Low-frequency RF hyperthermia: IV--A 27 MHz hybrid applicator for localized deep tumor heating

Area of Science:

• Medical Physics
• Biomedical Engineering
• Radiofrequency Ablation

Background:

• Noninvasive tumor heating requires precise energy deposition.
• Conventional radiofrequency (RF) applicators face limitations in achieving deep and localized heating.
• Improving safety and efficacy in hyperthermia cancer treatment is a key research area.

Purpose of the Study:

• To propose and assess a novel 27 MHz dual-device applicator for safe, noninvasive deep tumor heating.
• To investigate the potential of superimposed RF currents for localized thermal effects.
• To evaluate the performance of a hybrid applicator integrating capacitive and inductive heating.

Main Methods:

• Development of a hybrid applicator (HA) with capacitive and inductive RF devices.
• Assessment of the HA on a cylindrical fat-muscle phantom (20 cm diameter).
• Characterization of the specific absorption rate (SAR) interference pattern and temperature distribution.

Main Results:

• Achieved a substantially localized temperature gain via constructive interference of two RF current distributions.
• Demonstrated a deep, broad SAR maximum, eliminating the null SAR typical of single inductive devices.
• Obtained an 80% SAR useful therapeutic volume (UTV) of approximately 800 cm3 with 6-8 cm penetration.

Conclusions:

• The novel dual-device applicator offers improved safety and efficacy for noninvasive deep tumor heating.
• The hybrid applicator design enables controllable UTV size and penetration depth.
• Uniform safe heating of surrounding tissues at a sub-therapeutic temperature pedestal was achieved with reduced RF power.