Real-Time Imaging With Simultaneous Use of Born and Rytov Approximations in Quantitative Microwave Holography

Abstract

Microwave and millimeter-wave measurements acquire total-field responses from measurements, yet imaging algorithms instead require the data in the form of scatteredfield responses. Two approaches exist for the extraction of the scattered-field data from the total-field responses, namely, the Born and the Rytov data approximations. It is well known that, depending on the target's size, contrast, and structural complexity, one approximation can achieve an improved accuracy over the other. Yet, the Rytov approximation is rarely used in microwave and millimeter-wave imaging, likely due to phaseunwrapping problems occurring in the case of strongly heterogeneous electrically large targets. Here, we propose a method to utilize the Born and the Rytov approximations simultaneously in a single inversion step for real-time imaging with quantitative microwave holography (QMH). We show through examples with simulated and experimental data that in near-field imaging scenarios, including the imaging of a breast-tissue phantom, there are significant benefits in employing the new method.

Accurate Range Migration for Fast Quantitative Fourier-Based Image Reconstruction With Monostatic Radar

“…Finally, the limitations with regard to the imaging of electrically large high-contrast targets must be kept in mind. Such targets violate the Born and Rytov approximations that are the basis of the scattered-field data extraction strategies employed by many direct reconstruction algorithms [9], [39]. Additionally, the linearized model of scattering employed by such algorithms does not account for higher-order scattering effects such as multiple scattering and mutual coupling, which can be significant in the presence of large high-contrast objects.…”

“…Also, the efficacy of the proposed method is to be further validated with other quantitative Fourier-based imaging algorithms, e.g., [30]. APPENDIX QUANTITATIVE MICROWAVE HOLOGRAPHY QMH has been extensively derived in previous publications and is only briefly described here for contextual purposes [9], [10], [32].…”

“…The proposed range-migration approach is applicable not only with the conventional qualitative Fourier-based image reconstruction. Recently, Fourier-based quantitative imagereconstruction methods have been proposed [9], [29]- [31]. The quantitative estimation of the dielectric profile of an OUT becomes possible with the use of measured system point-spread functions (PSFs) in place of analytical/simulated resolvent kernels.…”

“…We also highlight the limitations of the method related to the initial PSF measurement position and give recommendations for Fourier-domain filtering based on the maximum viewing angle at the refocused SP range location. The method is validated with both simulated and experimental data used in image reconstruction with quantitative microwave holography (QMH) [9], [29], [32].…”

Experimental Assessment of Real-Time Brain Stroke Monitoring via a Microwave Imaging Scanner

“…Furthermore, [15]- [17] present real-time MWI applied to other medical issues. [15] integrates Born and Rytov linear approximations with quantitative microwave holography, allowing leverage of their advantages depending on the object's geometry and contrast. It experimentally tests the technique in a simplified breast imaging case.…”