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Hyperthermia treatment planning is a deeply patient-specific task which includes the optimal determination of the excitations of an array applicator. To enhance flexibility, various solutions exploiting different frequencies, antenna element, number, and applicator geometries have been proposed in the literature. Amongst them, increasing the frequency and the number of radiating elements have been effective for achieving more conformal heating. However, as each radiating element requires a power amplifier to control it, increasing the number of antennas considerably impacts the overall cost and complexity of the system. Accordingly, a procedure capable of selecting an optimal patient-specific subset of antennas from an oversized phased array applicator (with more antenna elements than available amplifiers) could help improve cost-effectiveness. In this study, we present an original approach, which allows improving performance by adaptively selecting the optimal subset of antennas to be activated for a given (redundant) applicator and a given patient. The proposed approach takes inspiration from the compressive sensing theory by embedding the sparsity promotion paradigm into a treatment planning procedure, which casts power deposition as a constrained convex optimization. Performances were demonstrated for the case of head and neck hyperthermia and benchmarked against the antenna selection procedure presently used in clinical practice.

We propose a new approach to the mask-constrained synthesis of shaped beams through generic array antennas having arbitrary layouts and element patterns. The introduced general methodology allows c...

Due to the plethora of possible applicative fallouts, in the recent years several efforts have been made to develop three-dimensional (3-D) field intensity shaping methods. While many approaches able to focus a wave-field into a target point are available, few strategies have been instead developed to generate a field having a given intensity spatial distribution. This is probably due to the higher challenging nature of such a problem. In this letter, with reference to scalar fields, we present an innovative 3-D shaping procedure, which casts the problem as the solution of a finite number of convex programming problems. An example of the performance of the proposed procedure in a 3-D inhomogeneous scenario is given to show the capability of ensuring uniform field intensity within a target area while keeping it arbitrarily bounded elsewhere.

Clinical effectiveness of hyperthermia treatments, in which tumor tissue is artificially heated to 40–44 °C for 60–90 min, can be hampered by a lack of accurate temperature monitoring. The need for noninvasive temperature monitoring in the head and neck region (H&amp, N) and the potential of MR thermometry prompt us to design an MR compatible hyperthermia applicator: the MRcollar. In this work, we validate the design, numerical model, and MR performance of the MRcollar. The MRcollar antennas have low reflection coefficients (&lt, −15 dB) and the intended low interaction between the individual antenna modules (&lt, −32 dB). A 10 °C increase in 3 min was reached in a muscle-equivalent phantom, such that the specifications from the European Society for Hyperthermic Oncology were easily reached. The MRcollar had a minimal effect on MR image quality and a five-fold improvement in SNR was achieved using the integrated coils of the MRcollar, compared to the body coil. The feasibility of using the MRcollar in an MR environment was shown by a synchronous heating experiment. The match between the predicted SAR and measured SAR using MR thermometry satisfied the gamma criteria [distance-to-agreement = 5 mm, dose-difference = 7%]. All experiments combined show that the MRcollar delivers on the needs for MR—hyperthermia in the H&amp, N and is ready for in vivo investigation.

In hyperthermia treatments, the possibility of generating a specific absorption rate distribution peaked into the tumor and bounded elsewhere represents the main clinical need. As multi-frequency applicators can be exploited to reduce the occurrence of undesired hot-spots, an optimal multi-frequency approach is proposed and discussed. Being formulated in terms of a convex programming problem, the globally optimal solution can be determined (only for very special cases). The procedure, presented for the case of scalar fields, can be extended both to the case of vector fields and to the more interesting problem of shaping (rather than just focusing) the specific absorption rate distribution.

Energy harvesting at radio frequencies (RF) is increasingly attracting interests because of the simplicity of its concept: collecting the RF energy through an antenna and a rectification circuit. This enables power-over-distance transmission, recharging of devices and communications and many other applications. However, the transferred power levels are inadequate due to uncertainties on the scenario and a non efficient confinement of the power transfer. In this work, the feasibility of a radically new approach based on RF field intensity focusing in unknown scenarios is discussed. The proposed approach is, in principle, able to maximize the energy transfer as it aims at confining the RF power on the considered RFID device. Moreover, being the approach based on a real-time procedure, it is able to deal with moving RFID tag embedded into an unknown scenario. Finally, the achieved spatial confinement will deliver private Peer to Peer communication.

Radiative (or far-field) energy replenishment for devices such as smartphones, laptops, robots, and small electric appliances paves the way to autonomous and continuous devices functioning, thus bypassing the need of operation interruptions, human maintenance activities, and replenishment by wired transformers. In this work, we investigate the feasibility of using a properly engineered antenna array able to deliver radiative power to devices in need of energy replenishment during their normal and unsupervised activity, whose locations are unknown. Both the case of single and multiple devices needing energy replenishment are addressed. A quantitative proof-of-concept study is carried out to validate the proposed approach. A 3D scenario is simulated to study the case of devices in need of energy replenishment within a standard office environment. Different antenna array configurations are investigated and the corresponding performances benchmarked against a standard installation of recharging antennas. Results confirm the outstanding capability of the proposed approach in terms of confinement and maximization of power transfer. Finally, in this framework, we also propose an efficient communication protocol that is able to manage multiple recharge demand given different operational rules.

Clinical trials have shown that hyperthermia is a potent adjuvant to conventional cancer treatments, but the temperatures currently achieved in the clinic are still suboptimal. Hyperthermia treatment planning simulations have potential to improve the heating profile of phased-array applicators. An important open challenge is the development of an effective optimization procedure that enables uniform heating of the target region while keeping temperature below a threshold in healthy tissues. In this work, we analyzed the effectiveness and efficiency of a recently proposed optimization approach, i.e. focusing via constrained power optimization (FOCO), using 3D simulations of twelve clinical patient specific models. FOCO performance was compared against a clinically used particle swarm based optimization approach. Evaluation metrics were target coverage at the 25% iso-SAR level, target hotspot quotient, median target temperature (T50) and computational requirements. Our results show that, on average, constrained power focusing performs slightly better than the clinical benchmark ([Formula: see text]T50 [Formula: see text] °C), but outperforms this clinical benchmark for large target volumes ([Formula: see text]40 cm[Formula: see text], [Formula: see text]T50 [Formula: see text] °C). In addition, the results are achieved in a shorter time ([Formula: see text]%) and are repeatable because the approach is formulated as a convex optimization problem.

In this contribution, an original approach for invivo estimation of electrical properties of biological tissues is presented. Such an estimation represents an essential step in hyperthermia treatment planning, wherein typically magnetic resonance or computerized tomography images are exploited and turned into electric parameters, based on available ex-vivo measured properties, to predict the effects of the treatment. As parameters change from patient to patient and can be quite different from the ex-vivo ones, the proposed approach is based on the solution of an inverse scattering problem, processing backscattered data measured from the patient and conveniently exploiting the morphological information on tissues available from medical images, to overcome the well-known issues arising in the solution of inverse problems.

Clinical studies have shown the benefit of hyperthermia as a strong adjuvant to conventional cancer treatments but a tight control of the administered heating still represents an open challenge. Planning the hyperthermia treatment is the way to deliver a target conformal specific absorption rate (SAR) deposition over the target area while keeping the SAR bounded in normal tissue. This task is even more challenging in case of large and irregularly shaped target volumes. Motivated by this need, the so-called multi-target focusing via constrained power optimization was developed. In the current study, we investigated the effective gain in terms of heating profile of the proposed approach using simulations of 3D clinical patient specific models. Results indicate an average median temperature gain of 0.8°C with respect to standard FOCO.

We propose a new approach to the mask-constrained synthesis of shaped beams through fixed-geometry array antennas. The problem is cast as a (limited) number of convex programming optimizations and can deal with all kinds of linear and planar arrays, including non-uniformly spaced arrays.

This contribution introduces a novel approach for in-vivo estimation of electrical properties of biological tissues based on the solution of an inverse scattering problem and on an innovative use of morphological maps derived by magnetic resonance imaging or other medical imaging techniques. This issue is relevant in different medical applications, especially in hyperthermia treatment planning, where the expected performances are evaluated on the basis of the adopted electrical model of the patients. A preliminary numerical example of the proposed mapping is given dealing with a realistic head model.

The estimation of conductivity and permittivity of biological tissues is fundamental in the determination of the specific absorption rate (SAR) and electromagnetic field intensity distribution in hyperthermia treatment planning. In this contribution, an original approach for the in-vivo estimation of these parameters is introduced. The proposed approach is based on the solution of an inverse scattering problem and the innovative use of the morphological map of biological tissue exacting by medical images, obtained by means of magnetic resonance imaging or computed tomography.

This communication describes the ongoing efforts towards the assessment of microwave imaging as a tool for real-time monitoring of thermal ablation treatments. In particular, the ex-vivo experimental set-up adopted for the validation is described, and the results of a preliminary experiment are shown. Notably, by analyzing pre- and post-ablation treatment data it is possible to recognize the footprint of the interface between the ablated and not-ablated tissue, making it possible to estimate the boundary of the treated area.

The enhancing effect of hyperthermia when combined to radio- and chemio-therapy allow a relevant improvement of such anti-cancer treatments. This communication presents an innovative hyperthermia treatment planning strategy that selectively focus/shape the specific absorption rate deposition within the tumor, while avoiding the unde-sired heating of healthy tissues. This latter represents one of the main therapeutical challenges. Because of its formulation (as a convex programming problem) and the use of multi-frequency applicator, the proposed approach is able to both deliver the global optimal solution of the problem and gather a better control of hot-spots occurrence. The approach is presented for the case of scalar fields, but it is conceptually extendable to vector fields as well.

This paper presents the results of a broadband microwave spectroscopy of a diluted water-based ferrofluid, when subject to an external polarizing magnetic field (PMF) of variable intensity. The characterization has been performed exploiting a recently proposed measurement approach, specifically devised to enable accurate measurement of the magnetic properties of such suspensions, properly modified to consider the presence of an applied PMF. To investigate in detail the nature of the response and of its dependence on the applied PMF, the measured susceptibilities have been fitted with a superposition of relaxation and resonance dispersion models. Besides quantitatively assessing results already reported in the literature for similar magnetic nanoparticles (MNPs), but suspended in hydrocarbons the analysis has also led to an unexpected result, namely, the onset of a second ferromagnetic resonance when the PMF exceeds 20 kA/m. Apart from their physical interest, the obtained results provide an accurate and comprehensive characterization of the magnetic response of a class of MNPs exploitable in all the emerging biomedical applications based on the interaction of MNPs and electromagnetic fields, such as microwave imaging.