FDTD analysis of power deposition patterns of an array of interstitial antennas for use in microwave hyperthermia

Cherry, P.C.; Iskander, Magdy F.

doi:10.1109/22.149549

Cited by 27 publications

(9 citation statements)

References 20 publications

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“…The evaluation of the gradients in the above expression can be accomplished in an efficient manner by manipulating (18) to arrive at (20) (21) where and denote the real and imaginary parts of their arguments, respectively, and is a vector consisting of all zeros, except for one in the position corresponding to . It is assumed that the discrete positions ( ) involved in the computation of the performance index coincide with points at which the temperature field is known from the FD-BHTE ( ).…”

Section: B Numerical Modeling and Optimizationmentioning

confidence: 99%

“…If detailed highly accurate temperature information is required, this number could be even larger. Table II evidences the savings in computation time made possible by precomputing the 16 basis temperatures and superposing them via (18), (20), and (21) to evaluate the objective function and its gradients (referred to as the superposition method in the table) rather than resolving the FD-BHTE system for each function and gradient evaluation (referred to as the direct method in the table). In practice, it was found that for a relative functional tolerance of 10 , 10-20 iterations of the CG are needed for convergence of the optimization problem.…”

Section: B Three-dimensional Analysis Of a Phantommentioning

confidence: 99%

“…The use of the FDTD in hyperthermia treatment planning has been widely reported [18]- [21] and validation of the predictions made by the FDTD in this context has been performed [22]. Since the FDTD has modest computational requirements, a full three-dimensional model of the patient and applicators can easily be simulated.…”

Section: Introductionmentioning

confidence: 99%

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Determination of electromagnetic phased-array driving signals for hyperthermia based on a steady-state temperature criterion

Kowalski

Jin

2000

IEEE Trans. Microwave Theory Techn.

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Electromagnetic phased arrays can be used to preferentially heat tumors, potentially providing clinical benefit in oncological applications. Synthesizing a temperature field that exposes cancerous cells to sufficiently elevated temperatures while not harming healthy cells is not a trivial problem, and can often be assisted by the use of computational models of the patient. In this paper, a method for determining phased-array driving signals that result in a clinically favorable temperature distribution is presented. It is shown by example that simply focusing the power deposited over the tumor is not sufficient to guarantee that the peak temperature elevation occurs in the tumor in biological media. To remedy this, the temperature is predicted by a simple computational model and directly optimized as a function of the phased-array driving signals. To facilitate this optimization, superposition principles are used for both the electromagnetic and thermal models to minimize the number of computationally intensive forward problems that must be solved.

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Section: B Numerical Modeling and Optimizationmentioning

confidence: 99%

Section: B Three-dimensional Analysis Of a Phantommentioning

confidence: 99%

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Determination of electromagnetic phased-array driving signals for hyperthermia based on a steady-state temperature criterion

Kowalski

Jin

2000

IEEE Trans. Microwave Theory Techn.

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“…Plus, it has been shown that the FDTD method can improve the accuracy in modelling dielectric interfaces as well as the ability to assemble large tumours. So far, such a method has some success in solving bio-heat equations, which is applicable for simple cases of modelled objects or a simplified onedimensional solution [87]. Contrast to FDTD, authors in [88] developed numerical methods based on finite difference discretisation schemes for simulations and modelling of a 3D heat transfer problems in human bodies.…”

Section: Electromagnetic and Thermal Simulatorsmentioning

confidence: 99%

“…To solve equation 2.2, Finite-Different Time-Domain (FDTD) is used to calculate EM power depositions in human models [78,87]. The benefits of using this method are the ability to overcome modelling difficulties encountered from other methods, such as Method of Moment (MoM).…”

Section: Electromagnetic and Thermal Simulatorsmentioning

confidence: 99%

Focusing microwave hyperthermia in realistic environment for breast cancer treatment

Nguyen¹

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Microwave hyperthermia, a process that involves heating tumour cells, has been proposed as an alternative method of treating breast cancer. By sending microwave energy of a suitable frequency range to the breast, localised heating is induced by the applied electromagnetic radiation. It is important that the tumour is heated to a temperature greater than 42℃, (the required temperature for hyperthermia treatment) while keeping healthy tissue at normal body temperature. Several useful approaches have been proposed to direct microwave hyperthermia to cancerous tissue, including novel focusing methods and innovative microwave hardware designs. However, a number of challenges restricting the use of microwave systems in clinical medicine remain. Arguably, the most persisting engineering problem to overcome is achieving locally focused microwave power in the heterogeneous environment of the breast. In order to understand the challenges of microwave hyperthermia, considerably large computational efforts are required to solve 3D Electromagnetic (EM) problems in a complex model of breast tissue.The success of using microwave hyperthermia to treat breast cancer is highly dependent on the accuracy of the excitation signals utilised for each antenna element. Several research papers have reported various approaches on this topic. Although recent progress has been made in the investigation of microwave hyperthermia, the studies were mainly reliant upon oversimplified Radio Frequency (RF) models which assume point source applicators, and human breast phantoms which are mostly 2D models lacking tissue thermal-electric properties. As a result, it is infeasible to implement the proposed systems for clinical applications. This thesis aims to address the limitations of these earlier studies by modelling and constructing realistic human breast models and 3D antenna arrays. This will require the determination of correct phases and amplitudes for the excitation signals in a realistic environment by using a global optimisation method.The approaches proposed use actual antenna arrays to transmit microwave power while the excitation signals are optimised based on power distributions and thermal profiles induced in the patient-specific breast models. The first study based on 2D antenna arrays and patient-specific breast models is demonstrated in Chapter 3. In this study, microwave hyperthermia is performed in a realistic environment rather than over-simplified scenarios. In the recommended technique, electromagnetic focusing on patient-specific breast models concentrates the power at the tumour position while successfully keeping the power levels at other positions (healthy tissue) at minimum values. Several patient-specific breast models ranging from fatty tissue to highly dense tissue are used to investigate the effect of breast anatomy on the proposed focusing technique.ii Chapter 4 introduces an improved hyperthermia approach for breast cancer treatment, overcoming the limitations of previously analysed techniques. In this appro...

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Microwave scattering parameters of lossy materials: Experiments and computations

Lasri

Bocquet

Leroy

1996

Microw. Opt. Technol. Lett.

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lol I -loo 45 90 135 180 -6A 45 90 135 1:O Phi (degrees) Phi (degrees) 1 0 45 90 135 180 2 -30' 0 45 90 135 180 Phi (degrees) Phi (degrees) Figure 8 H-plane gain patterns for a 2 x 2 array of wire dipoles ohtained by superpoxition of the symmetric field patterns. Solid lines: ymmrtn-aided FDTD rewlts. Dottcd lines: method-of-rnoments results (NEC-2). ( a ) 0.5 GHz. ( h ) 1.0 GHz. (c) 1.5 GHz. ( d ) 2.0 GHzsingle-element field patterns. The results are nearly identical for the two calculations: the real and imaginary parts of the single-element E, in the far field agree to at least three decimal places a t all frequencics. The conventional FDTD code requires 28.3 megabytes of memory and 12.687 s of CPU time for a single run, whereas the symmetry-based code requires only 6.9 megabytes and 3,001 s of CPU time for a single run. These single-run results are summarized in Tablc 2. For either conventional or symmetry-aided FDTD. four runs arc required to calculate all four single-element field patterns. to which any desired set of amplitudes and phases can be applied. without the use of symmetry, 50,748 s of CPU are required for such a calculatiun, whereas only 12.004 seconds arc required when symmetry is used, yielding a memory and run-time savings of 3.1. IV. CONCLUSIONSThe computational resources-memory and CPU timerequired for FDTD simulations of finite phased arrays can be reduced if the array and its excitation possess one or more planes of symmetry. Each plane of symmetry can be replaced with a n electric or a magnetic wall. eliminating that part of the structure on the other side of the wall from consideration and reducing the meniory and run-time requirements by a factor of 2. For a planar array with two planes of symmetry, a factor of 4 reduction in the memory and run-time requirements is obtained. This technique can also be applied t o threc-dimensional arrays with one or more planes of symmetry. The FDTD analysis of a three-dimensional array having three planes of symmcty can be carried out with one-eighth TABLE 2 Performance Comparison Data for the FDTD ~ Number ot unknown\ 1,290,000 324,000 Mcmory required (MB) 28 4 6 9 CPU time per run (s) 12.687 3,001 the computational resources required for a conventional FDTD analysis. REFERENCES 1. ABSTRACT In order to deuelop new methods of nondestructive control of material by microwatws, we are te,yting ihe capabiliq of determining the transmission and reflection properties of a lossy material (i.e., the scattering parameters) in near-field situations. The results giuen by off-the-shelf sofnvare (Hewlett-Packard high fiequency structure simulator) are compared with other computed data obtained by a modal method and experimental daia @(,en by an automatic network analyzer. 0 1996 John Wiley & Sons, Inc.

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FDTD analysis of power deposition patterns of an array of interstitial antennas for use in microwave hyperthermia

Cited by 27 publications

References 20 publications

Determination of electromagnetic phased-array driving signals for hyperthermia based on a steady-state temperature criterion

Determination of electromagnetic phased-array driving signals for hyperthermia based on a steady-state temperature criterion

Focusing microwave hyperthermia in realistic environment for breast cancer treatment

Microwave scattering parameters of lossy materials: Experiments and computations

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