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Pre-clinical evaluation of a microwave planar array applicator for superficial hyperthermia
1University of California, Radiation Oncology Department, San Francisco 94143-0226.
Summary
Multi-element microwave applicators offer adjustable power deposition for improved superficial hyperthermia. This system demonstrates flexibility in creating targeted heating patterns, outperforming single-aperture devices for complex tumor geometries.
Area of Science:
- Medical Physics
- Biomedical Engineering
- Thermal Therapy
Background:
- Multi-element hyperthermia applicators allow for adjustable power deposition patterns.
- This capability can compensate for irregular tumor geometry and tissue heterogeneity.
- Single-aperture devices lack this flexibility for precise temperature control.
Purpose of the Study:
- Evaluate the first commercial multi-element microwave system for superficial hyperthermia.
- Assess the system's ability to create adjustable and clinically useful power deposition patterns.
- Compare its advantages over single-aperture devices.
Main Methods:
- Evaluated a 16-element planar array (915 MHz) microwave applicator.
- Measured absolute Specific Absorption Rate (SAR) distributions in phantom models using an E-field sensor.
- Determined power output using calorimetric methods.
Main Results:
- Individual aperture SAR distributions showed significant irregularities and varied power deposition.
- Developed illumination schemes based on known deposition characteristics.
- Demonstrated adjustable composite patterns with 50% iso-SAR coverage extending to the perimeter.
Conclusions:
- The multi-element applicator offers adjustable and flexible heating capabilities.
- This system shows significant clinical utility and advantages over single-aperture devices for superficial hyperthermia.
- The ability to tailor power deposition is crucial for treating complex thermal targets.