International Journal of Bioelectronics

Coaxial Slot Antenna Computer Modeling Design for Microwave Ablation in Breast Cancer

Abstract

With the improvements in imaging techniques that have enabled the earlier detection of small breast cancers, a number of minimally invasive treatments for early-stage lesions are being explored. Microwave ablation (MWA) produces dielectric heating by stimulating water molecules within tissues. The aim of this work is to compute the temperature distribution and the frequency-dependent reflection coefficient when using a thin coaxial slot antenna for ablation in breast tissue, using finite element modeling.

Keywords: Breast cancer, Microwave, Ablation.

Introduction

Breast cancer is the most common cancer among women globally. Traditional surgical excision remains the standard of care, yet new thermal-based techniques like laser ablation, focused ultrasound, and microwave ablation offer minimally invasive options. MWA selectively heats high-water-content carcinomas while sparing adipose and glandular tissues. This study presents a computational finite element model (FEM) of a coaxial slot antenna to predict temperature fields and electromagnetic behavior in breast tissue.

Materials and Methods

Microwave frequency was set to 2.45 GHz. The antenna was modeled in COMSOL Multiphysics using an axisymmetric geometry with perfect electric conductor (PEC) boundaries. The Pennes bioheat equation was solved to estimate temperature distribution:

∇·(−k∇T) = ρbCbωb(Tb − T) + Qmet + Qext

where k is thermal conductivity, ρb blood density, Cb specific heat, ωb perfusion rate, and Qext the heat source due to resistive losses. Thermal and electrical properties for breast and tumor tissue were taken from literature and are summarized in Table 1. The antenna operates at 2.45 GHz immersed in homogeneous breast tissue.

Results

The simulated coaxial slot antenna achieved a reflection coefficient of −3.2 dB at 2.45 GHz. Figures 1–4 illustrate the antenna structure, mesh, and resulting temperature distribution. Dense mesh regions were used near the antenna tip to capture concentrated heating effects. The FEM model confirmed focused heat generation within the tumor region and minimal peripheral heating.

Discussion

The coaxial slot antenna model effectively predicts electromagnetic and thermal behavior during MWA. Localized energy deposition enhances precision and minimizes collateral damage. Experimental validation is recommended to confirm computational predictions and optimize antenna parameters for in vivo applications.

References

1. World Cancer Research Fund / American Institute for Cancer Research. Diet, Nutrition, Physical Activity and Cancer: A Global Perspective. 2018.
2. Ekstrand V, Wiksell H, Schultz I, et al. Influence of electrical and thermal properties on RF ablation of breast cancer. Biomed Eng Online. 2005;4:41.
3. Joines WT, Zhang Y, Li C, Jirtle RL. Measured electrical properties of normal and malignant human tissues (50–900 MHz). Med Phys. 1994;21:547–550.
4. Bertram JM, Yang D, Converse MC, Webster JG, Mahvi DM. Antenna design for microwave hepatic ablation using an axisymmetric model. Biomed Eng Online. 2006;5:15.
5. Iskander MF, Tumeh AM. Design optimization of interstitial antennas. IEEE Trans Biomed Eng. 1989;36(2):238–246.
6. Bertram JM, Yang D, Converse MC, Webster JG, Mahvi DM. A review of coaxial-based interstitial antennas for hepatic MWA. Crit Rev Biomed Eng. 2006;34:187–213.
7. Nevels RD, Arndt GD, Raffoul GW, et al. Microwave catheter design. IEEE Trans Biomed Eng. 1998;45:885–890.
8. Wissler EH. Pennes’ 1948 paper revisited. J Appl Physiol. 1998;85(1):35–41.
9. Pennes HH. Analysis of tissue and arterial blood temperatures in the resting human forearm. J Appl Physiol. 1948;1:93–122.
10. Gautherie M. Thermopathology of breast cancer: measurement and analysis of in vivo temperature and blood flow. Ann N Y Acad Sci. 1980;335:383–415.
11. Duck FA. Physical Properties of Tissue. Academic Press, London; 1990.
12. COMSOL AB. RF and Microwave Engineering Module Model Library. COMSOL 5.5; 2019.
13. Guerrero López GD, Cepeda Rubio MFJ, Hernández Jácquez JI, et al. Computational FEM model and ex vivo swine breast validation of an optimized double-slot microcoaxial antenna. Comput Math Methods Med. 2017;2017:1562869.

© 2020 International Journal of Bioelectronics (IJBIOE). Article licensed under CC BY 4.0.