RF Ablation: indication, technique and imaging follow-up Trongtum Tongdee, M.D. Radiology Department, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok, Thailand
Objective Basic knowledge of thermal ablation Indications Technique Imaging during and after ablation
Treatment for lung cancer Surgery Thoracotomy, Mini-thoracotomy, Minimal Invasive (VATS/Robotic) Lobar (pneumonectomy, lobectomy) Sub-lobar Resection Chemotherapy Target Therapy Radiation Stereotactic radiotherapy
Ablation is not limited to Radiofrequency Thermal ablation Radiofreqeuncy Microwave HIFU Cryoablation Non thermal Irreversible electro poration (IRE)
Thermal Ablation Basic Concepts Apply heat to specific area with intention of tissue destruction Thermal injury to cell begin at 45 C 8 minutes at 46 C to kill malignant cell 2 minutes at 51 C Protein denature at 60 C Typical RFA > 100 C
How to generate heat?
High frequency alternating electrical current heating tissue surrounding electrode
How to send heat to specific area? Electromagnetic energy 375-500 khz Variety of available electrode Monopolar or bipolar system
Thermal Ablation : Best Practice Destroy tumor : Heat tissue 50-100 C for more than 8 minutes 5-10 mm ablation margin to cover microscopic tumor extension Not disrupt overall functional reserve
Indication Primary Lung Cancer NSCLC stage IA and IB size < 3 cm curative > 5 cm : non curative Metastatic < 4 cm, number < 5 Colorectal Hepatocellular carcinoma Chest wall Bone metastasis (pain relief)
Contraindications Uncontrolled Coagulopathy Predominant endobronchial lesion Relative Tumor near large bronchus, blood vessel or heart FEV1 < 0.8 Cardiac Pacemaker
Ideal Lesion Small tumor : < 3 cm Peripheral : > 2 cm from mediastinum Surround by lung parenchyma
Pre Procedure CT : Size, Number, location, proximity of vital structure PET : assess for nodal or extra-thoracic disease
During Procedure Image Guidance Ultrasound CT, CT fluoroscopy Moderate sedation RFA electrode place into center of tumor
Ablation zone : CT Findings Ground Glass Opacity (Safety Margin) Edema Hemorrhage Cavitation Lack of enhancement < 15 HU
Imaging Follow up CT with contrast 1-2 months Rim enhancement is normal May increase size within 3 months FDG-PET-CT 3-6 months
Complete Response GGO surrounding tumor in all planes is best predictor Lack of enhancement show complete necrosis Cavitation seen in 25% and appears 1-4 months Fluid filled Linear strands or bubble lucencies may appeared
77 yo Male, HCC with sub pleural metastasis
3 months 6 months 3 years 4 years 5 years
56 yo Female, CA colon with lung metastasis
GGO Surrounding nodule
3 months F/U : Lack of central enhancement
3 months 6 months 12 months 24 months
37 yo male, HCC with Lung Metastasis
Cavitation
3 months F/U: Linear Strand
10 months F/U
75 yo Female, Primary lung cancer
2 months F/U : Tumor necrosis
2 nd session : pneumothorax with chest tube
Incomplete Response Enlargement of ablation zone after 6 months Increase enhancement > 15 HU Nodular enhancement FDG advidity Seeding or satellite nodule
38 yo Female, HCC with lung metastasis
2 separation session
1 month F/U
3 months F/U : Nodular Enhancement
55 yo Male, CA Colon with lung metastasis
Pneumothorax
1 year F/U : Enlargement after 6 months
57 yo male, HCC with lung metastasis
1 months F/U
2 months F/U
6 months F/U : Recurrence????
14 months F/U
Complication Pneumothorax Pleural effusion Hemorrhage Subcutaneous emphysema Bronchopleural fistula
60 yo Male, HCC with multiple lung metastasis
Hemorrhage along tract
1 months F/U
76 yo, male checkup
Biopsy
RFA in same session
1 month F/U
45 yo Female, CA thyroid with chest wall mets
Pre 3 months 8 months
52 yo male, right adrenal metastasis
3 months F/U
6 months F/U
Take Home Message Thermal ablation is relative recent minimal invasive modality to treat limited volume lung tumor/chest wall Promising long-term survival and local tumor control Imaging findings different between post ablation and tumor progression
77 yo Male, HCC with lung metastasis
During RFA
1 months 4 months
2 months F/U
6 months F/U
12 months F/U