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Radio-frequency ring applicator: energy distributions measured in the CDRH phantom
G C van Rhoon1, P Raskmark, S N Hornsleth
1Department of Hyperthermia, Dr. Daniel den Hoed Cancer Center, Rotterdam, The Netherlands.
Medical & Biological Engineering & Computing
|November 1, 1994
Summary
This study demonstrates a ring applicator for deep hyperthermia. It achieved uniform specific absorption rate (SAR) distributions at 30 MHz and improved focusing at 70 MHz, showing feasibility for targeted tissue heating.
Area of Science:
- Biomedical Engineering
- Electromagnetics
- Medical Physics
Background:
- Deep hyperthermia requires precise control of radio-frequency (RF) energy deposition.
- Current applicators face challenges in achieving targeted heating in deep tissues.
Purpose of the Study:
- To evaluate the feasibility of a novel ring applicator for deep hyperthermia.
- To assess the specific absorption rate (SAR) distributions generated by the applicator.
- To demonstrate control over RF energy deposition for targeted heating.
Main Methods:
- Measurements of SAR distributions were performed in a CDRH phantom simulating human abdomen.
- A ring applicator with eight feeding points was used, with deionized water as the coupling medium.
- An E-field probe measured SAR in three directions, with varying amplitude and phase at feeding points and frequencies of 30 MHz and 70 MHz.
Main Results:
- Uniform SAR distribution was achieved in the central cross-section at 30 MHz with equal amplitude and phase.
- Amplitude steering was demonstrated at 30 MHz, concentrating SAR in one quadrant.
- Improved focusing ability was observed at 70 MHz, with SAR maxima at the center for specific tissue conductivities (0.6 and 0.4 S m-1).
Conclusions:
- The ring applicator is feasible for deep hyperthermia applications.
- The applicator allows for control over SAR distribution through amplitude steering and frequency selection.
- Optimized focusing at 70 MHz suggests potential for precise deep tissue heating.