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Magnetic nanoparticles enhanced microwave imaging relies on the capability of modulating the response of such nanocomponents at microwaves by means of a (low frequency) polarizing magnetic field. In medical imaging, this capability allows for the detection and imaging of tumors loaded with nanoparticles. As the useful signal is the one which arises from nanoparticles, it is crucial to remove sources of undesired disturbance to enable the diagnosis of early-stage tumors. In particular, spurious signals arise from instrumental drift, as well as from the unavoidable interaction between the polarizing field and the imaging system. In this paper, we experimentally assess and characterize such spurious effects in order to set the optimal working conditions for magnetic nanoparticles enhanced microwave imaging of cancer. To this end, simple test devices, which include all components typically comprised in a microwave imaging system, have been realized and exploited. The experiment’s results allow us to derive design formulas and guidelines useful for limiting the impact of unwanted magnetic effects, as well as that relative to the instrumental drift on the signal generated by the magnetic nanoparticles-loaded tumor.

Magnetic nanoparticles-aided microwave imaging is an emerging modality for the diagnosis of early stage tumors. It exploits the possibility of modulating the response at microwaves of magnetic nanoparticles, employed as contrast agent selectively accumulated into the tumor. In this paper, we describe the results of an experimental study aimed at establishing the actual detection limits of the approach, namely the minimum amount of magnetic nanoparticles to be delivered for a reliable imaging. The assessment is carried out on breast phantoms made of ex-vivo minced pig tissues and using commercially available magnetic nanoparticles. The results show that it is possible to detect amounts of magnetic nanoparticles between 2 and 7 mg, dispersed in a volume of about one cubic centimeter, depending on the breast type. While such quantities are already consistent with those currently reachable via active selective targeting, an in-depth analysis of the results allows to identify strategies to further lower the detection limits up to four times, by refining the measurement set-up and setting the amplitude of the polarizing magnetic field modulating the nanoparticle response to a suitable value.

This paper presents a novel approach to microwave hyperthermia exploiting magnetic nanoparticles as focusing agents, and reports the results of a 2D numerical study aimed at preliminarily assessing its effectiveness. The approach exploits magnetic nanoparticles, locally supplied to the tumor, to induce, through an external polarizing magnetic field, a detectable variation of its magnetic contrast. This variation is exploited to determine the excitations of the antenna array focusing the electromagnetic energy on the tumor. The advantage is that the synthesis of the excitations does not require any information neither on the geometry nor on the electromagnetic properties of the treated region, thus achieving totally blind field focusing. The magnetic nature of the magnetic nanoparticles contrast has required the development of an ad-hoc synthesis strategy, which, together with the use of magnetic nanoparticles, represents the novelty of the approach.

Magnetic nanoparticles (MNP) enhanced microwave imaging has been recently proposed as a tool to pursue the diagnostics of breast cancer in an effective and reliable way. By means of a numerical analysis carried out under realistic conditions, this letter aims at assessing the measurement dynamic range (i.e., the measurement resolution), in terms of tumor size, nanoparticles concentration, and working frequency, required for an apparatus based on this diagnostic approach.

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.

Purpose: This paper presents a numerical study aiming at assessing the effectiveness of a recently proposed optimisation criterion for determining the optimal operative conditions in magnetic nanoparticle hyperthermia applied to the clinically relevant case of brain tumours. Materials and methods: The study is carried out using the Zubal numerical phantom, and performing electromagnetic–thermal co-simulations. The Pennes model is used for thermal balance; the dissipation models for the magnetic nanoparticles are those available in the literature. The results concerning the optimal therapeutic concentration of nanoparticles, obtained through the analysis, are validated using experimental data on the specific absorption rate of iron oxide nanoparticles, available in the literature. Results: The numerical estimates obtained by applying the criterion to the treatment of brain tumours shows that the acceptable values for the product between the magnetic field amplitude and frequency may be two to four times larger than the safety threshold of 4.85 × 108A/m/s usually considered. This would allow the reduction of the dosage of nanoparticles required for an effective treatment. In particular, depending on the tumour depth, concentrations of nanoparticles smaller than 10 mg/mL of tumour may be sufficient for heating tumours smaller than 10 mm above 42 °C. Moreover, the study of the clinical scalability shows that, whatever the tumour position, lesions larger than 15 mm may be successfully treated with concentrations lower than 10 mg/mL. The criterion also allows the prediction of the temperature rise in healthy tissue, thus assuring safe treatment. Conclusions: The criterion can represent a helpful tool for planning and optimising an effective hyperthermia treatment.

Magnetic nanoparticle enhanced microwave imaging has been recently proposed as an effective strategy to monitor breast cancer. In this communication, we describe the ongoing activities concerned with a first experimental feasibility assessment of this technique. Such an activity aims at providing a proof-of-concept in realistic working conditions and it is obviously necessary to proceed towards the stage of pre-clinical trials.

This communication deals with a recently proposed methodology for breast cancer diagnosis. Such a strategy is based on the joint use of microwaves, as a non-invasive and non-toxic tool to probe cancer lesions, and of Magnetic NanoParticles (MNP). These latter are used as a biocompatible contrast agent able to selectively enhance the response of cancerous tissues by modifying their magnetic permeability. Key aspects of the strategy are the possibility to modulate the magnetic response of MNP by using a polarizing magnetic field and the capabilities of avoiding ambiguities in discriminating between cancerous and healthy tissues. This contribution aims at providing a feasibility assessment of this new methodology in quasi realistic conditions. To this purpose, a numerical analysis has been carried out, in which the MNP behavior has been modeled according to the results of an experimental characterization and the imaging problem has been simulated by considering malignant lesions lying into an anthropomorphic 3D breast phantom.

The paper deals with Magnetic NanoParticle Hyperthermia and aims at assessing the effectiveness of an optimization criterion for the choice of the exposure conditions and nanoparticle characteristics, recently proposed by some of the authors, in the more realistic case of electrically and thermally inhomogeneous tissues. Numerical results are reported, showing the effectiveness of the criterion in the case of spherical tumor embedded in multi-layered tissues of cylindrical shape

The paper presents a novel measurement method for the broadband characterization of the electromagnetic properties of diluted water-based ferrofluids. The approach exploits the possibility of switching ON and OFF the magnetic response of the suspended magnetic nanoparticles, without affecting the electric response of the ferrofluid, by means of an applied polarizing magnetostatic field. In such a way, two different datasets are collected: 1) the OFF data, which only depend on the electric response of the investigated ferrofluid; 2) the ON data, which depend on both the electric and magnetic responses of the ferrofluid. These data, properly processed, allow the physical separation, at the measurement stage, of the electric response from the magnetic one and so a more robust and stable inversion process, especially in the case of diluted water-based ferrofluids. The reported results show the robustness of the approach as compared to standard measurement techniques.

The main aim of this paper is to set the theoretical framework needed for the analysis and design of magnetically driven nanomachines, namely, hybrid nanosystems obtained by assembling macromolecular complexes and magnetic nanoparticles (MNPs), whose functions can be activated and controlled by means of magnetic fields (MFs). Starting from the theoretical models, which describe the dynamics of an MNP in an applied MF, simplified analytical tools enabling to accurately describe the mechanical interactions between the nanoparticle and the applied field are derived. Exploiting these tools, the limits theoretically achievable by using MNPs as nanomotors, as well as the features of the nanoparticle and the MF required for this purpose, are determined. Then, three simple magnetically driven nanomachines of potential practical interest are considered, and their feasibility is analyzed, taking into account the presence of the thermal agitation.

In this paper, a microwave technique for breast cancer imaging is presented. The approach is based on the use of magnetic nanoparticles as contrast agent to induce a nonnull magnetic contrast selectively localized within the tumor. This allows us to face cancer imaging as the reconstruction of a magnetic contrast from the corresponding scattered field. To extract, from the measured data the contribution due to the magnetic contrast, i.e., the signal meaningful for cancer imaging, the approach exploits the possibility of modulating the magnetic response of magnetic nanoparticles by means of a polarizing magnetic field. The achievable reconstruction capabilities and the robustness against uncertainties on the electric features of the surrounding electric scenario are assessed by means of numerical examples.

Purpose: Two points are particularly relevant for the clinical use of magnetic nanoparticle hyperthermia: the optimisation of both the exposure conditions and the magnetic nanoparticle characteristics, and the assessment of the limits of scalability of the treatment. To answer these two points a criterion for the individuation of the magnetic field parameters and of the magnetic nanoparticle features that minimise the therapeutic concentration of nanoparticles to be used in magnetic nanoparticle hyperthermia is developed. Methods: The proposed criterion is based on the estimation of the levels of heat generation rate, due to the electromagnetic field, to be supplied to both the cancerous and the neighbouring healthy tissues for achieving the therapeutic heating of the tumour with a desired degree of spatial selectivity. These quantities are determined by exploiting the Pennes bioheat transfer model. Results: The reliability of the criterion has been proven by means of an extensive numerical analysis, performed by considering tumours of spherical shape embedded in tissues of cylindrical shape. Several cases, including tumours of different sizes and position have been considered. Conclusions: By exploiting the proposed criterion a study of the clinical scalability of the therapeutic approach is presented.

This paper presents the results of a broadband spectroscopy study, over the frequency range 1 MHz–2 GHz, of the electromagnetic properties of a ferrofluid consisting of magnetite nanoparticles, with a mean magnetic size of 10 nm, dispersed in water. An innovative measurement approach and apparatus, allowing an accurate determination of the permeability, even in presence of a large permittivity, have been developed to characterize the suspension. The results obtained show a significant magnetic response over the whole analyzed frequency range, with a good agreement with the theoretical models describing the magnetization dynamics of these systems. Moreover, a strong dielectric response has been detected, which is in satisfactory agreement with the models developed to describe the dielectric behavior of charged nanoparticles suspended in aqueous solution. This result implies that measurement techniques able to determine both the permittivity and permeability become mandatory for a reliable determination of the magnetic properties of aqueous ferrofluids. The accuracy of the determined permeability spectrum is estimated to be of the order of few percent, so these results provide a reliable experimental basis to estimate how fruitful the use of magnetic nanoparticles can be in relevant biomedical applications.

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.