Coaxial Slot Antenna Design for Microwave Hyperthermia using Finite- Difference Time-Domain and Finite Element Method

Abstract

Hyperthermia also called thermal therapy or thermotherapy is a type of cancer treatment in which body tissue is exposed to high temperatures. Research has shown that high temperatures can damage and kill cancer cells, usually with minimal injury to normal tissues. Otherwise, ablation or high temperature hyperthermia, including lasers and the use of radiofrequency, microwaves, and high-intensity focused ultrasound, are gaining attention as an alternative to standard surgical therapies. The electromagnetic microwave irradiation applied to the tumor tissue causes water molecules to vibrate and rotate, resulting in tissue heating and subsequently cell death via thermal-induced protein denaturation. The effectiveness of this technique is related to the temperature achieved during the therapy, as well as the length time of treatment and cell and tissue characteristics. Numerical electromagnetic and thermal simulations are used to optimize the antenna design and predict heating patterns. A computer modeling of a double slot antenna for interstitial hyperthermia was designed using two different numerical methods, the Finite Element Method and a Finite-Difference Time-Domain. The aim of this work is to analyze both numerical methods and finally experiments results are compared to the simulated results generated by a thermal model. Our results show that normalized SAR patterns using FEM and FDTD look broadly similar. Furthermore, the computed 60 °C isotherm using FEM and the measured lesion diameter in ex vivo tissue results agree very well.

Heat Transfer Study in Breast Tumor Phantom during Microwave Ablation: Modeling and Experimental Results for Three Different Antennas

“…Moreover, its hard-mathematical formulation allows for solving complex models with a high degree of accuracy. Although the FDTD method can be considered a feasible way to model the wave propagation through different mediums, it needs a lot of computational resources, especially in the design process [35,37,38]. The finite element method (FEM) is a numerical technique that can be formulated as a functional minimization.…”

“…Electric and thermal tissue properties (healthy and tumor breast) are shown in Table 1, as well as blood parameters, relative permittivity for the dielectric of the antenna and for the catheter, microwave frequency, and input power used for the FEM models [35]. Tissues' dielectric properties at 2.45 GHz were obtained from [43].…”

“…Figure 1b depicts the double coaxial antenna design. In the case of the applicator inserted in the tumor tissue surrounded by breast tissue, it had an SWR of 1.85, calculated at 2.45 GHz, while the simulated SWR was 2.94 for the antenna surrounded by tumor tissue [35]. Finally, the design of the double short-distance slot antenna was optimized by a parametric study.…”

Feasibility of Using a Novel 2.45 GHz Double Short Distance Slot Coaxial Antenna for Minimally Invasive Cancer Breast Microwave Ablation Therapy: Computational Model, Phantom, and In Vivo Swine Experimentation

“…This cable has a center conductor diameter of 0.51 mm, an outer conductor diameter of 2.20 mm, and a dielectric diameter of 1.68 mm. The antenna was encased in a polytetrafluoroethylene (PTFE) catheter (2.58 mm) to avoid adhesion of the antenna to ablated tissue [ 18 ]. The double short distance slot antenna was modeled and optimized.…”

Electromagnetic hyperthermia on porous model of hepatic cancerous tissue

“…Numerous engineering simulation studies parallel with clinical trials have been focused on the hyperthermic oncological treatment of different types of cancer, including sarcoma, melanoma, cancers of the head and neck, brain, lung, esophagus, breast, bladder, rectum, liver, kidney, bone, appendix, cervix, and peritoneal lining to predict the outcome of treatment, minimize healthy tissue damage, optimize ablation procedure, and totally make treatment simple, safe, and effective more and more. It is still essential to discover the different aspects of hyperthermic oncological treatments more precisely and share them with medical doctors in order to increase the effects of these cures.…”