Quality assurance for radiofrequency regional hyperthermia

Hornsleth, S. N.; Frydendal, Lars; Mella, Olav; Dahl, Olav; Raskmark, Povl

doi:10.3109/02656739709012381

Cited by 23 publications

(21 citation statements)

References 13 publications

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“…In the present study we dedicated our attention to extending earlier work that has been done on step 2 [8]. Of course, it is difficult to separate waterbolus related influences from array related influences, especially at bolus-air transitions [15] [16]. However, waterbolus shapes are difficult to prescribe clinically and they highly depend on practical limitations.…”

Section: Discussionmentioning

confidence: 92%

A head and neck hyperthermia applicator: Theoretical antenna array design

Paulides

Bakker

Zwamborn

et al. 2007

International Journal of Hyperthermia

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Purpose: Investigation into the feasibility of a circular array of dipole antennas to deposit RF-energy centrally in the neck as a function of: 1) patient positioning, 2) antenna ring radius, 3) number of antenna rings, 4) number of antennas per ring and 5) distance between antenna rings. Materials and Methods: Power absorption (PA) distributions in realistic, head and neck, anatomy models are calculated at 433MHz. Relative PA distributions corresponding to different set-ups were analysed using the ratio of the average PA (aPA) in the target and neck region. Results: Enlarging the antenna ring radius from 12.5cm to 25cm resulted in a ∼ 21% decrease in aPA. By changing the orientation of the patients with respect to the array an increase by ∼ 11% was obtained. Increase of the amount of antenna rings led to a better focussing of the power (1 → 2 / 3 : ∼ 17%). Increase of the distance between the antenna rings resulted in a smaller (more target region conformal) focus but also a decreased power penetration. Conclusions: A single optimum array setup suitable for all patients is difficult to define. Based on the results and practical limitations a setup consisting of two rings of six antennas with a radius of 20cm and 6cm array spacing is considered a good choice providing the ability to heat the majority of patients.

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Section: Discussionmentioning

confidence: 92%

A head and neck hyperthermia applicator: Theoretical antenna array design

Paulides

Bakker

Zwamborn

et al. 2007

International Journal of Hyperthermia

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“…Gabriel et al 1996a, b, c) and a tissue type based patient description. This description can be extracted from diagnostic images by appropriate segmentation procedures (Sullivan 1990, Piket-May et al 1992, Hornsleth 1997, Wust et al 1998.…”

Section: Application Of the Weak Form Of The Cgfft Methods For The Amcmentioning

confidence: 99%

“…the Finite DiOE erence Time Domain method (FDTD, Sullivan 1990, Hornsleth 1992, 1997, the Finite Element (FE) method (Paulsen et al 1990, Jia et al 1994, the Volume Surface Integral Equation method (VSIE) (Nadobny et al 1992, Wust et al 1993, and the Weak Formulation of the Conjugate Gradient FFT method (CGFFT) (Zwamborn et al 1991(Zwamborn et al , 1992. The accuracy of the hyperthermia treatment simulation is of importance in treatment planning/thermal dosimetry for the individual patient and equipment development.…”

Section: Introductionmentioning

confidence: 99%

RF hyperthermia array modelling; validation by means of measured EM-field distributions

Wiersma

Dijk²

2001

Int. J. Hyperthermia

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The accuracy of a hyperthermia treatment simulation determines its role in prospective treatment planning and dosimetry for the individual patient. Of importance are (1) the accuracy of the numerical simulation method, and (2) the numerical description of the hyperthermia treatment system. The accuracy of the numerical method is generally determined by analysis of a problem that is analytically solvable. The validity of the description of the hyperthermia system is to be investigated by comparison of the simulated and measured EM-field amplitude and phase of the clinical operational hyperthermia system. In this paper, the numerical description of the AMC-4 waveguide phased array for which treatment planning is performed by the Weak Form of the Conjugate Gradient FFT method is investigated. The accuracy of the description is analysed for four set-ups, varying the bolus size and the number of waveguides attached to a phantom. The comparison of experimental and numerical data has demonstrated the ability of the Weak Formulation of the Conjugate Gradient FFT method to predict the EM-field of the AMC-4 waveguide array hyperthermia system, including effects due to bolus size variations. However, based on the comparison of the measured EM-field distributions and those obtained from simulations, the accuracy of the planning system is found to be insufficient for quantitative SAR dosimetry for individual patients. Qualitative SAR dosimetry can be applied in cases where the accuracy is of minor importance, e.g. for the retrospective analysis of problematic hyperthermia treatments. Prospective applications of the treatment planning system include the (qualitative) determination/simulation of a set of starting points giving a 'close to optimal' amplitude and phase setting, the prediction of possible problem areas and the analysis of the performance of new/improved hyperthermia devices.

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“…The neurological damage is probably determined by the sensitivity of the nerve vasculature which should be kept under a dose of 30 min at 44 C or equivalent. Hopefully, the introduction of specific absorption rate (SAR) based treatment planning and continuous non-invasive monitoring, will help in delivering homogenous heating and reduce thermal hot spots [193][194][195][196][197].…”

Section: Toxicity Issuesmentioning

confidence: 99%

Current status of antivascular therapy and targeted treatment in the clinic

Dahl

Borkamo

Fluge

2008

International Journal of Hyperthermia

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Antivascular and targeted therapy are now an integrated part of the treatment of myelogenous leukemias, GIST tumours, B-cell lymphomas and breast cancer. In various malignancies improved responses and prolongation of survival for several months is regularly reported. The progress in this field is relevant for hyperthermia. Heat has among other effects documented antivascular effects, and can be considered as one of the established methods in the field based on several randomised phase III studies. Hyperthermia should be considered for combination with other antiangiogenic agents.

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Quality assurance for radiofrequency regional hyperthermia

Cited by 23 publications

References 13 publications

A head and neck hyperthermia applicator: Theoretical antenna array design

A head and neck hyperthermia applicator: Theoretical antenna array design

RF hyperthermia array modelling; validation by means of measured EM-field distributions

Current status of antivascular therapy and targeted treatment in the clinic

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