1,721,027 research outputs found
Hyperthermia phased arrays pre-treatment evaluation
No full textPurpose: In the hyperthermia treatment of deep-seated tumours by a phased array of radiofrequency
(RF) antennas, heatability will be investigated in terms of power-to-tumour and other figures-of-merit
of hyperthermia treatments to be optimised. The assumption is that each source is individually constrained
to not exceed a maximal nominal power. The nominal power may differ from a source to
another as a physical limit or an operative modality.
Method: Under such constraint, new procedures for the maximisation of (i) power-to-tumour, (ii) heating
efficiency and, in general, (iii) power ratios as tumour-heating selectivity are proposed. (iv) The
problem whether a tumour is equally heatable after turning off some antennas is addressed as array
thinning.
Case study: An array of eight dipoles arranged on two lines around a head/neck is introduced to perform
a numerical analysis. The achievable power-to-tumour according to the new optimizations and
other performance indices adopted from the literature is tested against values of power that can be
found to be sufficient for heating tumours to clinical temperatures. New solutions to data rendering in
hyperthermia heating are proposed
Analysis of the EMI Impact of an Array of Wind Generators on the Performances of Secondary Surveillance Radar System
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Figures of merit and their bounds in radiofrequency heating by phased arrays
No full textPurpose: The problem of effective power delivery to a semi-deep target by a phased array has
been addressed for application to hyperthermia treatment of some tumours in the thorax.
Methods: Three efficiencies have been introduced, which estimate system ability in power
transfer from generators to body, from body to tumour, and from generators to tumour. They
are formulated in terms of a dissipation matrix and an interference matrix. Bounds to achievable
efficiencies are obtained. Further figures of merit have also been introduced. The necessary
mathematics has been developed.
Results: A numerical analysis has been carried out for a partially interdigitated planar array of
resonant dipoles. Results show how the new parameters can be exploited for optimal selection
of the array’s degrees of freedom.
Conclusion: The figures of merit and their bounds allow comparisons between RF heating
devices and provide guidelines to phased array design
Phased Arrays Pre-treatment Evaluation in Antitumoral Hyperthermia
No full textThere is general consensus that quality of hyperthermia treatment is a key factor
for clinical effectiveness. The optimal treatment is defined by efficient tumor heating without
patient discomfort by hot spots. Two optimization methods with the constraint on amplifier
nominal power are presented. A voxel-based numerical analysis is performed for 8 dipoles on two
rings, positioned around a head/neck volume within a distilled-water bolus. The optimization
methods are compared on the basis of the maximal absolute power delivered to the target and
other previously defined parameter
New method for modelling and design of multiconductor airborne antennas
No full textA new approach is proposed, based on numerical (FDTD) and analytical (multi-
conductor transmission line MTL) tools, for the modelling of HF loop antennas mounted on
aircraft. This method can be used to calculate the significant mutual coupling and the interaction
with the body of the aircraft and also to perform fast optimisation of antenna size and position
A Voxel-Based Approach in Phased-Array Optimization for Microwave Hyperthermia
No full textThe problem of effective power delivery to a deep
target by a near-field phased array has been addressed for
application to oncological hyperthermia. Phased arrays are
evaluated on the basis of their ability to deliver the largest
fraction of the available power from generators to a tumor. Each
voxel of the heated volume was considered as a target, a tumor
being the union of some such voxels. Maps of efficiencies and an
array factor have been produced for a head-neck volume. These
maps may help in appreciating tumor heatability by the phased
array
Exploring 434 MHz phased array for hyperthermia heating of semi-deep targets
No full textThe problem of effective power delivery to a semi-deep tumor by a near-field phased array is addressed with reference to hyperthermia treatments. Phased array are evaluated on the basis of their ability to deliver the largest fraction of the available power from the generators to a target. With this aim, some efficiencies and an array factor are estimated for each cell of the body segment, when that cell is considered as target. The results are presented as color maps of heating efficiency and array factor. A model of tumor is the union of some of these cells. The maps may help in appreciating its heatability by the phased array. Different arrays can thus be numerically experimented to select the one which delivers most power to the tumor. Field polarization is taken into account and loss of efficiency related to polarization mismatch is considered, too. As an example, an array of 8 antennas, operating at 434 MHz, is positioned around a numerical modelling of a human head. The following figures show, for this example,: a) the Array Factor (each pixel of this image shows the Array Factor when the same pixel is the target of the optimization process); b) the polarization status for the Electric field inside the head, when one of the antennas is energized
Modello circuitale a linea di trasmissione per la risoluzione dell’equazione del calore, in strutture stratificate, con condizioni al contorno non-lineari ed eccitazione periodica: un’applicazione al caso della crosta lunare
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