1. Andrew Wright MD, Chris Johnson, Fred Lee Jr. MD, and David Mahvi MD
Comparison of Microwave and Radiofrequency Ablation of Hepatic Tissue in a Porcine in vivo Model.
Andrew Wright MD, Chris Johnson, Fred Lee Jr. MD, and David Mahvi MD
Departments of Radiology and Surgery
University of Wisconsin Hospital

2. Microwave Ablation Theoretical advantages over radiofrequency ablation
No ground pad
Not limited by tissue charring and impedence changes
Larger zone of active heating
Use of Multiple Probes

3. Hypothesis
Because microwave and radiofrequency ablation are both heat based, there will be no difference in ablation size or lesion pathology between the two technologies

4. Methods Microwave Ablation Vivant Medical prototype system
10 minute ablation, 40 Watts
Radiofrequency Ablation
RITA Medical Systems Starburst
10 minute ablation, 3cm deployment 100oC target temperature

5. Microwave Ablation System
3.6cm length of actively radiating antenna
• Vivant Medical
• 13g, 15cm dipole antenna
• 915MHz generator
• Fiberoptic temperature monitor

6. Radiofrequency Ablation System
• RITA Medical
• 14g, 15cm expandable array
• 460 kHz generator
• Integrated thermocouple

7. Treatment Protocol Nineteen crossbred female swine
0, 2, and 28 day survival groups
Mix of MW and RF lesions in each animal
Pathology, serial CT scanning
28 Day survival group
4 MW or 4 RF lesions in each animal
Pathology, serial lab draws

8. Lesion Volume * *
* p=.02

9. Lesion Length * ▪ ▪ ◦ * ◦
* p<.001
▪ p=.02
◦ p<.001

10. Lesion Diameter

11. Laboratory Data
No significant difference in AST, ALT, LDH, Alkaline Phosphatase, WBC, or HCT *
* p<0.001

12. Pathology
48o
RFA MW
Immediate
4 weeks

13. CT Imaging
48 Hours
4 Weeks

14. Summary MW lesions longer than RF
Pathological and radiologic characteristics similar between RF and MW ablation
Both MW and RF cause thrombocytopenia at 48 hours
MW ablation technically easier than multiple-prong RF ablation

15. Conclusions MW creates similar zones of coagulation necrosis as RF
MW ablation has several theoretical advantages over RF
Larger zone of active heating
Ability to use multiple probes