Multiprobe RF ablation: A Feasibility Study
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Multiprobe RF ablation: A Feasibility Study
Fred T. Lee Jr., MDDieter Haemmerich, MSAndrew S. Wright, MDDavid M. Mahvi, MDJohn G. Webster, PhD
University of Wisconsin Depts. Of Radiology, Bioengineering, Surgery
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Why multiprobe RF?
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Why multiprobe RF?
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Why multiprobe RF?
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Why multiprobe RF?
• Simultaneous ablations– Increase lesion number– Multiple probes in large tumor
• Decrease ablation time• Improve temperature distribution in lesion
(make ablation more effective)• Control lesion (bigger not always better)
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Current RF systems
• Multiple prongs run at same voltage
RITA
RTC
Radionics
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Faraday Effect
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Faraday Effect
Electrodes at same voltage
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Faraday Effect
Probes at different voltage=bipolar Current flows between probes
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Faraday Effect
Electrically independent probes
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How independent probes created
• Rapid switching between probes• Temperature in tissue changes much
slower than switching• Temperature/impedance feedback
algorithm
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How independent probes created
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Prototype dual probe unit
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Prototype dual probe unit
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Ex vivo results: Dual probes in pig liver at same temperature
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In vivo results
• Domestic pigs (n=3, mean wt=35 kg)• 13 RF lesions
– 3 single control lesions– 10 dual (5 pairs created simultaneously)
RITA Model 150 generator (150 W), Starburst electrode deployed to 3.0 cm. 10 minute ablation, 100° C.
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In vivo results
vs
Single Simultaneous dual RF
Note: same scale
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In vivo results
• Time to temperature (100°C)single: 2.7 minutes (162
seconds)dual: 3.4 minutes (204 seconds)
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In vivo results:volume of necrosis
• Single: 10.7 cc• Dual (each individual lesion): 17.3ccTherefore, 34.6 cc ablation obtained in
approximately same time as 10.7 cc ablation
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In vivo results:max diameter
• Single: 3.3 cm• Dual (each individual lesion): 3.8 cm
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Conclusions
• Feasible to create multiple simultaneous burns with a single generator
• No lesion size penalty• Slight increase in time to
temperature
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What’s next?
• Increase # of probes (?4)• Will require increased generator power• Many technical factors involved with rapid
switching (mechanical electrical)• Cluster probes in close proximity to
increase lesion size, temperature