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The aim of the article is to provide a summary of the work carried out in the framework of a research project funded by the Italian Ministry of Research. The main goal of the activity was to introduce multiple tools for reliable, affordable, and high-performance microwave hyperthermia for cancer therapy. The proposed methodologies and approaches target microwave diagnostics, accurate in vivo electromagnetic parameters estimation, and improvement in treatment planning using a single device. This article provides an overview of the proposed and tested techniques and shows their complementarity and interconnection. To highlight the approach, we also present a novel combination of specific absorption rate optimization via convex programming with a temperature-based refinement method implemented to mitigate the effect of thermal boundary conditions on the final temperature map. To this purpose, numerical tests were carried out for both simple and anatomically detailed 3D scenarios for the head and neck region. These preliminary results show the potential of the combined technique and improvements in the temperature coverage of the tumor target with respect to the case wherein no refinement is adopted.

BACKGROUND: The success of cancer hyperthermia (HT) treatments is strongly dependent on the temperatures achieved in the tumor and healthy tissues as it correlates with treatment efficacy and safety, respectively. Hyperthermia treatment planning (HTP) simulations have become pivotal for treatment optimization due to the possibility for pretreatment planning, optimization and decision making, as well as real-time treatment guidance.MATERIALS AND METHODS: The same computational methods deployed in HTP are also used for in silico studies. These are of great relevance for the development of new HT devices and treatment approaches. To aid this work, 3 D patient models have been recently developed and made available for the HT community. Unfortunately, there is no consensus regarding tissue properties, simulation settings, and benchmark applicators, which significantly influence the clinical relevance of computational outcomes.RESULTS AND DISCUSSION: Herein, we propose a comprehensive set of applicator benchmarks, efficacy and safety optimization algorithms, simulation settings and clinical parameters, to establish benchmarks for method comparison and code verification, to provide guidance, and in view of the 2021 ESHO Grand Challenge (Details on the ESHO grand challenge on HTP will be provided at https://www.esho.info/).CONCLUSION: We aim to establish guidelines to promote standardization within the hyperthermia community such that novel approaches can quickly prove their benefit as quickly as possible in clinically relevant simulation scenarios. This paper is primarily focused on radiofrequency and microwave hyperthermia but, since 3 D simulation studies on heating with ultrasound are now a reality, guidance as well as a benchmark for ultrasound-based hyperthermia are also included.

Temperature monitoring plays a central role in improving clinical effectiveness of adjuvant hyperthermia. The potential of magnetic resonance thermometry for treatment monitoring purposes led to several MR-guided hyperthermia approaches. However, the proposed solutions were sub-optimal due to technological and intrinsic limitations. These hamper achieving target conformal heating possibilities (applicator limitations) and accurate thermometry (inadequate signal-to-noise-ratio (SNR)). In this work, we studied proof of principle of a dual-function hyperthermia approach based on a coil array (64 MHz, 1.5 T) that is integrated in-between a phased array for heating (434 MHz) for maximum signal receive in order to improve thermometry accuracy. Hereto, we designed and fabricated a superficial hyperthermia mimicking planar array setup to study the most challenging interactions of generic phased-array setups in order to validate the integrated approach. Experiments demonstrated that the setup complies with the superficial hyperthermia guidelines for heating and is able to improve SNR at 2-4 cm depth by 17%, as compared to imaging using the body coil. Hence, the results showed the feasibility of our dual-function MR-guided hyperthermia approach as basis for the development of application specific setups.

Purpose: To develop a head and neck hyperthermia phased array system compatible with a 1.5 T magnetic resonance (MR) scanner for noninvasive thermometry. Methods: We designed a dielectric-parabolic-reflector antenna (DiPRA) based on a printed reflector backed dipole antenna and studied its predicted and measured performance in a flat configuration (30 mm thick water bolus and muscle equivalent layer). Thereafter, we designed a phased array applicator model (‘MRcollar’) consisting of 12 DiPRA modules placed on a radius of 180 mm. Theoretical heating performance of the MRcollar model was benchmarked against the current clinical applicator (HYPERcollar3D) using specific (3D) head and neck models of 28 treated patients. Lastly, we assessed the influence of the DiPRA modules on MR scanning quality. Results: The predicted and measured reflection coefficients (S 11) of the DiPRA module are below −20 dB. The maximum specific absorption rate (SAR) in the area under the antenna was 47% higher than for the antenna without encasing. Compared to the HYPERcollar3D, the MRcollar design incorporates 31% less demineralized water (−2.5 L), improves the predicted TC25 (target volume enclosed by 25% iso-SAR contour) by 4.1% and TC50 by 8.5%, while the target-to-hotspot quotient (THQ) is minimally affected (−1.6%). MR experiments showed that the DiPRA modules do not affect MR transmit/receive performance. Conclusion: Our results suggest that head and neck hyperthermia delivery quality with the MRcollar can be maintained, while facilitating simultaneous noninvasive MR thermometry for treatment monitoring and control.

Purpose: Thermal dose-effect relations have demonstrated that clinical effectiveness of hyperthermia would benefit from more controlled heating of the tumor. Hyperthermia treatment planning (HTP) is a potent tool to study strategies enabling target conformal heating, but its accuracy is affected by patient modeling approximations. Homogeneous phantoms models are being used that do not match the body shape of patients in treatment position and often have unrealistic target volumes. As a consequence, simulation accuracy is affected, and performance comparisons are difficult. The aim of this study is to provide the first step toward standardization of HTP simulation studies in terms of patient modeling by introducing the Erasmus Virtual Patient Repository (EVPR): a virtual patient model database.Methods: Four patients with a tumor in the head and neck or the pelvis region were selected, and corresponding models were created using a clinical segmentation procedure. Using the Erasmus University Medical Center standard procedure, HTP was applied to these models and compared to HTP for commonly used surrogate models.Results: Although this study was aimed at presenting the EVPR database, our study illustrates that there is a non-negligible difference in the predicted SAR patterns between patient models and homogeneous phantom-based surrogate models. We further demonstrate the difference between actual and simplified target volumes being used today.Conclusion: Our study describes the EVPR for the research community as a first step toward standardization of hyperthermia simulation studies.

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...

Temperature monitoring is essential for a controlled application of hyperthermia in the head & neck to counteract the heterogeneous thermoregulation. Magnetic resonance (MR) thermometry can be used to monitor the 3D temperature pattern, so we are developing the world’s first hyperthermia applicator for MR guided treatment of head & neck cancers. To maximize imaging signal-to-noise (SNR) but also allow an independent choice of the radiofrequencies for imaging and heating, our approach is based on integrating heating antenna- and imaging coil-arrays into one device. In this work, we developed and experimentally assessed the dual-function using a 3channel receiver-only coil array designed for a 1.5T MR scanner (64 MHz) integrated into one of the two MRcollar shells containing six antennas operating at 434 MHz. Vector network analyzer measurements showed an average S ii equal to -14dB and S ij equal to -12dB with a 2cm geometric overlap. MR imaging experiments showed an average SNR improvement of +40 dB when comparing the proposed coil to the conventional body coil. Results show the feasibility of the approach, and therefore paves the way for a clinical prototype for testing our dual-function approach in phantoms, volunteers and patients.

Field intensity shaping is a challenging open problem of interest for many applications. The several approaches proposed are based on a complete knowledge of both the scenario and the target. This, instead, is not necessarily possible. The aim of this communication is to propose a novel adaptive procedure able to shape the field intensity in an unknown (or partially unknown) scenario. The approach originates from the physical interpretation of the Linear Sampling Method and takes advantage from using both control points and an additional degree of freedom represented by phase shifts of the field at these control points.

MR compatible hyperthermia devices exploit MR thermometry capabilities for non-invasive treatment monitoring. These devices, which have been tested to be MR-safe, can potentially influence the MR image quality. One such device is the Pyrexar BSD-2000 3D/MR applicator. In this study, we quantitatively evaluated the impact of the applicator for different setups on MR imaging by B1 + and signal-to-noise (SNR) measurements. Our results show 30% decrease in the B1 + transmit efficiency and 20% decrease in the SNR. We have found the biggest impact was caused by the device's water bolus. This effect can be overcome by increasing the B1 transmit gain or using a thinner water bolus in the device design.

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.

An experimental study is carried out to assess the effect of temperature on the conversion efficiency of ultrahigh-frequency energy harvesters based on diode-capacitor Dickson charge pumps, frequently used in self-energizing circuits, such as in radio frequency identification tags or in wireless sensor nodes. Using off-the-shelf Schottky diodes often adopted for this application, it is shown that the harvester conversion efficiency at 868 MHz is temperature dependent due to the changing rectification ratio, namely the ratio between the forward and the reverse current flowing through the low barrier height Schottky diodes, which both show a positive derivative with T. The experimental study, supported by SPICE simulations, has shown that a temperature variation might be particularly harmful at the lowest incident power regimes, when even a minimal drop in the conversion efficiency might determine the out-of-servicing of a wirelessly energized circuit.

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.

Clinical effectiveness of hyperthermia would benefit from a more controlled and target conformal heating of the tumor. Over the years, dosimetry using electromagnetic simulators has become a potent tool to study improvements in the application of hyperthermia. Literature suggests that simulation accuracy is dependent on the realism of the patient models. In this work, we compare the results for a detailed head and neck patient model to those for models with an approximated shape, a reduced tissue number and/or a spherical target volume. Our comparison shows a relative difference above 25% in the administered power absorption pattern. This large difference calls upon 1) follow-up research to establish the true impact using a larger set of patient models and 2) the development of a reference set of patient models to facilitate benchmarking of novel devices, methods and treatment approaches.

The potential of MR thermometry (MRT) fostered the development of MRI compatible radiofrequency (RF) hyperthermia devices. Such device integration creates major technological challenges and a crucial point for image quality is the water bolus (WB). The WB is located between the patient body and external sources to both couple electromagnetic energy and to cool the patient skin. However, the WB causes MRT errors and unnecessarily large field of view. In this work, we studied making the WB MRI transparent by an optimal concentration of compounds capable of modifying T 2 * relaxation without an impact on the efficiency of RF heating. Three different T 2 * reducing compounds were investigated, namely CuSO 4 , MnCl 2 , and Fe 3 O 4 . First, electromagnetic properties and T 2 * relaxation rates at 1.5 T were measured. Next, through multi-physics simulations, the predicted effect on the RF-power deposition pattern was evaluated and MRT precision was experimentally assessed. Our results identified 5 mM Fe 3 O 4 solution as optimal since it does not alter the RF-power level needed and improved MRT precision from 0.39 ∘ C to 0.09 ∘ C. MnCl 2 showed a similar MRT improvement, but caused unacceptable RF-power losses. We conclude that adding Fe 3 O 4 has significant potential to improve RF hyperthermia treatment monitoring under MR guidance.

Arbitrary shaping the field intensity is a challenging problem relevant in many applications. To date, procedures addressing such a challenging problem have been developed assuming a full knowledge of both the scenario and the target within embedded. However, this is not the case in many applications where the investigated scenario is only approximately known and/or modeled on the basis of some auxiliary imaging methods. In this article, we propose a novel adaptive procedure able to shape the field intensity in an unknown (or partially unknown) scenario without the need of a quantitative scenario retrieval. The approach takes advantage from the linear sampling method, which belongs to the class of qualitative imaging methods, in order to focus the field intensity with respect to different control points belonging to the target. Then, the desired spatial field intensity shaping is obtained by recombining the results from such single-focusing problems and by exploiting an additional degree of freedom, which is represented by phase shifts of the field in the considered control points. A preliminary numerical validation and assessment are given for in-homogeneous and lossy unknown 2-D scenarios.

Clinical outcome of hyperthermia depends on the achieved target temperature, therefore target conformal heating is essential. Currently, invasive temperature probe measurements are the gold standard for temperature monitoring, however, they only provide limited sparse data. In contrast, magnetic resonance thermometry (MRT) provides unique capabilities to non-invasively measure the 3D-temperature. This study investigates MRT accuracy for MR-hyperthermia hybrid systems located at five European institutions while heating a centric or eccentric target in anthropomorphic phantoms with pelvic and spine structures. Scatter plots, root mean square error (RMSE) and Bland&ndash, Altman analysis were used to quantify accuracy of MRT compared to high resistance thermistor probe measurements. For all institutions, a linear relation between MRT and thermistor probes measurements was found with R2 (mean &plusmn, standard deviation) of 0.97 &plusmn, 0.03 and 0.97 &plusmn, 0.02, respectively for centric and eccentric heating targets. The RMSE was found to be 0.52 &plusmn, 0.31 &deg, C and 0.30 &plusmn, 0.20 &deg, C, respectively. The Bland-Altman evaluation showed a mean difference of 0.46 &plusmn, C and 0.13 &plusmn, 0.08 &deg, C, respectively. This first multi-institutional evaluation of MR-hyperthermia hybrid systems indicates comparable device performance and good agreement between MRT and thermistor probes measurements. This forms the basis to standardize treatments in multi-institution studies of MR-guided hyperthermia and to elucidate thermal dose-effect relations.

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.

The estimation of electrical properties of living biological tissues is relevant to several medical applications ranging from hyperthermia treatment planning to dosimetry and, more in general, is pivotal for a fundamental understanding of bioclectromagnetic interactions. Non-invasive electromagnetic imaging, either based on the processing of electric fields measured via microwave tomography or magnetic fields acquired in magnetic resonance is suitable to pursue this goal. In this framework, the possibility of imaging without the need of phase information would be extremely relevant, as it would enable simpler and more reliable devices and would avoid limiting assumptions typically used in the literature. With reference to the canonical yet significant 2D case, in this paper we propose an inverse scattering approach for tissue characterization from only-amplitude electromagnetic data, which, by virtue of a unified mathematical framework, is viable for both microwave tomography and magnetic resonance imaging. The key feature of the method is the innovative use of morphological maps derived by other medical imaging modalities as prior spatial information, In particular, these images arc exploited to define a convenient and effective patient-specific representation of the unknowns. The approach is tested against simulated data derived from anatomically realistic scenarios.

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.

Since the cost of hyperthermia equipment is largely dependent on the number of amplifiers, new applicators are being developed that allow to exploit during treatment only a subset of antennas among those constituting the device. The selection of the optimal subset is a part of the treatment planning procedure and requires proper approaches to be carried out. In this contribution, we propose and test a new procedure that pursues the selection goal by embedding the sparsity promotion paradigm within an optimal treatment planning approach based on constrained power optimization. Thanks to such an integration, the proposed approach enables the simultaneous selection of the optimum antennas subset and the determination of their excitation feeding for maximizing target SAR while constraining the SAR elsewhere.

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.

Generating given 3-D field intensity distributions in a non-homogeneous scenario is a canonical problem which is of interest in many applications. On the other side, due to its very challenging nature, very few methods have been proposed up to now in the literature. In this communication, starting from the well-known time reversal (TR) technique, a simple innovative approach, the so-called optimized multi-target TR (O-mt-TR), is presented. The strategy is based on the optimization of the phase shifts between the time-reversed fields in a number of control points within the target region. In doing so, the proposed method outperforms the simple juxtaposition of time-reversed fields pursued by the so-called mt-TR, or even succeed in cases in which the latter fails completely. This capability of the proposed method is assessed through a numerical analysis concerned with a 3-D inhomogeneous scenario, in which the results are quantitatively appraised in terms of coverage of the target areas.

The possibility of uniformly shaping the SAR deposition over a target area while avoiding normal tissue to be undesirably heated represents one of the main open challenges in hyperthermia treatment planning. This task is even more challenging when dealing with large targets generally characterized by irregular shapes. Two innovative SAR shaping strategies, aimed at addressing the above-mentioned need, have been recently proposed. These strategies take advantage from the use of more target points and are respectively based on two well-known focusing techniques. In this communication, both the approaches are firstly given under a common mathematical framework and then tested on anatomically and electromagnetically realistic phantoms.

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.

One of the main open challenges in hyperthermia treatment planning is the possibility of uniformly shaping the SAR deposition over a target area, while keeping it bounded in normal tissue. This task is even more challenging as dielectric tissues parameters are prone to uncertainties and targets can be large and irregularly shaped. In this respect, an innovative SAR shaping strategy aimed at addressing the above-mentioned needs, the so-called multi-target focusing via constrained power optimization, has been proposed. This approach has been tested using 3D clinical patient models, exploiting Sim4Life as a simulation platform, and the results show the gain attainable by exploiting the proposed strategy and its robustness in the presence of electromagnetic tissue parameter uncertainties.

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.

In this communication, we present a full-wave numerical study aimed at showing the potential of microwave tomography as a tool to monitor microwave ablation of solid tumors. The goal is to track the changes in dielectric properties of the tissue undergoing the treatment, in order to appraise the evolving dimension and shape of the thermally ablated area surrounding the applicator. Such an in-line monitoring capability would entail a significant improvement in the therapeutic effectiveness of cancer treatments exploiting microwave ablation, both in terms of optimization/personalization of the therapeutic protocol and of reduction of unwanted side effects due to the unwanted increase of temperature in healthy tissues. The numerical study involves a scenario inspired by an existing experimental set-up, already used for the ex-vivo assessment of microwave ablation treatments. Hence, the promising results we have obtained, fully motivate us to progress towards the experimental demonstration of the concept in ex-vivo conditions. © 2017 Euraap.

Generating a given field intensity distribution in a non homogeneous scenario is a problem of interest in many applications. Due to the challenging nature of the problem, very few approaches have been presented so far, and none of them has fully addressed all the pertaining issues yet. In this communication we present an innovative and relatively simple shaping approach that relies on an optimized version of the well know time reversal method, named Optimized multi target Time Reversal. To appraise the performances of the proposed approach, a numerical assessment and a comparison with a recent and related shaping procedure available in the literature is reported.

Microwave thermal ablation is a cancer treatment that exploits local heating caused by a microwave electromagnetic field to induce coagulative necrosis of tumor cells. Recently, such a technique has significantly progressed in the clinical practice. However, its effectiveness would dramatically improve if paired with a noninvasive system for the real-time monitoring of the evolving dimension and shape of the thermally ablated area. In this respect, microwave imaging can be a potential candidate to monitor the overall treatment evolution in a noninvasive way, as it takes direct advantage from the dependence of the electromagnetic properties of biological tissues from temperature. This paper explores such a possibility by presenting a proof of concept validation based on accurate simulated imaging experiments, run with respect to a scenario that mimics an ex vivo experimental setup. In particular, two model-based inversion algorithms are exploited to tackle the imaging task. These methods provide independent results in real-time and their integration improves the quality of the overall tracking of the variations occurring in the target and surrounding regions.

In the framework of medical applications of microwaves, magnetic nanoparticles enhanced microwave imaging represents a promising diagnostic modality. As a matter of fact, it merges the safety, low-cost and portability of microwave technology with the increased specificity enabled by the selective targeting capability of magnetic nanoparticles. In particular, a key ingredient of this technique is the possibility of modulating the response of nanoparticles in the microwave range by means of an external polarizing magnetic field. To this end, the amplitudes of the polarizing field have to be properly set, in order to achieve optimal performances. In this communication, we present an experimental study aimed at optimizing the working conditions in terms of field strength of a ultra-wide band radar system for detecting a magnetic nanoparticle induced contrast.

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.