Abstract
Electromagnetic hyperthermia as a potent adjuvant for conventional cancer therapies can be considered valuable in modern oncology, as its task is to thermally destroy cancer cells exposed to high-frequency electromagnetic fields. Hyperthermia treatment planning based on computer in silico simulations has the potential to improve the localized heating of breast tissues through the use of the phased-array dipole applicators. Herein, we intended to improve our understanding of temperature estimation in an anatomically accurate female breast phantom embedded with a tumor, particularly when it is exposed to an eight-element dipole antenna matrix surrounding the breast tissues. The Maxwell equations coupled with the modified Pennes’ bioheat equation was solved in the modelled breast tissues using the finite-difference time-domain (FDTD) engine. The microwave (MW) applicators around the object were modelled with shortened half-wavelength dipole antennas operating at the same 1 GHz frequency, but with different input power and phases for the dipole sources. The total input power of an eight-dipole antenna matrix was set at 8 W so that the temperature in the breast tumor did not exceed 42 °C. Finding the optimal setting for each dipole antenna from the matrix was our primary objective. Such a procedure should form the basis of any successful hyperthermia treatment planning. We applied the algorithm of multi for multi-objective optimization for the power and phases for the dipole sources in terms of maximizing the specific absorption rate (SAR) parameter inside the breast tumor while minimizing this parameter in the healthy tissues. Electro-thermal simulations were performed for tumors of different radii to confirm the reliable operation of the given optimization procedure. In the next step, thermal profiles for tumors of various sizes were calculated for the optimal parameters of dipole sources. The computed results showed that larger tumors heated better than smaller tumors; however, the procedure worked well regardless of the tumor size. This verifies the effectiveness of the applied optimization method, regardless of the various stages of breast tumor development.
Highlights
Neoplastic diseases and the growing number of deaths caused by them is a challenging major global health issue [1]
The most common lumps develop in glandular tissue, in the upper side of the breast (35% of cases), and less often in the medial part (5%)
Due to the dimension limitations around a female breast, we selected the 1-GHz shortened-length dipole antennas for the EM excitations, whose phases and powers were changed while maintaining an unchanged power of 8 W for the entire dipole matrix
Summary
Neoplastic diseases and the growing number of deaths caused by them is a challenging major global health issue [1]. Phased arrays often utilize optimization procedures in line with the specific absorption rate (SAR) parameter, whereby the amplitude, phase, or frequency of the excitation signal produced by monopole antennas [18], dipole antennas [19,20], patch antennas [21], or more complex applicators [22] can be adjusted They operate in broadband (treatment of surface tumors) [16] or narrowband regimes (treatment of deep-seated tumors) [23] at one or more frequencies [18]. The current paper omits the technical aspects of supplying individual dipole antennas, focusing only on the optimization of their basic parameters, in terms of the phase and input power, in order to achieve optimal treatment of breast tumors through the thermal effects of MW radiation. Various techniques for hyperthermia treatment have been developing rapidly Their effectiveness continues to increase, especially when combined with other anti-cancer modalities [3,16]. Combination therapies can be utilized to induce tumor size reduction before surgery (preoperative therapies) or remove any surviving malignant cells after surgery and reduce the risk of cancer recurrence (postoperative therapies) [40]
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