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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.

International audience; This work focuses on brain stroke imaging via microwave technology. In particular, the open issue of monitoring patients after stroke onset is addressed here in order to provide clinicians with a tool to control the effectiveness of administered therapies during the follow-up period. In this paper, a novel prototype is presented and characterized. The device is based on a low-complexity architecture which makes use of a minimum number of properly positioned and designed antennas placed on a helmet. It exploits a differential imaging approach and provides 3D images of the stroke. Preliminary experiments involving a 3D phantom filled with brain tissue-mimicking liquid confirm the potential of the technology in imaging a spherical target mimicking a stroke of a radius equal to 1.25 cm.

Brain stroke is one of the most common diseases worldwide. Magnetic resonance imaging and computerized tomography are currently the two most assessed and reliable diagnostic tools, of great support to the clinicians. However, these devices are costly, time consuming and not portable, so that they are not appropriate for bedside monitoring. Hence, there is an increasing worldwide interest to develop complementary techniques to continuously monitor a patient after the stroke onset. In this paper, we report about the experimental testing of a novel device able to monitor cerebrovascular diseases, whose realization is based on microwave imaging technology. A 2-D version of the device has been fully experimentally tested and its 3-D version is under development.

Magnetic nanoparticles (MNP) enhanced microwave imaging could provide an effective approach for an early stage diagnosis of breast cancer, if encouraging results coming from accurate and realistic numerical studies are confirmed by an experimental proof of concept framework. To this end, an ad hoc laboratory setup has been designed and built up to verify the possibility of detecting the low signal scattered by MNP when embedded into a simplified but realistic breast phantom. This paper describes the developed measurement setup and the results coming from a first run of experiments, which confirm the possibility to detecting realistic amounts of accumulated nanoparticles. Moreover, the experimental results analysis allows addressing the future developments required to determine the ultimate detection limits of the technique, giving relevant information to plan the preclinical assessment.

The aim of this paper is to present and experimentally verify the first prototype of a microwave imaging system specifically designed and realized for the continuous monitoring of patients affected by brain stroke, immediately after its onset and diagnosis. The device is a 2D version of the 3D system, currently under construction, and consists of an array of 12 printed monopole antennas connected to a two-port vector network analyzer through a switching matrix so that each antenna can act as a transmitter or receiver, thereby allowing the acquisition of the entire multistatic multiview scattering matrix required for the imaging. The system has been experimentally tested on 2D phantoms with electric properties mimicking the brain. The presence and the evolution of the stroke have been reproduced by filling a proper cavity in the phantom with a liquid having the electric properties of blood. A differential approach has been adopted by acquiring the scattering matrix before and after the filling of the blood cavity. The so achieved differential dataset has been processed by means of a linear imaging algorithm in order to reconstruct the stroke location and dimension. Moreover, the effect of pre- and postprocessing operations on the measured data is investigated. A good agreement has been obtained between the reconstructions and the actual scenario. As a final remark, it is worth noting that the entire data acquisition and processing are sufficiently fast to allow a real-time monitoring.

This paper presents the design of a novel low-complexity microwave imaging system for monitoring brain stroke. In particular, the design is concerned with the determination of the optimal layout of the antennas array, namely, minimum number, positions, and polarization of the radiating elements, enabling the acquisition of an amount of data such to assure a reliable imaging. This goal is achieved by adopting a rigorous design procedure based on the inspection of the singular value decomposition of the relevant discretized scattering operator and taking into account the actual dynamics and signal-to-noise ratio of the measurement system. The design is first carried out in the case of ideal dipoles and then extended and assessed for actual printed monopole antennas, developed for the imaging system. The resulting system is a helmet equipped with 24 antennas, whose performances have been numerically validated in terms of both spatial resolution and reconstruction capabilities, by employing full-wave numerical simulations, realistic 3-D phantoms of the human head, and an accurate modeling of the actual antennas employed in the system.

Magnetic nanoparticles have been recently proposed as a contrast agent for breast cancer microwave imaging. In this communication, we report on the ongoing activities aiming at the feasibility validation of magnetic nanoparticles enhanced microwave imaging. In particular, we discuss the results of some experiments, carried out to deal with the factors that influence the detection limits of the technique. Previous experiments have shown that a major limitation to the minimum amount of contrast agent that can be appreciated is due to the instrumental drift, which cannot be overcome by simply averaging the measurements. In addition, owing to the low level of the useful signal, possible magnetic effects arising from the system and the involved media can become relevant and impair the measurements. In the following, we deal with these aspects and present the results of a first set of experiments aimed at assessing the detection capabilities of the technique.

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.

The use of contrast agents is gaining a huge interest in microwave imaging (MWI) of breast cancer [1]–[3] in order to discriminate the response of cancerous tissues from that of the surrounding healthy tissue, and so to reduce the occurrence of false negatives arising from the low contrast between the electric properties of cancerous and fibro-glandular tissues [4]. To this end, magnetic nanoparticles (MNPs) represent a viable and effective choice [5], [6]. Indeed, they are allowed for clinical use and can be functionalized with biological molecules able to selectively bind to cancerous cells. Moreover, the microwave magnetic response of the MNPs can be properly modulated by applying an external polarizing magnetic field (PMF), without significantly influencing the response of the surrounding healthy tissue. As a result, by exploiting a proper differential measurement strategy, one can separate the response of the background from that of the MNPs (i.e., the “useful” signal), which, if present, is unambiguously associated to the presence of a malignant lesion [5].

This paper deals with the optimal design of phased arrays for medical applications of microwaves, such as hyperthermia treatments and cancer imaging. To address this problem, microwave engineers have to face peculiar and novel challenges, since the region of interest is a 3-D domain in the near field of the array and consists of a highly heterogeneous and lossy medium, whose characteristics change from patient to patient. For this reason, we have to reconsider basic fundamentals about phased array design, in order to devise proper tools and criteria. In particular, we address the design of the system layout, i.e., the choice of the number and locations of the array elements, as this represents the preliminary fundamental problem to face. To this end, we first formulate the two general problems relevant to biomedical applications--the design of an array for therapeutic purposes and of an array for diagnostic/imaging goals. We then address the proper theoretical and analytic tools and methods that enable pursuit of an optimal design with respect to given constraints. Finally, we provide some examples to show how the design procedure can be carried out in practice.

A new technique, exploiting magnetic nanoparticles as contrast agent, has been recently proposed for microwave breast cancer imaging. As human tissues are non magnetic, the adoption of a magnetic contrast agent, able to selectively target tumoral cells, represents an effective means to increase diagnostic reliability. Although the effectiveness of the new technique has been fully assessed through realistic and accurate numerical simulations, an experimental proof-of-concept is still needed to set the ground for a subsequent pre-clinical stage. In this communication, we present the first results of such an experimental validation, performed with an ad hoc designed laboratory set-up and exploiting a realistic (although simplified) breast phantom.

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.

Magnetic nanoparticles-enhanced microwave imaging has been recently proposed to overcome the limitations of conventional microwave imaging methods for breast cancer monitoring. In this paper, we discuss how to tackle the linear inverse scattering problem underlying this novel technique in an effective way. In particular, our aim is to minimize the required a priori patient-specific information, avoid occurrence of false positives, and keep the computational burden low. By relying on an extensive numerical analysis in realistic conditions, we show that the method can provide accurate and reliable images without information on the inner structure of the inspected breast and with an only rough knowledge of its shape. Notably, this allows moving to an offline stage the computationally intensive part of the image formation procedure. In addition, we show how to appraise the total amount of magnetic contrast agent targeted in the tumor. © 1964-2012 IEEE.

The communication deals with Microwave Imaging (MWI) of breast cancer and aims at investigating the feasibility of an approach, recently proposed, which exploits Magnetic Nanoparticles (MNP) as magnetic contrast agents selectively delivered to the tumor. The numerical study herein presented is mainly devoted to test the reconstruction capabilities of the approach in quasi realistic conditions. To this purpose, 3D anthropomorphic breast phantom and an experimental characterization of the MNP response have been considered.

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.

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.