1. Andrew Wright MD, Chris Johnson, Fred Lee Jr. MD, and David Mahvi MD
Microwave Ablation of Hepatic Tumors: Simultaneous Use of Multiple Probes Results in Large Areas of Tissue Necrosis
Andrew Wright MD, Chris Johnson, Fred Lee Jr. MD, and David Mahvi MD
Departments of Radiology and Surgery
University of Wisconsin Hospital

2. Multiple Probe Ablation
Microwave Ablation
Goals
Increase lesion size
Increase control and customization of lesion size and shape
Decrease treatment time
Allow for treatment of multiple tumors

3. Hypothesis
Multiple probe hepatic ablation will result in synergistically larger lesion sizes by shielding lesion center from blood-flow mediated cooling

4. Methods Microwave Ablation System • Vivant Medical
3.6cm length of actively radiating antenna
• Vivant Medical
• 13g, 15cm dipole antenna
• 60W, 915MHz generator
• 8 channels
• Fiberoptic temperature monitor

5. Methods Microwave Protocol Domestic Swine 10 minute ablation, 40 Watts
Single Probe Ablation
Multiple Probe Ablation
3 parallel probes in triangular array
Separation between probes varied from 0.5 to 3.5cm

6. Methods
Microwave Protocol
Single Probe
Multiple Probe

7. Assessment Lesion dimensions calculated
Multiple Probe lesions scored for shape
Score
Criteria 1
Discontinuous 2
>25% Deflection 3
10-25% Deflection 4
<10% Deflection 5
Round

8. Results

9. Results
Single: 2.3  0.5
Multiple: 4.8  1.0

10. Results
Single: 11.5  7.8
Multiple: 42.2  17.4

11. Results
Size by Separation

12. Results
Lesion Shape

13. Results
Lesion Shape

14. Results
Temperature
Max T:
Single 124oC
Multiple 147oC

15. Results

16. Results
5 Probes

17. Conclusions
Microwave ablation may be performed with multiple, simultaneous probes
Microwave ablation with three probes results in lesions four times larger than single probe microwave ablation
Confluent lesions may be produced with probe separations of 1.6cm or less

18. Summary
Microwave ablation has several theoretical advantages over RF ablation
Multiple probe microwave ablation may allow for treatment of larger, more complex tumors as well as simultaneous treatment of multiple tumors
Multiple probe ablation may improve treatment of tumors near blood vessels