International Journal of Bioelectronics

Slot Type Applicator for the Treatment of Breast Cancer by Microwave Ablation

Abstract

This paper presents the investigation results of thermal microwave ablation therapy for breast cancer treatment. The study was conducted in two stages: first, a computer simulation model predicting therapy effects in different tissues, and second, model validation via experimental therapy using oil, substitute (phantom) tissue, and ex vivo porcine tissue. Results show that this type of therapy holds strong promise as a minimally invasive cancer treatment, though further research and experimentation are required before clinical trials can be performed.

Keywords: Ablation, Breast cancer, Microwave, Finite Element Method, Thermal therapies.

Introduction

Breast cancer remains a leading cause of cancer-related deaths worldwide. While traditional surgery has long been the standard, less invasive techniques such as laser, ultrasound, radiofrequency, and microwave ablation are gaining attention. Microwave ablation (MWA) selectively heats cancerous tissue due to its high water content compared to healthy tissue, producing localized necrosis with lesion size determined by applied power and exposure time. Finite Element Method (FEM) simulations are increasingly used to model physical phenomena, enabling optimization of applicator geometry and design parameters.

MWA Applicator

A slot-type applicator was constructed using semirigid coaxial cable UT-085 with an SMA connector. The applicator was chosen for its simple construction and effective performance reported in earlier works. Design parameters were based on effective wavelength calculations considering heterogeneous tissue properties. Material characteristics and cable dimensions are summarized in Table 1 of the original paper.

Computational Model

Simulations were performed using the Finite Element Method with 2D axisymmetric modeling to represent the 3D geometry. Three media were modeled: vegetable oil, healthy breast tissue, and cancerous breast tissue. The model used a coaxial port excitation at 10 W over a frequency band from 2 to 3.5 GHz. Mesh size was optimized based on effective wavelength for accuracy versus computational time. A mesh of 65,513 elements was used to ensure convergence (see Fig. 3 in the original document).

Experimental Validation

Validation experiments were performed by inserting the applicator into: (1) vegetable oil, (2) cancer-tissue phantom, and (3) ex vivo porcine breast tissue. The phantom was prepared from distilled water, ethanol, NaCl, and agarose, as shown in Table 3 of the original paper. Standing Wave Ratio (SWR) was measured using an Agilent E5071B network analyzer, and temperature was monitored with Luxtron fiber-optic thermometers.

Results and Discussion

Simulation and experimental SWR comparisons showed strong correlation, with minor deviations in low-frequency ranges. In oil and phantom media, SWR values at 2.45 GHz were 5.7 (experiment) and 5.5 (simulation), demonstrating model reliability. Thermal simulations predicted a peak temperature of 93.3 °C, while experiments reached 98 °C in ex vivo tissue. The maximum simulated lesion radius was 6.2 mm, closely matching the experimental 6.1 mm value. Temperature distributions and ex vivo lesions are presented in Figures 9–10 of the paper.

Conclusions

Simulation and experimental results demonstrate that thermal microwave ablation using a slot-type applicator is promising for breast cancer therapy. Lesion sizes predicted through FEM simulations closely matched those observed experimentally. Further refinement of computational models and additional validation in cancerous tissue ex vivo are recommended prior to animal and clinical trials.

References

See full reference list in the original publication (Siegel 2013; Gautherie 1980; Bertram 2006; Lazebnik 2007; COMSOL 2008, and others).

© 2016 International Journal of Bioelectronics (IJBIOE). Article licensed under CC BY 4.0.