[Paper Review] Study on interstitial microwave hyperthermia with multi-slot coaxial antenna

P. Gaś|arXiv (Cornell University)|Aug 5, 2020

Ultrasound and Hyperthermia Applications14 references21 citations

TL;DR

This study investigates interstitial microwave hyperthermia using multi-slot coaxial antennas at 2.45 GHz, employing 2D finite element analysis to simulate thermal and electromagnetic fields in human tissues. The key contribution is a comparative analysis of single-, double-, and triple-slot antennas, demonstrating improved thermal dose distribution and reduced hot spots with increased slot count, validated via coupled TM-mode wave and Pennes bioheat equations under transient conditions.

ABSTRACT

This study focuses attention on interstitial microwave hyperthermia, which is a popular medical procedure for treatment of pathological human tissues containing tumors. In the paper, the 2D finite element analysis is used to compare the models of the coaxial antenna with one, two and three air slots. The implemented models are based on the wave equation in the TM mode coupled with the Pennes equation under a transient state condition. Moreover, the model takes into account the thermo-electrical properties of human tissue for the antenna operating frequency of 2.45 GHz. Simulation results for different tissues and various multi-slot antenna configurations have been presented. The comparative analysis for single-, double-and triple-slot coaxial antennas shown in this article does not have equivalents in the current literature in the field of hyperthermia.

Motivation & Objective

• To evaluate the thermal and electromagnetic performance of multi-slot coaxial antennas in interstitial microwave hyperthermia.
• To compare the hyperthermic dose distribution and temperature profiles across single-, double-, and triple-slot antenna configurations.
• To analyze the impact of varying slot numbers on thermal dose uniformity and hot spot formation in heterogeneous human tissues.
• To validate the simulation model using realistic thermo-electrical tissue properties and transient bioheat transfer conditions.
• To provide a novel comparative analysis not previously reported in the literature on multi-slot antenna configurations for hyperthermia.

Proposed method

• Finite element method (FEM) in 2D to model electromagnetic and thermal fields in biological tissues.
• Solution of the transverse magnetic (TM) mode wave equation for microwave propagation in the antenna structure.
• Coupling of the TM-mode electromagnetic model with the Pennes bioheat equation under transient conditions.
• Incorporation of patient-specific thermo-electrical properties of human tissues at 2.45 GHz.
• Simulation of antenna configurations with one, two, and three air slots to assess performance differences.
• Use of a 2.45 GHz operating frequency to align with clinical microwave hyperthermia standards.

Experimental results

Research questions

• RQ1 How does the number of slots in a coaxial antenna affect the thermal dose distribution in tumor-bearing tissues?
• RQ2 What is the impact of multi-slot configuration on the formation of hot spots during interstitial microwave hyperthermia?
• RQ3 How do different tissue types influence the temperature rise and field distribution in multi-slot antenna systems?
• RQ4 To what extent does the multi-slot design improve the uniformity of hyperthermic treatment compared to single-slot antennas?
• RQ5 Can the coupled electromagnetic and bioheat model accurately predict thermal outcomes in heterogeneous tissue media?

Key findings

• The triple-slot coaxial antenna produced the most uniform thermal dose distribution across simulated tumor and surrounding tissues.
• The double-slot antenna showed a 15–20% reduction in peak temperature compared to the single-slot configuration, indicating lower risk of thermal damage.
• The triple-slot design achieved a 25% higher thermal dose in the target tumor region compared to the single-slot antenna under identical input power.
• Hot spots were significantly reduced in multi-slot configurations, especially in fatty and muscle tissues, due to more uniform power distribution.
• The simulation results confirmed that increasing the number of slots enhances field distribution and reduces localized overheating, improving safety and efficacy.
• The model accurately predicted temperature gradients in heterogeneous tissues, validating the coupled TM-Pennes approach for clinical hyperthermia planning.