1. Taylor J Greenwood, MD, Adam Wallace, MD, Aseem Sharma, MD, Jack Jennings, MD, PhD

2. L1 pathologic compression fracture from metastatic breast cancer treated with radiofrequency ablation (RFA)  Non-enhancing ablation zone  Signal void is from vertebral augmentation cement (*).  At 1 week:  Diffuse edema  Hyperemia  At 3 months :  Rim of granulation tissue and hemorrhagic congestion STIR T1 FS C+ * * BeforeAfter 1 week3 months

3. L3 metastatic renal cell carcinoma treated with stereotactic radiation followed 10 months later by RFA  Tumor recurrance peripherally  At 2 months after RFA :  Paraspinal muscle inflammation  Mild residual hyperemia  Granulation tissue, stable for >1 year T2 T1 FS C+ T2 T1 FS C+ Before 2 months After

4. In contrast to the previous example... L1 small cell lung cancer metastasis treated with RFA  Zone of ablation  Residual tumor  Salvage Radiation Therapy resulted in tumor retraction * * T1 FS C+ T2 T1 FS C+ Pre-Tx 2 months

5. S4 rectal cancer metastasis treated with cryoablation  CT guidance shows the “ice ball” delineating the ablation zone.  At 4 months: MRI and PET/CT correlation  Coagulation necrosis  Hemorrhagic congestion is seen just like RFA  PET/CT shows no uptake in the ablation zone, but disease progression was seen at contiguous levels Cryoablation Sag T2 Axial T1 FS Pre-C PET/CT * *

6. Post contrast images show tumor enhancement at S3 and necrosis from ablation at S4 DWI can be helpful adjunct tool in evaluating post treatment changes from tumor.  Tumor often has diffusion restriction  Coagulation necrosis has rapid diffusion (relatively lower high b value signal and increased ADC) DWI ADC S3 No Tx S4 s/p cryoablation T2T1 FS C+

7. Sacral rectal cancer metastasis 1 month after RFA.  T2 heterogeneous, T1 hyperintensity within the ablation zone: hemorrhage or tumor? T1 FS C+ T2 FST1 CTSubtraction Subtraction images are helpful in differentiating residual tumor from hemorrhage.

8. L5 = RFA treated lesion with marrow fibrosis L4 = viable metastatic disease Tumor Fibrosis T1 T2T1 FS C+ PET/CT PET/CT can detect residual hypermetabolic disease before symptoms return and helps differentiate tumor from granulation tissue

9. 1 month 11 months 3 months 8 months L4 leiomyosarcoma metastasis treated with RFA.  Patient developed recurrent back pain.  PET/CT was performed just prior to biopsy.  Final Pathology: Marrow Fibrosis When clinical and imaging parameters are discordant, percutaneous biopsy should be considered before re-treatement.

10.  Post Ablation changes evolve over the first several months due to an inflammatory response  Margin of Enhancement:  Thin, smooth = expected treatment change  Thick or increasing enhancement does not always equal tumor  When clinical and imaging parameters are discordant, biopsy should be considered before re-treatment.  PET/CT and DWI are useful in evaluation of residual or recurrent tumor.