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. 2017:2017:5787484.
doi: 10.1155/2017/5787484. Epub 2017 Aug 1.

Enhanced Energy Localization in Hyperthermia Treatment Based on Hybrid Electromagnetic and Ultrasonic System: Proof of Concept with Numerical Simulations

N Nizam-Uddin  1 , Ibrahim Elshafiey  1
Affiliations

Enhanced Energy Localization in Hyperthermia Treatment Based on Hybrid Electromagnetic and Ultrasonic System: Proof of Concept with Numerical Simulations

N Nizam-Uddin et al. Biomed Res Int. 2017.

Abstract

This paper proposes a hybrid hyperthermia treatment system, utilizing two noninvasive modalities for treating brain tumors. The proposed system depends on focusing electromagnetic (EM) and ultrasound (US) energies. The EM hyperthermia subsystem enhances energy localization by incorporating a multichannel wideband setting and coherent-phased-array technique. A genetic algorithm based optimization tool is developed to enhance the specific absorption rate (SAR) distribution by reducing hotspots and maximizing energy deposition at tumor regions. The treatment performance is also enhanced by augmenting an ultrasonic subsystem to allow focused energy deposition into deep tumors. The therapeutic faculty of ultrasonic energy is assessed by examining the control of mechanical alignment of transducer array elements. A time reversal (TR) approach is then investigated to address challenges in energy focus in both subsystems. Simulation results of the synergetic effect of both modalities assuming a simplified model of human head phantom demonstrate the feasibility of the proposed hybrid technique as a noninvasive tool for thermal treatment of brain tumors.

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Figures

Figure 1
Figure 1
(a) Perspective view of the proposed multichannel wideband hyperthermia treatment incorporated with different head tissue layers; (b) side view indicating the arrangement of ports; (c) front view indicating the location of the tumor at top right.
Figure 2
Figure 2
Frequency response of human brain tissue in terms of (a) real permittivity and (b) imaginary permittivity values.
Figure 3
Figure 3
Ultrasound hyperthermia model of human head with embedded tumor at top right with (a) 8 transducers and (b) 256 transducers.
Figure 4
Figure 4
Variation of cost function in terms of phase and magnitude.
Figure 5
Figure 5
E-field map of excitation ports numbered 1–4 (left to right) for different subcarriers (top to bottom).
Figure 6
Figure 6
E-field map of excitation ports numbered 5–8 (left to right) for different subcarriers (top to bottom).
Figure 7
Figure 7
E-field map of EM energy propagating towards the tumor when ports 1–4 from left to right are excited by frequency subcarriers of 1, 1.5, 2, and 2.5 GHz, respectively.
Figure 8
Figure 8
E-field map of EM energy propagating towards the tumor when ports 5–8 from left to right are excited by frequency subcarriers of 3, 2.75, 0.75, and 0.5 GHz, respectively.
Figure 9
Figure 9
The capability of coherent-phased-array tool to localize energy for (a) zero phase shift, (b) inappropriate phase shift, and (c) appropriate phase shift when frequency of operation is 0.5 GHz.
Figure 10
Figure 10
SAR optimization for the narrowband case when frequency is (a) 0.5 GHz, (b) 1 GHz, (c) 2 GHz, and (d) 3 GHz.
Figure 11
Figure 11
SAR optimization for the wideband (0.3–3 GHz) case.
Figure 12
Figure 12
TR focusing for EM hyperthermia in (a) xy, (b) xz, and (c) yz planes when frequency of operation is 0.5 GHz.
Figure 13
Figure 13
Single transducer insonation for different frequencies: (a) 0.05 MHz, (b) 0.1 MHz, and (c) 0.5 MHz.
Figure 14
Figure 14
(a) Acoustic field intensity in the absence of skull-bone layer and (b) the corresponding pressure at axial distance through the head center at 0.05 MHz.
Figure 15
Figure 15
(a) Acoustic field intensity in the absence of skull-bone layer and (b) the corresponding pressure at axial distance through the head center at 0.1 MHz.
Figure 16
Figure 16
(a)Acoustic field intensity in the absence of skull-bone layer and (b) the corresponding pressure at axial distance through the head center at 0.5 MHz.
Figure 17
Figure 17
(a) Acoustic field intensity in the presence of skull-bone layer and (b) the corresponding pressure at axial distance through the head center at 0.05 MHz.
Figure 18
Figure 18
(a) Acoustic field intensity in the presence of skull-bone layer and (b) the corresponding pressure at axial distance through the head center at 0.1 MHz.
Figure 19
Figure 19
(a) Acoustic field intensity in the presence of skull-bone layer and (b) the corresponding pressure at axial distance through the head center at 0.5 MHz.
Figure 20
Figure 20
Localization of acoustic energy at the tumor center using two transducers with a mechanical approach.
Figure 21
Figure 21
Step 1 of TR localization for US hyperthermia when a monopole source is excited with frequencies of (a) 0.05 MHz, (b) 0.1 MHz, and (c) 0.5 MHz each normalized to 1 MPa.
Figure 22
Figure 22
Step 2 of TR localization for US hyperthermia when acoustic energy from transducers is back-propagated towards the tumor with frequencies of (a) 0.05 MHz, (b) 0.1 MHz, and (c) 0.5 MHz.
Figure 23
Figure 23
Variation in thermal intensity (normalized) at the tumor center for different time insonations, (a) 2 sec, (b) 6 sec, (c) 10 sec, and (d) 14 sec, for mechanical alignment focusing approach.
Figure 24
Figure 24
Thermal response (log scale) of the proposed US hyperthermia module based on TR focusing approach.
Figure 25
Figure 25
Normalized temperature profiles of (a) EM hyperthermia module and (b) ultrasound hyperthermia module based on time reversal (TR) localization.
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