238 research outputs found
Electromagnetic device for imaged guided microwave ablation
Get PDFThis dissertation demonstrates the design of a microwave imaging system for monitoring liver thermal ablation treatments.
Liver cancer is the third most deadly cancer worldwide and has an increasing yearly fatality rate. Liver thermal ablation is considered to be an effective alternative to conventional treatment methods such as surgery. However, over the years, real-time monitoring of liver thermal ablation has become a big challenge because the existing modalities like computed tomography (CT), magnetic resonance imaging (MRI), positron emission tomography (PET), and Ultrasound imaging (US) have limitations in the applications at hand, that make them incapable or not suitable of providing real-time temperature values. Therefore, the assessment of the ablation procedure heavily relies on the clinician’s experience. Microwave imaging (MWI) is a potential candidate for this clinical need, since it provides a map of the dielectric properties of an unknown target from the knowledge of the scattered electromagnetic field. In fact, during liver thermal ablation treatments, the water molecules in the ablation zone dramatically reduce due to the heating. This process yields a change in dielectric properties values in the ablation zone as compared to the un-treated liver. The principle of microwave imaging for thermal ablation monitoring is to take advantage of the dielectric properties contrast between the ablated zone and the un-treated liver tissue. In fact, by recording and processing the scattered field at different stages of the treatment, it should be possible to image the evolution of the dielectric properties in the domain of interest. According to existing knowledge of the correspondence between liver’s dielectric properties values and temperature, it would then be possible to derive the local temperature in the ablation zone and hence determine the ablation stage.
Among the advantages of MWI for thermal ablation monitoring, it could be cited the low-cost, portability, capability of real-time imaging, harmless nature, as exploitation of low-power, non-ionizing radiation. Thanks to these circumstances. MWI has been considered for a number of biomedical applications, such as breast imaging, brain imaging, bone imaging, etc.
A microwave imaging system for monitoring liver thermal ablation treatment would be made by an array of antennas embedded into a coupling medium and located in close proximity to the human abdomen, in front of the area to be treated.
In this research, firstly, a numerical analysis was performed to determine the optimal working conditions in terms of operating frequency and coupling medium dielectric properties. Additionally, the dielectric properties of healthy ex vivo liver, as well as thermally ablated one were measured. Secondly, the antennas in the microwave imaging system were designed within the proposed working condition. Studies were performed with different antenna substrate materials looking for the most compact design. Three different antipodal Vivaldi antennas were designed and compared. After the microwave antenna design was completed, an in-silico assessment of the experimental set-up was performed, to define the optimal number of antennas and their spacing. The optimized set-up consists of eight antennas arranged in a staggered two-rows antennas array configuration immersed inside the coupling medium. Then, a simple yet representative experimental set-up for the validation of the imaging system was studied. The set-up foresees the 8 antennas inserted inside a tank filled with the coupling material; in front of the antenna array, a 3-D printed ellipsoidal phantom filled with tissue-mimicking liquid represents the thermally ablated zone. The retrieved images inside the domain of interest show that the designed system can detect the position of the ablated zone and identify it at different ablation stages. Finally, the chosen antenna was realized and experimentally verified, and a recipe to realize the coupling material was proposed and experimentally tested. Ultimately, the system was experimentally assessed with one antenna mechanically moved in a linear motion measuring the signal in front of the 3-D printed phantom. The numerical and experimental assessment of the microwave imaging system verifies the feasibility of such a system for liver ablation monitoring.
This study paves the way for the real-time monitoring of liver thermal ablation through microwave imaging techniques
Hyperthermia Treatment Monitoring via Deep Learning Enhanced Microwave Imaging: A Numerical Assessment
Get PDFSimple Summary Non-invasive temperature monitoring during hyperthermia cancer treatment is of paramount importance. It allows physicians to verify the therapeutic temperature is reached in the treated area. Currently, only superficial or invasive thermometry is performed on a clinical level. Magnetic resonance thermometry has been proposed as a a non-invasive alternative but its applicability is limited. Conversely, microwave imaging based thermometry is a potential low cost candidate for non-invasive temperature monitoring. This works presents a computational study in which the use of deep learning is proposed to face the challenges related to the use of microwave imaging in hyperthermia monitoring. The paper deals with the problem of monitoring temperature during hyperthermia treatments in the whole domain of interest. In particular, a physics-assisted deep learning computational framework is proposed to provide an objective assessment of the temperature in the target tissue to be treated and in the healthy one to be preserved, based on the measurements performed by a microwave imaging device. The proposed concept is assessed in-silico for the case of neck tumors achieving an accuracy above 90%. The paper results show the potential of the proposed approach and support further studies aimed at its experimental validation
An Effective Framework for Deep-Learning-Enhanced Quantitative Microwave Imaging and Its Potential for Medical Applications
Get PDFMicrowave imaging is emerging as an alternative modality to conventional medical diagnostics technologies. However, its adoption is hindered by the intrinsic difficulties faced in the solution of the underlying inverse scattering problem, namely non-linearity and ill-posedness. In this paper, an innovative approach for a reliable and automated solution of the inverse scattering problem is presented, which combines a qualitative imaging technique and deep learning in a two-step framework. In the first step, the orthogonality sampling method is employed to process measurements of the scattered field into an image, which explicitly provides an estimate of the targets shapes and implicitly encodes information in their contrast values. In the second step, the images obtained in the previous step are fed into a neural network (U-Net), whose duty is retrieving the exact shape of the target and its contrast value. This task is cast as an image segmentation one, where each pixel is classified into a discrete set of permittivity values within a given range. The use of a reduced number of possible permittivities facilitates the training stage by limiting its scope. The approach was tested with synthetic data and validated with experimental data taken from the Fresnel database to allow a fair comparison with the literature. Finally, its potential for biomedical imaging is demonstrated with a numerical example related to microwave brain stroke diagnosis
A Simple Differential Microwave Imaging Approach for In-Line Inspection of Food Products
Get PDFMicrowave imaging has been recently proposed as alternative technology for in-line inspection of packaged products in the food industry, thanks to its non-invasiveness and the low-cost of the equipment. In this framework, simple and effective detection/imaging strategies, able to reveal the presence of foreign bodies that may have contaminated the product during the packaging stage, are needed to allow real-time and reliable detection, thus avoiding delays along the production line and limiting occurrence of false detections (either negative or positive). In this work, a novel detection/imaging approach meeting these requirements is presented. The approach performs the detection/imaging of the contaminant by exploiting the symmetries usually characterizing the food items. Such symmetries are broken by the presence of foreign bodies, thereby determining a differential signal that can be processed to reveal their presence. In so doing, the approach does not require the prior measurement of a reference, defect-free, item. With respect to the quite common case of homogeneous food packaged in circular plastic/glass jars, numerical analyses are provided to show the effectiveness of the proposed approach
Microwave Imaging System for In-Line Security Assessment
Get PDFThe accidental foreign bodies contamination is still a major issue for food manufacturing industries. The continuous growth of automation along production lines together with the increasing attention of the customers towards food products quality, improved the industries care aiming to avoid complaints and ensure the best possible quality. As a matter of fact, several technologies are employed, but they lack in detecting certain class of contaminants, such as low-density plastics or small glass fragments that could turn into a severe threat, in particular for children. This work proposes a microwave imaging system in order to overcome these limitation in employed technologies.
The design and characterization are reported in this paper; the simulations are addressed to the realization of a system prototype
Microwave Imaging Device for In-Line Food Inspection
Get PDFForeign body contamination is a key issue in food production and packaging industries. The constant increase of mechanized process chain, the variety of materials employed during the production and the growing consumer awareness about food quality arose the number of complaints in the recent years. Several technologies are applied to ensure that products are free from contaminations, but they may fail in detecting low-density plastic or glass fragments contaminants accidentally present inside food/beverage products. To address this issue, a system exploiting microwave imaging is proposed and assessed in this work. To this end, we designed a system which is capable of monitoring of packaged food along the production line, taking into account the specific and challenging constraints arising in such a scenario. Its design and full characterization with full-wave simulation are reported in the paper. The obtained results set the ground for the realization of the prototype of the system
Slot-loaded Antipodal Vivaldi Antenna for a Microwave Imaging System to Monitor Liver Microwave Thermal Ablation
No full textThis study presents the design and the
experimental validation of a slot-loaded antipodal Vivaldi
antenna for a microwave imaging system to monitor liver
microwave thermal ablation. The antenna’s overall dimension
is equal to 40mm×65mm, and its working bandwidth goes from
600 MHz up to 3 GHz, with the possibility to operate at a higher
frequency. The antenna is designed to operate inside a coupling
medium that allows to scale down the antenna dimensions, as
well as to improve the coupling of the electromagnetic power to
the tissue. The antenna’s S-parameters well agree with the
simulation result. Finally, the antenna proposed in this work
shows the most compact aperture dimension, as compared with
other similar antennas designed for biomedical applications,
working within the same bandwidth
On the Design of Phased Arrays for Medical Applications
No full textThis 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 review on ground penetrating radar technology for the detection of buried or trapped victims
No full textThe localization of people buried or trapped under snow or debris is an emerging field of application of ground penetrating radar (GPR). In the last years, technological solutions and processing approaches have been developed to improve detection accuracy, speed up localization, and reduce false alarms. As such, GPR can play an active role in cooperative approaches required to tackle such emergencies. In this work, we present and briefly analyze the evolution of research in this field of application of GPR technology. In doing so, we adopt a point of view that takes into account that avalanches and collapsed buildings are two scenarios that call for different GPR approaches, since the former can be tackled through image processing of radar data, while the latter rely on the detection of the Doppler frequency changes induced by physiological movements of survivors, such as breathing. © 2014 IEEE
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