Efficient energy localization for hybrid wideband hyperthermia
Electrical Engineering Department, King
Saud University, Riyadh, Saudi Arabia
Nizam Uddin, Electrical Engineering
Department, King Saud University,
Riyadh, Saudi Arabia.
King Abdul-Aziz City for Science and
Technology (KACST), General
Administration for Research Grants
Grant/Award Number: AT 35-210.
This article presents efficient energy localization approach for hybrid wideband sys-
tem for hyperthermia treatment of cancer based on a transmission line (TL). A
heterogeneous head phantom is built by incorporating frequency dependent tissue
properties of head layers considering both electromagnetic and ultrasound treatment.
Effective medium properties are derived and used to compensate signal phase and
magnitude values based on TL model. The obtained field map results emphasize the
feasibility of the developed approach to obtain system parameters that enhance energy
localization and eradicate hotspots.
energy localization, hyperthermia treatment, SAR, transmission line model, wideband system
Hyperthermia has emerged as a promising modality for cancer
therapy. During hyperthermia treatment (HT), the temperature
of the malignant tissues is raised to 408C-458C using either
EM or ultrasound (US) energy.
When used in adjunct with
radiotherapy and chemotherapy, HT can increase the efficacy
of therapeutic plans.
The increase of temperature during
hyperthermia is correlated to the specific absorption rate
(SAR), which depends upon various factors including tissue
properties, the number of heating sources, the biological inter-
action of EM or US energy with human tissue, the size and
location of tumor and the frequency of operation.
One of the
main challenges in clinical hyperthermia is to heat deep-seated
tumor without damaging the surrounding healthy tissue. Math-
ematically, it requires SAR optimization to meet this challenge.
Several techniques have been reported in recent research
regarding SAR optimization in EM hyperthermia systems,
inverse multiphysics strategy,
particle swarm optimization.
When compared with EM
fields, acoustic energy propagates with reduced speed and
shorter wavelength values can be useful to target small-sized
tumors with deep penetration. EM fields on other hand have
wide wavefront and are capable of targeting larger areas. US
fields also face a problem in noninvasive transcranial energy
delivery compared with EM fields because of the high US
impedance of skull-bone.
This research aims to enhance energy localization at the
tumor site. System degrees of freedom are increased by
assuming multiport excitation, hybrid energy and wideband
operating system. Parameter optimization is based on simple
transmission-line TL model. Cascaded TLs are used to repre-
sent signal delay in different tissues. Effective permittivity
values of the mediums are estimated by comparing results of
the simplified TL model with results of 3D energy interac-
tion model. A technique is also developed to nullify the
phase aberrations for the case of US hyperthermia caused by
the skull-bone layer.
To investigate the feasibility of wideband HT, a numeri-
cal head phantom model of radius 10 cm is built using CST
This cylindrical phantom is composed
of tissue representing brain enclosed by 0.5-cm thickness of
skull. A tumor of radius 2.5 cm is located at x 5 3cm,
y 5 4 cm and z 5 0 cm as shown in Figure 1A,B. Eight
energy applicator ports surround the phantom. The amplitude
and phase of the signal at excitation port is depicted in Figure
1C,D respectively. To ensure minimum reflections at the
boundaries, open boundary conditions are selected for this
Int J RF Microw Comput Aided Eng. 2018;28:e21238.
2018 Wiley Periodicals, Inc.
Received: 3 August 2017
Revised: 31 December 2017
Accepted: 31 December 2017