Papers by N. Joachimowicz
Non Destructive Control of Fruit Quality using Microwaves
HAL (Le Centre pour la Communication Scientifique Directe), Oct 10, 2019
Optimized antenna array layout in a microwave imaging system for brain stroke monitoring
12th European Conference on Antennas and Propagation (EuCAP 2018), 2018
This paper presents the design of the layout of the radiating part of a microwave imaging system ... more This paper presents the design of the layout of the radiating part of a microwave imaging system for brain stroke monitoring. The radiating part of the system is constituted by an array of antennas placed tangent to a surface conformal to the upper part of head and the design procedure addresses the positioning and the number of the array elements. To this end, an analysis of the relevant scattering operator is performed, taking into account the limited dynamic of the measurement system and the limited number of implemented antennas. Finally, a preliminary tomographic image of a hemorrhagic stroke obtained with synthetic data is reported.
Experimental assessment of qualitative microwave imaging using a 3-D realistic breast phantom
2017 11th European Conference on Antennas and Propagation (EUCAP), 2017
In this work we present an experimental study of qualitative microwave imaging algorithms for bre... more In this work we present an experimental study of qualitative microwave imaging algorithms for breast cancer detection. All the experiments are carried out with a 3-D printed realistic breast phantom filled with designed tissue mimicking liquids. In the following, the first experimental results using the Truncated Singular Value Decomposition (TSVD) scheme and the Linear Sampling Method (LSM) reconstructions are reported.
2-D Experimental Testing of a Microwave Imaging System Designed for Cerebrovascular Diseases Monitoring
2019 13th European Conference on Antennas and Propagation (EuCAP), 2019
This paper describes the performed 2-D experimental testing on a microwave imaging system, design... more This paper describes the performed 2-D experimental testing on a microwave imaging system, designed for cerebrovascular diseases monitoring. Two different imaging algorithms have been implemented and compared. A good agreement between the reconstructed images and the real target position and size has been obtained.
Damaged Apple Sorting With mmWave Imaging and Nonlinear Support Vector Machine
IEEE Transactions on Antennas and Propagation, 2020
This article is a proof of concept proposing and describing a complete workflow to differentiate ... more This article is a proof of concept proposing and describing a complete workflow to differentiate healthy from damaged apples, starting with millimeter-wave (mmWave) measurements and ending with a classification based on support vector machine (SVM). The method has proven to be successful with only 6% error when scan angle and frequency diversity are used. In a first step, we build a database of more than 1800 images obtained by processing measurements with a 2-D fast Fourier transform. Images are then converted to binary and used as the input to a nonlinear SVM. At this stage, 90% of the database is used for training, and coefficients <inline-formula> <tex-math notation="LaTeX">${C}$ </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">$\gamma $ </tex-math></inline-formula> are tuned to minimize the error. The remaining 10% of images are used for testing. In a second step, we assess and discuss the influence of the physical inputs of the database: the frequency, the sparsity of measurement points, and the size of the apples. Finally, we explore new scenarios considering other fruits.
Quantitative Reconstruction of Complex Permittivity Distributions by Means of Microwave Tomography
Inverse Problems and Theoretical Imaging, 1990
This paper concerns an iterative method for solving an inverse electromagnetic scattering problem... more This paper concerns an iterative method for solving an inverse electromagnetic scattering problem: the quantitative reconstruction of complex permittivity distribution of inhomogeneous objects. During the last decade, intensive research and interest have been focussed on reconstruction algorithms based on the so-called Diffraction Tomography with applications in microwaves or ultrasound [1–16]. The main motivations for using such approaches are to obtain explicit formulas for solving the imaging problem, to take advantage of existing numerical algorithms (Fast Fourier Transform) and to implement the algorithms on PC’s or minicomputers for imaging system purposes (planar microwave camera [5], experiments with ultrasounds and microwaves [11][13][14][16], cylindrical microwave system [15]). However, Diffraction Tomography is subjected to various limitations which include artefacts due to diffraction effects in strongly inhomogeneous media [7][10][16][17][18].The final objective of microwave imagery is to determine the complex permittivity profile (permittivity and conductivity profiles) of the object under investigation. An increasing number of papers [17–25] have been devoted to a such non-linear inverse problem. Different solutions based on Moment Methods [19–25] have been explored, but, convergence depends on contrasting objects. Furthermore, stability is very sensitive to the observation point locations and measurement accuracy (due to the ill-conditioning of the matrix which has to be inverted). Stability and sensivity are why the use of an iterative scheme is important: effects of ill-conditioning can be significantly reduced by enforcing the convergence with “a priori” information (object external shape, upper and lower bounds of complex permittivity, presence of different media,…). Concerning the uniqueness of object reconstruction, it has been proved [24] that if the background medium is dissipative, then the inverse scattering problem has a unique solution.
Two iterative methods for quantitative reconstruction of complex permittivity in microwave tomography
SPIE Proceedings, 1990
Abstract not available.
In this paper an experimental prototype of a robot controlled data acquisition system for microwa... more In this paper an experimental prototype of a robot controlled data acquisition system for microwave imaging is presented, where the transmitting and receiving antennas are immersed in a water-tank. The scattered field from the object under test is acquired by using the robot and scanning a single receiving antenna in cylindrical or half spherical coordinates, while the transmitting antenna is
2021 15th European Conference on Antennas and Propagation (EuCAP)
In this paper we study the numerical modeling of the complex anthropomorphic human phantoms, aime... more In this paper we study the numerical modeling of the complex anthropomorphic human phantoms, aimed for microwave imaging, using the WIPL-D software. By comparing various models, we investigate the influence of the geometrical simplification of the phantom on the accuracy of the electromagnetic response of the antennas in the vicinity of the phantom. By controlling the geometrical deviation of the simplified model with respect to the original model, we show that it is possible to reduce the simulation resources for one to two orders of magnitude while preserving the precision of the electromagnetic analysis.
Reference phantoms for microwave imaging
2017 11th European Conference on Antennas and Propagation (EUCAP), 2017
Microwave imaging offers an alternative modality for breast cancer screening and for the diagnosi... more Microwave imaging offers an alternative modality for breast cancer screening and for the diagnosis of cerebrovascular accidents. Before clinical application, the performances of microwave imaging systems have to be assessed on anatomically detailed anthropomorphic phantoms. This paper presents advances in the development of breast and head phantoms based upon 3D-printed structures filled up with liquid solutions that mimic the biological tissues in terms of complex permittivity in a broad microwave frequency band.
A feasibility study for cerebrovascular diseases monitoring via microwave imaging
2017 International Conference on Electromagnetics in Advanced Applications (ICEAA), 2017
With this paper, we will report about the feasibility study of a novel device which will be capab... more With this paper, we will report about the feasibility study of a novel device which will be capable of performing the follow-up of a brain stroke event in the post-acute stage. The underlying technology, used in the device under design, is microwave imaging, which exploits the difference in dielectric properties of tissues. Numerical full-wave simulations, with realistic 3-D phantoms of the human head, will show the potential capabilities of the microwave imaging device.
Easy-to-produce adjustable realistic breast phantoms for microwave imaging
2016 10th European Conference on Antennas and Propagation (EuCAP), 2016
This paper deals with the development of realistic breast phantoms dedicated to microwave imaging... more This paper deals with the development of realistic breast phantoms dedicated to microwave imaging for breast tumor detection. The phantoms are based upon 3D-printed structures filled up with different liquid mixtures that mimic the various breast tissue types (healthy or cancerous) in terms of complex permittivity over a broad microwave frequency band.
Experimental Validation of a Microwave Brain Scanner for Cerebrovascular Diseases Monitoring
2019 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting, 2019
Brain stroke is one of the most common diseases worldwide. Magnetic resonance imaging and compute... more 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.
Ongoing Developments Towards the Realization of a Microwave Device for Brain Stroke Monitoring
2018 IEEE International Symposium on Antennas and Propagation & USNC/URSI National Radio Science Meeting, 2018
The present paper describes our on-going work towards the realization of a novel device to perfor... more The present paper describes our on-going work towards the realization of a novel device to perform continuous monitoring of a patient after a stroke onset. The realization of the antenna array and of the control electronics will be discussed, together with a first experimental test of the system.
This work describes the realization, characterization and first experimental validation of a nove... more This work describes the realization, characterization and first experimental validation of a novel portable device for brain stroke monitoring via microwave imaging. A low-complexity approach is the base for the cited device. The 24 antennas are distributed on a surface conformal to the human head, as a helmet. The initial validation of the system is performed through a set of experiments on a 3-D anatomically realistic phantom.
Microwave Imaging II: Diffraction Tomography
2019 13th European Conference on Antennas and Propagation (EuCAP), 2019
This paper shows that the manufacturing process presented in our previous work which was used for... more This paper shows that the manufacturing process presented in our previous work which was used for building time-stable and remotely reproducible breast and head phantoms, opens up new avenues for mimicking any types of biological tissues in the frequency range of [500 MHz – 3 GHz]. Moreover, the numerical version of the phantom (STL format file) enables us to test its conformity, as well as experimental configurations. The study is placed in the framework of the European project EMERALD.
2021 International Conference on Electromagnetics in Advanced Applications (ICEAA), 2021
The Journal of Photographic Science, 1991
Comparison between three integral formulations for the 2D-TE scattering problem
Digest on Antennas and Propagation Society International Symposium
The fast Fourier transform conjugate gradient method solves numerically the electric field integr... more The fast Fourier transform conjugate gradient method solves numerically the electric field integral equation, using the method of moments with pulse basis function and point matching, but substantial errors are found in this method for the 2-D TE case. In the present work, the authors analyze the source of errors in these approximations and show that the modified method empirically proposed by D.T. Borup, D.M. Sullivan, and O.P. Ghandi (IEEE Trans. Microwave Theory Tech., vol.MTT-35, p.383-95, Apr.1987) would not have been necessary if correct terms in the integral equation were used. With this aim, the authors propose a new integral formulation using generalized functions and compare it with two previous formulations, that of S.C. Hill, C.H. DAmey, and D.A. Christensen Radio Sci., vol.18, p.328-36, May-June 1983 and D.E. Livesay and K.M. Chen (IEEE Trans. Microwave Theory Tech., vol.MMT-22, p.1273-80, 1974). For all the numerical methods discussed, the conjugate gradient technique is used to solve the linear system, and the convolution products are computed by means of a Fourier transform. The results are of interest in connection with refining numerical methods to support biomedical applications (e.g. microwave imaging and hypothermia treatment).<<ETX>>
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Papers by N. Joachimowicz