Hepatic Microwave Ablation with Multiple Antennae Results in Synergistically Larger Zones of Coagula

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Hepatic Microwave Ablation with Multiple Antennae
Results in Synergistically Larger Zones of
Coagulation Necrosis

• Andrew Wright MD1, Fred Lee Jr. MD2, and David
  Mahvi MD1

Departments of Surgery1 and Radiology2 University
of Wisconsin Hospital
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Rationale for Hepatic Ablation

• Resection is gold standard for hepatic tumors
• Hepatic tumor ablation increases the number of
  patients eligible for curative therapy
• Types of therapy
• Radiofrequency ablation
• Cryotherapy

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Microwave Ablation

• Microwave energy applied through antenna placed
  into tumor
• Clinical use in Asia
• Limited by feedback of microwave energy
• Short duration of application
• Small ablation lesions

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Microwave Ablation

• Prototype Microwave Ablation System
• Antenna designed to match tissue characteristics
  of liver
• Reduced feedback
• Better control and larger lesions

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Microwave Ablation

• Theoretical advantages over radiofrequency
  ablation
• Broad Field of Power Distribution

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Microwave Ablation

• Theoretical advantages over radiofrequency
  ablation
• Broad Field of Power Distribution
• High Temperature

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Microwave Ablation

• Theoretical advantages over radiofrequency
  ablation
• Broad Field of Power Distribution
• High Temperature
• Use of Multiple Probes

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Multiple Probe Microwave Ablation

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

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Hypothesis

• Sequential multiple probe hepatic ablation will
  create larger zones of coagulation necrosis than
  single probe ablation, due to the additive effect
  of creating multiple overlapping lesions

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Hypothesis

• Simultaneous multiple probe microwave ablation
  will create synergistically larger lesions than
  either single probe or sequentially-activated
  multiple probe ablation, due to shielding of the
  lesion center from blood-flow mediated cooling

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Microwave Ablation

• Microwave Ablation System

Vivant Medical 13 gauge, 15 cm dipole
antenna 60 W, 915 MHz generator 8 channels
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Methods

• In vivo porcine model
• Single Probe Ablation (n11)

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Methods

• Multiple Probe Ablation

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Methods

• Multiple Probe Ablation
• Sequential (n11)
• Simultaneous (n13)
• Separation between probes varied between 0.5 and
  3 cm

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Assessment

• Lesions sectioned at 3 mm intervals
• Digital image recorded of each section at 300 dpi
• Lesion dimensions calculated using ImageJ
  analysis software

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Assessment

• Multiple Probe lesions scored for shape

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Assessment

• Lesion Shape

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Results
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Results
Sequential Multiple Probe
Single Probe
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Results
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Results
Sequential Multiple Probe
Single Probe
Simultaneous Multiple Probe
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Results
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Results
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Results

• Lesion Shape

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Results

• Lesion Shape

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Results

• Lesion Shape

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Results
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Results

• 5 Probes

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Conclusions

• Simultaneous multiple probe microwave ablation
  may improve treatment of tumors near blood
  vessels
• Permits simultaneous treatment of multiple tumors
• Decreased time of procedure

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Conclusions

• Simultaneous multiple probe ablation results in
  synergistically larger lesions than sequential or
  single probe ablation
• Twice as large as sequential and nearly six times
  larger than single probe ablation

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Conclusions

• Simultaneous multiple probe ablation may allow
  for better treatment of large tumors that require
  multiple, overlapping lesions
• Increased lesion size
• Improved control over lesion size and shape
• Superior lesion geometry