scholarly journals Microwave Imaging of Human Forearms: Pilot Study and Image Enhancement

2013 ◽  
Vol 2013 ◽  
pp. 1-17 ◽  
Author(s):  
Colin Gilmore ◽  
Amer Zakaria ◽  
Stephen Pistorius ◽  
Joe LoVetri
Keyword(s):  
Adipose Tissue ◽  
Pilot Study ◽  
Image Quality ◽  
Prior Information ◽  
Microwave Imaging ◽  
Scattering Data ◽  
Source Inversion ◽  
Inversion Algorithm ◽  
Microwave Scattering ◽  
Imaging Results

We present a pilot study using a microwave tomography system in which we image the forearms of 5 adult male and female volunteers between the ages of 30 and 48. Microwave scattering data were collected at 0.8 to 1.2 GHz with 24 transmitting and receiving antennas located in a matching fluid of deionized water and table salt. Inversion of the microwave data was performed with a balanced version of the multiplicative-regularized contrast source inversion algorithm formulated using the finite-element method (FEM-CSI). T1-weighted MRI images of each volunteer’s forearm were also collected in the same plane as the microwave scattering experiment. Initial “blind” imaging results from the utilized inversion algorithm show that the image quality is dependent on the thickness of the arm’s peripheral adipose tissue layer; thicker layers of adipose tissue lead to poorer overall image quality. Due to the exible nature of the FEM-CSI algorithm used, prior information can be readily incorporated into the microwave imaging inversion process. We show that by introducing prior information into the FEM-CSI algorithm the internal anatomical features of all the arms are resolved, significantly improving the images. The prior information was estimated manually from the blind inversions using anad hocprocedure.

scholarly journals On the Use of Absorbing Metasurfaces in Microwave Imaging

2020 ◽  
Author(s):  
Ziqi Liu ◽  
Nozhan Bayat ◽  
Puyan Mojabi
Keyword(s):  
Inverse Scattering ◽  
Imaging System ◽  
Simulated Data ◽  
Antenna System ◽  
Microwave Imaging ◽  
Scattering Data ◽  
External Interference ◽  
Microwave Scattering ◽  
Advantages And Disadvantages ◽  
Background Medium

<p>Microwave imaging (MWI) systems are usually enclosed within casings, e.g., in order to contain the utilized coupling liquid or to help mount the antenna system. On the other hand, inverse scattering algorithms, which are used to process the measured microwave scattering data, often assume that the background medium of the imaging system extends to infinity (i.e., unbounded background medium assumption). Thus, they do not consider the reflections occurring at the system enclosure. For such algorithms to yield successful images, these reflections need to be minimized, e.g., via the use of a lossy coupling liquid. As an alternative to a lossy background medium which also reduces the desired signal level, this paper investigates the use of metallic-backed absorbing metasurfaces as the MWI system enclosure in order to (i) reduce these reflections, and also (ii) to shield the MWI system from external interference. Using simulated data, we then show that standard inverse scattering algorithms, employing the free-space assumption, can successfully process the data collected under the metasurface enclosure and yield acceptable permittivity images. The advantages and disadvantages of absorbing metasurface enclosure, along with the limitations of this study, will also be discussed. Finally, an absorbing metasurface is fabricated and its reflectivity is experimentally evaluated.</p>

Contrast Source Inversion Algorithm Applied in 3-D Microwave Imaging

2012 ◽  
Vol 468-471 ◽  
pp. 314-317
Author(s):  
Yu Xin Xie ◽  
Xue Jing Wang ◽  
Jing Hong Miao ◽  
Cui Juan Guo ◽  
Jiang Xiong Li ◽  
...  
Keyword(s):  
Integral Equation ◽  
Three Dimensional ◽  
Iterative Algorithms ◽  
Microwave Imaging ◽  
Controlled Environment ◽  
Source Inversion ◽  
Inversion Algorithm ◽  
3D Inversion ◽  
Contrast Source Inversion ◽  
Dielectric Target

This paper describes an nonlinear three-dimensional (3D) inversion algorithm for reconstructing a homogeneous dielectric target in an anechoic chamber in a controlled environment. The applied algorithm is a nonlinear iterative algorithms—two domain integral equation based method, namely the contrast source inversion (CSI) algorithm. The inversion results, which are presented and compared for the co-polorized data using the multi-frequency multi-bistatic measurements, verify the capability, the accuracy of the CSI algorithm for 3-D microwave imaging.

scholarly journals On the Use of Absorbing Metasurfaces in Microwave Imaging

2020 ◽  
Author(s):  
Ziqi Liu ◽  
Nozhan Bayat ◽  
Puyan Mojabi
Keyword(s):  
Inverse Scattering ◽  
Imaging System ◽  
Simulated Data ◽  
Antenna System ◽  
Microwave Imaging ◽  
Scattering Data ◽  
External Interference ◽  
Microwave Scattering ◽  
Advantages And Disadvantages ◽  
Background Medium

<p>Microwave imaging (MWI) systems are usually enclosed within casings, e.g., in order to contain the utilized coupling liquid or to help mount the antenna system. On the other hand, inverse scattering algorithms, which are used to process the measured microwave scattering data, often assume that the background medium of the imaging system extends to infinity (i.e., unbounded background medium assumption). Thus, they do not consider the reflections occurring at the system enclosure. For such algorithms to yield successful images, these reflections need to be minimized, e.g., via the use of a lossy coupling liquid. As an alternative to a lossy background medium which also reduces the desired signal level, this paper investigates the use of metallic-backed absorbing metasurfaces as the MWI system enclosure in order to (i) reduce these reflections, and also (ii) to shield the MWI system from external interference. Using simulated data, we then show that standard inverse scattering algorithms, employing the free-space assumption, can successfully process the data collected under the metasurface enclosure and yield acceptable permittivity images. The advantages and disadvantages of absorbing metasurface enclosure, along with the limitations of this study, will also be discussed. Finally, an absorbing metasurface is fabricated and its reflectivity is experimentally evaluated.</p>

scholarly journals Feasibility of Total Variation Noise Reduction Algorithm According to Various MR-Based PET Images in a Simultaneous PET/MR System: A Phantom Study

Diagnostics ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 319
Author(s):  
Chan-Rok Park ◽  
Seong-Hyeon Kang ◽  
Young-Jin Lee
Keyword(s):  
Image Quality ◽  
Noise Reduction ◽  
Total Variation ◽  
Parallel Imaging ◽  
Pulse Sequence ◽  
Reduction Algorithm ◽  
Median Filters ◽  
Reduction Techniques ◽  
Imaging Results ◽  
Noise Reduction Algorithm

Recently, the total variation (TV) algorithm has been used for noise reduction distribution in degraded nuclear medicine images. To acquire positron emission tomography (PET) to correct the attenuation region in the PET/magnetic resonance (MR) system, the MR Dixon pulse sequence, which is based on controlled aliasing in parallel imaging, results from higher acceleration (CAIPI; MR-ACDixon-CAIPI) and generalized autocalibrating partially parallel acquisition (GRAPPA; MR-ACDixon-GRAPPA) algorithms are used. Therefore, this study aimed to evaluate the image performance of the TV noise reduction algorithm for PET/MR images using the Jaszczak phantom by injecting 18F radioisotopes with PET/MR, which is called mMR (Siemens, Germany), compared with conventional noise-reduction techniques such as Wiener and median filters. The contrast-to-noise (CNR) and coefficient of variation (COV) were used for quantitative analysis. Based on the results, PET images with the TV algorithm were improved by approximately 7.6% for CNR and decreased by approximately 20.0% for COV compared with conventional noise-reduction techniques. In particular, the image quality for the MR-ACDixon-CAIPI PET image was better than that of the MR-ACDixon-GRAPPA PET image. In conclusion, the TV noise-reduction algorithm is efficient for improving the PET image quality in PET/MR systems.

Integrating prior information into microwave tomography Part 1: Impact of detail on image quality

2017 ◽  
Vol 44 (12) ◽  
pp. 6461-6481 ◽  
Author(s):  
Douglas Kurrant ◽  
Anastasia Baran ◽  
Joe LoVetri ◽  
Elise Fear
Keyword(s):  
Image Quality ◽  
Prior Information ◽  
Microwave Tomography

Finite-element contrast source inversion method for microwave imaging

2010 ◽  
Vol 26 (11) ◽  
pp. 115010 ◽  
Author(s):  
Amer Zakaria ◽  
Colin Gilmore ◽  
Joe LoVetri
Keyword(s):  
Finite Element ◽  
Microwave Imaging ◽  
Inversion Method ◽  
Source Inversion ◽  
Contrast Source Inversion

scholarly journals Phaseless Imaging by Reverse Time Migration: Acoustic Waves

2017 ◽  
Vol 10 (1) ◽  
pp. 1-21 ◽  
Author(s):  
Zhiming Chen ◽  
Guanghui Huang
Keyword(s):  
Acoustic Waves ◽  
Numerical Experiments ◽  
Cross Correlation ◽  
Scattering Data ◽  
Imaging Method ◽  
Total Field ◽  
Reverse Time ◽  
Reverse Time Migration ◽  
Time Migration ◽  
Imaging Results

AbstractWe propose a reliable direct imaging method based on the reverse time migration for finding extended obstacles with phaseless total field data. We prove that the imaging resolution of the method is essentially the same as the imaging results using the scattering data with full phase information when the measurement is far away from the obstacle. The imaginary part of the cross-correlation imaging functional always peaks on the boundary of the obstacle. Numerical experiments are included to illustrate the powerful imaging quality

scholarly journals Multiple-Penalty-Weighted Regularization Inversion for Dynamic Light Scattering

2018 ◽  
Vol 8 (9) ◽  
pp. 1674
Author(s):  
Wengang Chen ◽  
Wenzheng Xiu ◽  
Jin Shen ◽  
Wenwen Zhang ◽  
Min Xu ◽  
...  
Keyword(s):  
Particle Size ◽  
Light Scattering ◽  
Dynamic Light Scattering ◽  
Simulated Data ◽  
Bimodal Distribution ◽  
Scattering Data ◽  
Inversion Algorithm ◽  
Penalty Term ◽  
Peak Resolution ◽  
Time Period

By using different weights to deal with the autocorrelation function data of every delay time period, the information utilization of dynamic light scattering can be obviously enhanced in the information-weighted constrained regularization inversion, but the denoising ability and the peak resolution under noise conditions for information-weighted inversion algorithm are still insufficient. On the basis of information weighting, we added a penalty term with the function of flatness constraints to the objective function of the regularization inversion, and performed the inversion of multiangle dynamic light scattering data, including the simulated data of bimodal distribution particles (466/915 nm, 316/470 nm) and trimodal distribution particles (324/601/871 nm), and the measured data of bimodal distribution particles (306/974 nm, 300/502 nm). The results of the inversion show that multiple-penalty-weighted regularization inversion can not only improve the utilization of the particle size information, but also effectively eliminate the false peaks and burrs in the inversed particle size distributions, and further improve the resolution of peaks in the noise conditions, and then improve the weighting effects of the information-weighted inversion.

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