Optimization of the absorbed power distribution for an annular phased array hyperthermia system

Strohbehn, John W.; Curtis, Elizabeth H.; Paulsen, Keith D.; Yuan, Xingchao; Lynch, Daniel R.

doi:10.1016/0360-3016(89)90474-4

Cited by 45 publications

(11 citation statements)

References 24 publications

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“…As D(t k )approaches D f , to prevent the overshoot in the delivered thermal dose, the reference D ref (t)must become less aggressive so that the corresponding T 90,ref (t) is an attainable trajectory. One possible (φ,t) with the desired properties is given by the implicit parameterization (25) The slope α is calculated based on the difference between the delivered and the desired thermal dose, and the selected final treatment time (26) (27) where Δt is the tuning parameter, referred to as moving treatment horizon. The subsequent simulation results show the effect of Δt on the performance of K D .…”

Section: Feedback Control Of the Thermal Dosementioning

confidence: 99%

Minimum-Time Thermal Dose Control of Thermal Therapies

Arora

Skliar

Roemer

2005

IEEE Trans. Biomed. Eng.

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The problem of controlling noninvasive thermal therapies is formulated as the problem of directly controlling thermal dose of the target. To limit the damage to the surrounding normal tissue, the constraints on the peak allowable temperatures in the selected spacial locations are imposed. The developed controller has a cascade structure with a linear, constrained, model predictive temperature controller in the secondary loop. The temperature controller manipulates the intensity of the ultrasound transducer with saturation constraints, which noninvasively heats the spatially distributed target. The main nonlinear thermal dose controller dynamically generates the reference temperature trajectories for the temperature controller. The thermal dose controller is designed to force the treatment progression at either the actuation or temperature constraints, which is required to minimize the treatment time. The developed controller is applicable to high and low-intensity treatments, such as thermal ablation and thermoradiotherapy. The developed approach is tested using computer simulations for a one-dimensional model of a tumor with constraints on the maximum allowable temperature in the normal tissue and a constrained power output of the ultrasound transducer. The simulation results demonstrate that the proposed approach is effective at delivering the desired thermal dose in a near minimum time without violating constraints on the maximum allowable temperature in healthy tissue, despite significant plant-model mismatch introduced during numerical simulation. The results of in vitro and in vivo validation are reported elsewhere.

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Section: Feedback Control Of the Thermal Dosementioning

confidence: 99%

Minimum-Time Thermal Dose Control of Thermal Therapies

Arora

Skliar

Roemer

2005

IEEE Trans. Biomed. Eng.

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“…Electromagnetic transmitting arrays in the frequency band 60-2000 MHz are used to localize heating of malignant tumors within a target body. Many studies have been conducted to produce improved therapeutic field distributions with hyperthermia phased arrays [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32]. Phase control can be used to synthesize improved RF radiation patterns without adaptive control of the transmit-array weights (15)(16)(17)(18)(19)(20).…”

Section: Introductionmentioning

confidence: 99%

“…Phase control can be used to synthesize improved RF radiation patterns without adaptive control of the transmit-array weights (15)(16)(17)(18)(19)(20). Array transmit weights can be adaptively controlled to maximize the tumor temperature (or RF power delivered to the tumor) while minimizing the surrounding tissue temperature (or RF power delivered to the surrounding tissue) [21][22][23][24][25][26][27][28][29][30][31][32]. All other studies require invasive techniques to optimize the radiation pattern [21][22][23][24][25][26][27][28][29][30][31][32].…”

Section: Introductionmentioning

confidence: 99%

“…Array transmit weights can be adaptively controlled to maximize the tumor temperature (or RF power delivered to the tumor) while minimizing the surrounding tissue temperature (or RF power delivered to the surrounding tissue) [21][22][23][24][25][26][27][28][29][30][31][32]. All other studies require invasive techniques to optimize the radiation pattern [21][22][23][24][25][26][27][28][29][30][31][32]. A previous report [31 and several conference articles [4][5][6] investigate the theoretical benefit of using adaptive nulling with noninvasive auxiliary dipole sensors to reduce the field intensity at selected positions in the target body while maintaining a desired focus at a tumor.…”

Section: Introductionmentioning

confidence: 99%

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Adaptive radiofrequency hyperthermia-phased array system for improved cancer therapy: phantom target measurements

Fenn

King

1994

International Journal of Hyperthermia

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“…In Ref. [96] an attempt is made to minimise the integrated mean square error between the ideal SAR distribution and the calculated SAR delivered to the patient, assuming that the ideal distribution is unity in the tumour region and zero elsewhere. Another approach [16] consists in de®ning a speci®c performance indicator given as the ratio between deposited power in the tumour and the total power delivered both to the tumour and surrounding healthy tissues.…”

Section: Optimisation In Hyperthermic Treatmentmentioning

confidence: 99%

Operational research techniques in medical treatment and diagnosis: A review

Bartolozzi

Gaetano

Lena

et al. 2000

European Journal of Operational Research

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Many modern techniques for the diagnosis of pathological states in humans and for their subsequent treatment can be posed as nonlinear identi®cation problems of essentially nonlinear dynamic systems or as nonlinear optimal control problems. It can be shown that the linearised versions of such models are inadequate and do not represent at all well the complexity of the problem. Thus, nonlinear estimation and control techniques are required for progress to be made in this ®eld.The aim of this review is to examine some models suggested in the medical literature for the modelling of certain medical treatments and diagnoses. Then examine how these models can be enriched by using Operational Research techniques so that a better control is provided on the diagnosis and the treatment, as well as the formulation of more precise models of the phenomenon.The review will present some applications both therapeutic and diagnostic that have appeared in the literature. Special interest will be bestowed on hyperthermic systems in oncological treatment and glucose±insulin dynamics for diabetic patients, while heart dynamics and magnetic resonance imaging will also receive attention. These applications are good examples to show the advantages of Operational Research methods in this ®eld of endeavour.The outline of the paper is the following. After the introduction, in section two a brief description of nonlinear system models of phenomena will be given, for de®nitional and descriptive purposes. In section three a discussion of how to apply System theory in the medical ®eld will be presented, together with an analysis of the possible bene®ts. In section four some applications of dynamical models to medical diagnosis and treatment will be described, while in section ®ve the appropriate conclusions will be stated. Ó 2000 Published by Elsevier Science B.V. All rights reserved. 0377-2217/00/$ -see front matter Ó 2000 Published by Elsevier Science B.V. All rights reserved. PII: S 0 3 7 7 -2 2 1 7 ( 9 9 ) 0 0 0 1 7 -X

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Optimization of the absorbed power distribution for an annular phased array hyperthermia system

Cited by 45 publications

References 24 publications

Minimum-Time Thermal Dose Control of Thermal Therapies

Minimum-Time Thermal Dose Control of Thermal Therapies

Adaptive radiofrequency hyperthermia-phased array system for improved cancer therapy: phantom target measurements

Operational research techniques in medical treatment and diagnosis: A review

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