The purpose of this exhibit is to: 1. Describe the methods and timeline for post-RFA follow-up. 2. Recognize characteristic imaging features, and contrast enhancement pattern, and size of the post-RF ablation zone. 3. Identify key imaging features, and enhancement and growth patterns suggestive of partial ablation and/or tumor recurrence.

1. Methods for follow-up: CT w/o contrast, CT w/ contrast nodule densitometry, PET 2. Timeline for follow-up: Post-procedure, 1, 4, 6, 9, 12 mos 3. Early (immediate-1 wk) CT appearance: sectorial hyperemia 4. Intermediate (1-2 mos) CT appearance: bubble lucencies 5. Late (>2 mos) CT appearance: patchy hyperdensity 6. Post-RFA zone contrast enhancement pattern: peri-ablational enhancement 7. Tumor recurrence contrast enhancement pattern: central/nodular enhancement 8. PET

Image-guided RFA has emerged in recent years as a safe and viable treatment option for pulmonary malignancies. Understanding the timing of follow-up and expected post-RFA zone CT appearances is critical for the early identification of tumor recurrence. Characteristic and worrisome imaging features, and contrast enhancement and growth patterns of the post-RFA zone at specific time points in the post-RFA period are detailed. The role of PET as a complement to CT is described.