oncology armamentarium, enabling precise targeting of tumors and real-time assessment of treatment efficacy. This modality is particularly valuable for treatment of hypermetabolic tumors that may be occult on anatomic imaging and for intraprocedural detection of residual hypermetabolic tumor, allowing immediate retreatment within the same session.

Clinical Findings/Procedure Details: The steps of performing a PET/CT-guided ablation are detailed, using the split-dose protocol. A standard FDG dose (12 mCi) is divided in two parts. The initial tumor targeting dose (one-third of the total dose or 4 mCi) is administered to the patient and a PET/CT is performed after at least 30 minutes to localize the tumor. The initial PET can be fused with subsequent CT scans after needle placement to confirm precise targeting of the hypermetabolic tumor. When misregistration is a concern, a breath-hold PET (short PET acquisition while respiration has been suspended) can be acquired. Following ablation, a treatment efficacy dose (two-thirds of the total dose or 8 mCi) is administered to evaluate ablation completeness. For liver ablations, the pre-ablation PET can be fused with the post-ablation portal venous phase CT, to provide detailed assessment of the ablation margins. Intraprocedural PET metrics are a predictive biomarker of local tumor progression.

Conclusion and/or Teaching Points: PET/CT-guided tumor ablations have several advantages over standard image-guided ablations. Understanding the procedural steps, logistics and pitfalls of this technique are important for wider adoption of these interventions.