Nadine Joachimowicz

Bio: Nadine Joachimowicz is an academic researcher from University of Paris. The author has contributed to research in topics: Microwave imaging & Imaging phantom. The author has an hindex of 16, co-authored 33 publications receiving 1349 citations. Previous affiliations of Nadine Joachimowicz include Supélec & Pierre-and-Marie-Curie University.

Inverse scattering: an iterative numerical method for electromagnetic imaging

Abstract: The authors propose a spatial iterative algorithm for electromagnetic imaging based on a Newton-Kantorovich procedure for the reconstruction of the complex permittivity of inhomogeneous lossy dielectric objects with arbitrary shape. Starting from integral representation of the electric field and using the moment method, this technique has been developed for 2-D (for TM and TE polarization cases) objects as well as for 3-D objects. Its performance has been compared with spectral techniques of classical diffraction tomography, the modified Newton method, and the pseudo-inverse method. >

Microwave imaging-complex permittivity reconstruction-by simulated annealing

Abstract: A preliminary study of the application of simulated annealing (SA) to complex permittivity reconstruction in microwave tomography is presented. Reconstructions of a simplified model of a human arm obtained with simulated noise-free data are presented for three different methods: SA, quenching, and a Newton-Kantorovich method. These results show that SA can converge to an accurate solution in cases where the two deterministic methods fail. For this reason SA can be used to get closer to the final solution before applying a faster deterministic method. >

Diffraction tomography: contribution to the analysis of some applications in microwaves and ultrasonics

Abstract: After a brief presentation of the principles of diffraction tomography, the authors focus on the applications they have investigated in the biomedical and non-destructive testing domains. Typical numerical and experimental results are presented and in their comments they state what they think are the current limitations of this approach and the possible opportunities for future work with this imaging technique.

Quantitative Microwave Imaging for Breast Cancer Detection Using a Planar 2.45 GHz System

Abstract: Microwave imaging is recognized as a potential candidate for biomedical applications, such as breast tumor detection. In this context, the capability of a planar microwave camera to produce quantitative imaging of high-contrast inhomogeneous objects is investigated. The image reconstruction is achieved by means of an iterative Newton-Kantorovich algorithm. Promising numerical simulation results indicate that the planar geometry is suitable for quantitative imaging, as long as the signal-to-noise ratio is higher than 40 dB. Such a requirement is satisfied with the camera due to appropriate data averaging. Furthermore, different calibration techniques are discussed, aiming to reduce the model error, which results from the limitations of the numerical model involved in the reconstruction to accurately reproduce the experimental setup. The experimental work also includes the development of a phantom using a new fluid tissue equivalent mixture based on Triton X-100. As a final result, this paper shows the first reconstructed quantitative images of a high-contrast inhomogeneous 2-D object obtained by using experimental data from the camera.

Convergence and stability assessment of Newton-Kantorovich reconstruction algorithms for microwave tomography

Abstract: For newly developed iterative Newton-Kantorovitch reconstruction techniques, the quality of the final image depends on both experimental and model noise. Experimental noise is inherent to any experimental acquisition scheme, while model noise refers to the accuracy of the numerical model, used in the reconstruction process, to reproduce the experimental setup. This paper provides a systematic assessment of the major sources of experimental and model noise on the quality of the final image. This assessment is conducted from experimental data obtained with a microwave circular scanner operating at 2.33 GHz. Targets to be imaged include realistic biological structures, such as a human forearm, as well as calibrated samples for the sake of accuracy evaluation. The results provide a quantitative estimation of the effect of experimental factors, such as temperature of the immersion medium, frequency, signal-to-noise ratio, and various numerical parameters.

Reconstruction of two-dimensional permittivity distribution using the distorted Born iterative method

Abstract: The distorted Born iterative method (DBIM) is used to solve two-dimensional inverse scattering problems, thereby providing another general method to solve the two-dimensional imaging problem when the Born and the Rytov approximations break down. Numerical simulations are performed using the DBIM and the method proposed previously by the authors (Int. J. Imaging Syst. Technol., vol.1, no.1, p.100-8, 1989) called the Born iterative method (BIM) for several cases in which the conditions for the first-order Born approximation are not satisfied. The results show that each method has its advantages; the DBIM shows faster convergence rate compared to the BIM, while the BIM is more robust to noise contamination compared to the DBIM. >

A contrast source inversion method

Abstract: This paper describes a simple algorithm for reconstructing the complex index of refraction of a bounded object immersed in a known background from a knowledge of how the object scatters known incident radiation. The method described here is versatile accommodating both spatially and frequency varying incident fields and allowing a priori information about the scatterer to be introduced in a simple fashion. Numerical results show that this new algorithm outperforms the modified gradient approach which until now has been one of the most effective reconstruction algorithms available.

A clinical prototype for active microwave imaging of the breast

Abstract: Despite its recognized value in detecting and characterizing breast disease, X-ray mammography has important limitations that motivate the quest for alternatives to augment the diagnostic tools that are currently available to the radiologist. The rationale for pursuing electromagnetic methods is strong given the data in the literature, which show that the electromagnetic properties of breast malignancy are significantly different than normal in the high megahertz to low gigahertz spectral range, microwave illumination can effectively penetrate the breast at these frequencies, and the breast is a small readily accessible tissue volume, making it an ideal site for deploying advanced near-field imaging concepts that exploit model-based image reconstruction methodology. In this paper a clinical prototype of a microwave imaging system, which actively illuminates the breast with a 16-element transceiving monopole antenna array in the 300-1000 MHz range, is reported. Microwave exams have been delivered to five women through a water-coupled interface to the pendant breast with the participant positioned prone on an examination table. This configuration has been found to be a practical, comfortable approach to microwave breast imaging. Sessions lasted 10-15 min per breast and included full tomographic data acquisition at seven different array heights beginning at the chest wall and moving anteriorly toward the nipple for seven different frequencies at each array position. This clinical experience appears to be the first report of active near-field microwave imaging of the breast and is certainly the first attempt to exploit model-based image reconstructions from in vivo breast data in order to convert the measured microwave signals into spatial maps of electrical permittivity and conductivity. While clearly preliminary, the results are encouraging and have supplied some interesting findings. Specifically, it appears that the average relative permittivity of the breast as a whole correlates with radiologic breast density categorization and may be considerably higher than previously published values, which have been based on ex vivo tissue specimens.

Enhancing breast tumor detection with near-field imaging

Abstract: This article outlines the main features of active, passive, and hybrid systems under investigation for breast cancer detection. Our main focus is on active microwave systems, in particular microwave tomography and confocal microwave imaging.

Inverse scattering: an iterative numerical method for electromagnetic imaging

Abstract: The authors propose a spatial iterative algorithm for electromagnetic imaging based on a Newton-Kantorovich procedure for the reconstruction of the complex permittivity of inhomogeneous lossy dielectric objects with arbitrary shape. Starting from integral representation of the electric field and using the moment method, this technique has been developed for 2-D (for TM and TE polarization cases) objects as well as for 3-D objects. Its performance has been compared with spectral techniques of classical diffraction tomography, the modified Newton method, and the pseudo-inverse method. >