Frequency optimization of focused microwave hyperthermia applicators

Ling, Hao; Lee, Shung-Wu; Gee, W.

doi:10.1109/proc.1984.12844

Cited by 22 publications

(2 citation statements)

References 2 publications

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“…Additionally, the focality of our proposed methodology is lower than the millimeter level specificity of DBS devices. Our future work will use systematic algorithmic optimization of the two arrays' locations [52] and the choice of frequency [53][54][55] to potentially achieve high EMvelop stimulation intensity and focality values. Other ways to improve focality include increasing the size of the array [21] or harnessing unconventional antenna patterns created by the non-adjacent placement of the antenna elements in an array [56].…”

Section: Conclusion and Discussionmentioning

confidence: 99%

EMvelop stimulation: minimally invasive deep brain stimulation using temporally interfering electromagnetic waves

et al. 2022

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Objective. Recently, the temporal interference stimulation (TIS) technique for focal noninvasive deep brain stimulation (DBS) was reported. However, subsequent computational modeling studies on the human brain have shown that while TIS achieves higher focality of electric fields than state-of-the-art methods, further work is needed to improve the stimulation strength. Here, we investigate the idea of EMvelop stimulation, a minimally invasive DBS setup using temporally interfering gigahertz (GHz) electromagnetic (EM) waves. At GHz frequencies, we can create antenna arrays at the scale of a few centimeters or less that can be endocranially implanted to enable longitudinal stimulation and circumvent signal attenuation due to the scalp and skull. Furthermore, owing to the small wavelength of GHz EM waves, we can optimize both amplitudes and phases of the EM waves to achieve high intensity and focal stimulation at targeted regions within the safety limit for exposure to EM waves. Approach. We develop a simulation framework investigating the propagation of GHz EM waves generated by line current antenna elements and the corresponding heat generated in the brain tissue. We propose two optimization flows to identify antenna current amplitudes and phases for either maximal intensity or maximal focality transmission of the interfering electric fields with EM waves safety constraint. Main results. A representative result of our study is that with two endocranially implanted arrays of size 4.2 cm × 4.7 cm each, we can achieve an intensity of 12 V/m with a focality of 3.6 cm at a target deep in the brain tissue. Significance. In this proof-of-principle study, we show that the idea of EMvelop stimulation merits further investigation as it can be a minimally invasive way of stimulating deep brain targets and offers benefits not shared by prior methodologies of electrical or magnetic stimulation.

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Section: Conclusion and Discussionmentioning

confidence: 99%

EMvelop stimulation: minimally invasive deep brain stimulation using temporally interfering electromagnetic waves

et al. 2022

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“…1(a)) with a specific type, such as horn [17], dipole antenna [19][20][21], or electric current filaments [22,23], which prevents the results from being the global optimum. Since any physical antenna has an inherent dependency on frequency, the optimal frequency obtained over a confined source domain cannot be claimed as the global optimum, either [19][20][21]24]. As a result, currently, various types of sources are employed in practice with their operating frequency lying from a low megahertz to a gigahertz range [16,25] in the lack of convincing arguments that which one should yield the global optimum.…”

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confidence: 99%

Institute for Laser Engineering, Kyung Hee University

Lee¹,

Park²

2001

The Review of Laser Engineering

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Microwave ablation is a therapeutic procedure to eliminate abnormal tissue within a body selectively. There are two types of ablations; the thermal one aims to raise the temperature at the target, while the non-thermal one induces a temporarily high electric field at the target to disrupt cellular membrane integrity. This work identifies the fundamental bounds of the efficiency for each type of ablation and the sources to achieve them. For both types, the bounds exceed the performance of existing solutions by tenfold, showing a large room for improvement. Finally, the optimal source for thermal ablation is physically realized with an 11 × 11 dipole array, the performance of which closely approaches the bound.

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