Thermal energy deposition from a single-loop rf whole-body applicator

Area of Science:

• Biomedical Engineering
• Hyperthermia Therapy
• Radiofrequency (RF) Applications

Background:

• Whole-body hyperthermia (WBH) at moderate temperatures (40.0 ± 0.5°C) is explored as an adjuvant cancer therapy.
• Institutional WBH utilizes combined hot air circulation and 27.1 MHz RF inductive heating.
• Understanding RF applicator thermal energy deposition is crucial for optimizing WBH protocols.

Purpose of the Study:

• To investigate the thermal energy deposition pattern of a specific RF applicator used for WBH.
• To analyze the contributions of magnetic induction and capacitive fields to heating.
• To assess the implications of heating patterns for tissue selectivity, particularly fatty tissues.

Main Methods:

• Utilized a 20 x 46 cm elliptical RF loop applicator embedded in a mattress.
• Performed temperature mapping in a gelatin phantom positioned above the RF loop.
• Conducted calculations to differentiate between magnetically induced and capacitive electric field contributions.

Main Results:

• Observed maximum heating near the lead wire entry points and a cooler central region above the RF loop.
• Determined that heating near lead wires is predominantly capacitive.
• Calculations indicated that capacitive heating decreases more rapidly with distance from the loop than induced field heating.

Conclusions:

• The RF applicator exhibits non-uniform heating, with localized intense heating near lead wires.
• The capacitive nature of heating near lead wires suggests preferential heating of fatty tissues.
• Further research is needed to optimize applicator design and heating protocols for uniform and targeted WBH.