| 1. |
- Golnabi, Amir H., et al.
(författare)
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3-D Microwave Tomography Using the Soft Prior Regularization Technique: Evaluation in Anatomically Realistic MRI-Derived Numerical Breast Phantoms
- 2019
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Ingår i: IEEE Transactions on Biomedical Engineering. - 0018-9294 .- 1558-2531. ; 66:9, s. 2566-2575
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Tidskriftsartikel (refereegranskat)abstract
- Objective: Fusion of magnetic resonance imaging (MRI) breast images with microwave tomography is accomplished through a soft prior technique, which incorporates spatial information (from MRI), i. e., accurate boundary location of different regions of interest, into the regularization process of the microwave image reconstruction algorithm. Methods: Numerical experiments were completed on a set of three-dimensional (3-D) breast geometries derived from MR breast data with different parenchymal densities, as well as a simulated tumor to evaluate the performance over a range of breast shapes, sizes, and property distributions. Results: When the soft prior regularization technique was applied, both permittivity and conductivity relative root mean square error values decreased by more than 87% across all breast densities, except in two cases where the error decrease was only 55% and 78%. In addition, the incorporation of structural priors increased contrast between tumor and fibroglandular tissue by 59% in permittivity and 192% in conductivity. Conclusion: This study confirmed that the soft prior algorithm is robust in 3-D and can function successfully across a range of complex geometries and tissue property distributions. Significance: This study demonstrates that our microwave tomography is capable of recovering accurate tissue property distributions when spatial information from MRI is incorporated through soft prior regularization.
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| 2. |
- Hosseinzadegan, Samar, 1987, et al.
(författare)
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A discrete dipole approximation solver based on the COCG-FFT algorithm and its application to microwave breast imaging
- 2019
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Ingår i: International Journal of Antennas and Propagation. - : Hindawi Limited. - 1687-5869 .- 1687-5877. ; 2019
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Tidskriftsartikel (refereegranskat)abstract
- We introduce the discrete dipole approximation (DDA) for efficiently calculating the two-dimensional electric field distribution for our microwave tomographic breast imaging system. For iterative inverse problems such as microwave tomography, the forward field computation is the time limiting step. In this paper, the two-dimensional algorithm is derived and formulated such that the iterative conjugate orthogonal conjugate gradient (COCG) method can be used for efficiently solving the forward problem. We have also optimized the matrix-vector multiplication step by formulating the problem such that the nondiagonal portion of the matrix used to compute the dipole moments is block-Toeplitz. The computation costs for multiplying the block matrices times a vector can be dramatically accelerated by expanding each Toeplitz matrix to a circulant matrix for which the convolution theorem is applied for fast computation utilizing the fast Fourier transform (FFT). The results demonstrate that this formulation is accurate and efficient. In this work, the computation times for the direct solvers, the iterative solver (COCG), and the iterative solver using the fast Fourier transform (COCG-FFT) are compared with the best performance achieved using the iterative solver (COCG-FFT) in C++. Utilizing this formulation provides a computationally efficient building block for developing a low cost and fast breast imaging system to serve under-resourced populations.
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| 3. |
- Hosseinzadegan, Samar, 1987, et al.
(författare)
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Application of the discrete dipole approximation in microwave breast imaging
- 2019
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Ingår i: Proceedings of the 2019 21st International Conference on Electromagnetics in Advanced Applications, ICEAA 2019. ; , s. 0868-0868
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Konferensbidrag (refereegranskat)abstract
- In this work, we propose the two-dimensional discrete dipole approximation (2D DDA) to calculate the electric field distributions in the microwave imaging system. The motive is to develop a significantly fast reconstruction algorithm. To accomplish this, the 2D DDA on a uniform grid in the forward model zone is used, which enables computational times be significantly reduced compared to common algorithms.
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| 4. |
- Hosseinzadegan, Samar, 1987, et al.
(författare)
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Application of two-dimensional discrete dipole approximation in simulating electric field of a microwave breast imaging system
- 2019
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Ingår i: IEEE Journal of Electromagnetics, RF and Microwaves in Medicine and Biology. - 2469-7249. ; 3:2, s. 80-87
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Tidskriftsartikel (refereegranskat)abstract
- © 2016 IEEE. The 2-D electric field distribution of the microwave imaging system is numerically simulated for a simplified breast tumour model. The proposed two-dimensional discrete dipole approximation (DDA) has the potential to improve computational speed compared to other numerical methods while retaining comparable accuracy. We have modeled the field distributions in COMSOL Multiphysics as baseline results to benchmark the DDA simulations. We have also investigated the adequate sampling size and the effect of inclusion size and property contrast on solution accuracy. In this way, we can utilize the 2-D DDA as an alternative, fast, and reliable forward solver for microwave tomography. From a mathematical perspective, the derivation of the 2-D DDA and its application to microwave imaging is new and not previously implemented. The simulation results and the measurements show that the 2-D DDA is a well-grounded forward solver for the specified microwave breast imaging system.
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| 5. |
- Hosseinzadegan, Samar, 1987, et al.
(författare)
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Comparison of Two Forward Models For Electric Field of Microwave Imaging Systems
- 2017
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Ingår i: 2017 IEEE INTERNATIONAL SYMPOSIUM ON ANTENNAS AND PROPAGATION & USNC/URSI NATIONAL RADIO SCIENCE MEETING. - 1522-3965. - 9781538632840 ; 2017-January, s. 969-970
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Konferensbidrag (refereegranskat)abstract
- We propose an alternative numerical method, discrete dipole approximation (DDA), to model the two dimensional electric field of forward solution. Our observations show that discrete dipole approximation can be used as a fast and reliable numerical method on the forward solution of the microwave imaging systems. Two dimensional electric field of the microwave imaging systems has been modelled in finite element method with help of COMSOL Multiphysics as well. The numerical experiments obtained from COMSOL Multiphysics agree well with the discrete dipole approximation approach.
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| 6. |
- Hosseinzadegan, Samar, 1987, et al.
(författare)
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Discrete Dipole Approximation-Based Microwave Tomography for Fast Breast Cancer Imaging
- 2021
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Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 69:5, s. 2741-2752
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Tidskriftsartikel (refereegranskat)abstract
- This article describes a fast microwave tomography reconstruction algorithm based on the 2-D discrete dipole approximation (DDA). Synthetic data from a finite-element-based solver and experimental data from a microwave imaging system are used to reconstruct images and to validate the algorithm. The microwave measurement system consists of 16 monopole antennas immersed in a tank filled with lossy coupling liquid and a vector network analyzer. The low-profile antennas and lossy nature of the system make the DDA an ideal forward solver in image reconstructions. The results show that the algorithm can readily reconstruct a 2-D plane of a cylindrical phantom. The proposed forward solver combined with the nodal adjoint method for computing the Jacobian matrix enables the algorithm to reconstruct an image within 6 s. This implementation provides significant time savings and reduced memory requirements and is a dramatic improvement over previous implementations.
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| 7. |
- Hosseinzadegan, Samar, 1987, et al.
(författare)
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Expansion of the nodal-adjoint method for simple and efficient computation of the 2d tomographic imaging jacobian matrix
- 2021
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Ingår i: Sensors. - : MDPI AG. - 1424-8220. ; 21:3, s. 1-16
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- This paper focuses on the construction of the Jacobian matrix required in tomographic reconstruction algorithms. In microwave tomography, computing the forward solutions during the iterative reconstruction process impacts the accuracy and computational efficiency. Towards this end, we have applied the discrete dipole approximation for the forward solutions with significant time savings. However, while we have discovered that the imaging problem configuration can dramatically impact the computation time required for the forward solver, it can be equally beneficial in constructing the Jacobian matrix calculated in iterative image reconstruction algorithms. Key to this implementation, we propose to use the same simulation grid for both the forward and imaging domain discretizations for the discrete dipole approximation solutions and report in detail the theoretical aspects for this localization. In this way, the computational cost of the nodal adjoint method decreases by several orders of magnitude. Our investigations show that this expansion is a significant enhancement compared to previous implementations and results in a rapid calculation of the Jacobian matrix with a high level of accuracy. The discrete dipole approximation and the newly efficient Jacobian matrices are effectively implemented to produce quantitative images of the simplified breast phantom from the microwave imaging system.
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| 8. |
- Hosseinzadegan, Samar, 1987, et al.
(författare)
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Fast Jacobian Matrix Formulation for Microwave Tomography Applications
- 2021
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Ingår i: 15th European Conference on Antennas and Propagation, EuCAP 2021.
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Konferensbidrag (refereegranskat)abstract
- We have developed a new technique for computing the Jacobian matrix for microwave tomography systems which is orders of magnitude faster than conventional approaches. It exploits concepts from the nodal adjoint method and previous observations that rows of the matrix can be plotted over the imaging domain to produce sensitivity maps associated with specific transmit/receive antenna pairs. It also requires that the forward solutions and parameter reconstruction distributions be represented on the same grid or mesh. In this way, it computes full rows of the matrix simultaneously via a simple vector-vector multiplication of the forward solutions associated with sources broadcasting from both the designated transmit and receive antennas times a scalar constant. The time savings is substantial and is viable for both 2D and 3D applications.
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| 9. |
- Hosseinzadegan, Samar, 1987, et al.
(författare)
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Integrating the discrete dipole approximation forward solver with a microwave tomography algorithm
- 2018
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Ingår i: 2018 IEEE ANTENNAS AND PROPAGATION SOCIETY INTERNATIONAL SYMPOSIUM ON ANTENNAS AND PROPAGATION & USNC/URSI NATIONAL RADIO SCIENCE MEETING. - 1522-3965. - 9781538671023 - 9781538671023 ; , s. 2295-2296
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Konferensbidrag (refereegranskat)abstract
- The discrete dipole approximation (DDA) has been suggested as a viable alternative method for computing the forward solutions during the iterative reconstruction process used in microwave tomography. While efficient algorithms such as finite difference time domain and finite elements have been successfully used by multiple groups, the forward solution time remains the time-limiting step. The DDA has been shown to be accurate and efficient as a forward solver. However, the configuration of the imaging scenario can have a significant impact on its efficiency. We examine two possible forward solution set-ups and describe the benefits with respect to implementing the DDA.
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| 10. |
- Hosseinzadegan, Samar, 1987, et al.
(författare)
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On the electric field of microwave imaging systems using discrete dipole approximation
- 2018
-
Ingår i: 2018 IEEE Conference on Antenna Measurements and Applications, CAMA 2018. - 9781538657959
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Konferensbidrag (refereegranskat)abstract
- The two dimensional electric field for our microwave imaging system consisting of 16 low profile monopole antennas is modelled via the discrete dipole approximation (DDA). We have used two dimensional electromagnetic waves in frequency domain in COMSOL Multiphysics to assess the level of reliability of the proposed two dimensional numerical solver, the 2-D DDA. Our observations show that the DDA is mainly dependent on the applied resolution on the imaging domain while physical properties in the media also contribute to the overall error.
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