| 1. |
- Johansson, Markus, 1978, et al.
(författare)
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Comparison between Two Phase Retrieval Methods for Electromagnetic Source Modeling
- 2011
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Ingår i: Progress in Electromagnetics Research B. - 1937-6472. ; 30, s. 239-253
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Tidskriftsartikel (refereegranskat)abstract
- Phase-retrieval from measured phaseless field data is of interest for various applications including electromagnetic dosimetry, electromagnetic compatibility investigations, near-field to far-field transformations and antenna diagnostics. In this study two phaseretrieval methods are compared. The first method, the adjoint field method, employs a gradient-based optimization algorithm based on the adjoint fields. The second method, the phase angle gradient method, uses an optimization algorithm based on the phase angle gradients of a functional. The methods are tested with numerical test cases and the phase angle gradient method is found to retrieve the phase with the best accuracy. Moreover it gives results that agree well with correct phase.
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| 2. |
- Johansson, Markus, 1978, et al.
(författare)
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Electromagnetic Source Modeling using Phase Retrieval Methods
- 2011
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Ingår i: 30th URSI General Assembly and Scientific Symposium, URSIGASS 2011, Istanbul, 13-20 August 2011. - 9781424451173 ; , s. 1-2
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Konferensbidrag (refereegranskat)abstract
- Modeling of the field distributions from electromagnetic sources is of interest for various applications for example electromagnetic compatibility investigations, near-field to far-field transformations, antenna diagnostics and electromagnetic dosimetry. In order to determine whether exposure safety guidelines, such as the EU directive 2004/40/EC, are complied with, source modeling methods are important. Two methods for determining the total field, including phase information, when only field amplitudes have been measured on a set of planes in front of an electromagnetic source have been developed. The first method, the adjoint field method, is a gradient based optimization algorithm based on the adjoint fields. The second method, the phase angle gradient method, employs an optimization algorithm based on the phase angle gradients of a functional. Promising results have been obtained both for numerical test cases and for measured field.
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| 3. |
- Lui, Hoi-Shun, 1980, et al.
(författare)
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Analysis of Forward Scattering Data for Microwave Breast Imaging
- 2011
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Ingår i: Asia Pacific Microwave Conference. - 9781457720345 ; , s. 195-198
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Konferensbidrag (refereegranskat)abstract
- Microwave imaging for breast cancer detection has been of significant interest for the last two decades. Recent studies focus on solving the imaging problem using an inverse scattering approach. Success of these methods relies on the quality of the forward data such that the tumor inside the breast volume is well illuminated. In this paper, a numerical study of the forward scattering data is conducted and the potential use of full polarimetric data is investigated.
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| 4. |
- Lui, Hoi-Shun, 1980, et al.
(författare)
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Characterization and Detection of Breast Cancer using Ultra Wideband Polarimetric Electromagnetic Transients
- 2013
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Ingår i: 7th European Conference on Antennas and Propagation, EuCAP 2013, Gothenburg, Sweden, 8-12 April 2013. - 9781467321877
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Konferensbidrag (refereegranskat)abstract
- Detection and recognition of metallic targets based on Ultra Wideband electromagnetic transients have been widely studied throughout the years. Due to the complexity of the scattering phenomena, such techniques have not been widely applied for dielectric targets. In this paper, the potential of detection and characterization of dielectric target is investigated. Instead of using single co-polarized linear responses, Ultra wideband polarimetric responses are considered. Numerical example of a breast cancer detection scenario will be used to demonstrate the feasibility of using wideband polarimetric data to characterize dielectric target.
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| 5. |
- Lui, Hoi-Shun, 1980, et al.
(författare)
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Matching Medium for Biomedical Microwave Imaging
- 2016
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Ingår i: 2015 INTERNATIONAL SYMPOSIUM ON ANTENNAS AND PROPAGATION (ISAP).
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Konferensbidrag (refereegranskat)abstract
- The choice of matching medium in microwave imaging for biomedical applications is studied. A multi-layer planar human tissue is first used to investigate the amount electromagnetic wave is transmitted through the tissue model using different matching medium. This will give us further insights on wave propagation through human tissue, which assists us to determine to choice of matching medium. Image reconstruction of simplified human breast model with different matching medium using an inverse scattering algorithm will be used to verify our findings.
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| 6. |
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| 7. |
- Lui, Hoi-Shun, 1980, et al.
(författare)
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On the Forward Scattering of Microwave Breast Imaging
- 2012
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Ingår i: International Journal of Biomedical Imaging. - : Hindawi Limited. - 1687-4188 .- 1687-4196. ; 2012, s. 582037-
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Tidskriftsartikel (refereegranskat)abstract
- Microwave imaging for breast cancer detection has been of significant interest for the last two decades. Recent studies focus on solving the imaging problem using an inverse scattering approach. Efforts have mainly been focused on the development of the inverse scattering algorithms, experimental setup, antenna design and clinical trials. However, the success of microwave breast imaging also heavily relies on the quality of the forward data such that the tumor inside the breast volume is well illuminated. In this work, a numerical study of the forward scattering data is conducted. The scattering behavior of simple breast models under different polarization states and aspect angles of illumination are considered. Numerical results have demonstrated that better data contrast could be obtained when the breast volume is illuminated using cross-polarized components in linear polarization basis or the copolarized components in the circular polarization basis.
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| 8. |
- Lui, Hoi-Shun, 1980, et al.
(författare)
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Preliminary Investigations of Three-Dimensional Microwave Tomography using Different Data Sets
- 2012
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Ingår i: Proceedings of 6th European Conference on Antennas and Propagation, EuCAP 2012. Prague, 26-30 March 2012. - 9781457709180 ; , s. 2196-2200
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Konferensbidrag (refereegranskat)abstract
- Owing to the extensive amount of computing resources required for solving the non-linear microwave inverse scattering problems, previous numerical studies have mainly been focus on two-dimensional inverse scattering problem. In three-dimensional cases, the vectorial nature of electromagnetic waves has to be properly handled. In this paper, preliminary investigations of using vertical and horizontal components of the scattered near-field are considered. The forward data is first evaluated quantitatively and image reconstruction using the two different sets of data from the same scattering problem is performed.
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| 9. |
- Persson, Mikael, 1959, et al.
(författare)
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Advances in Neuro Diagnostic based on Microwave Technology, Transcranial Magnetic Stimulation and EEG source localization
- 2011
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Ingår i: Asia Pacific Microwave Conference, (APMC 2011;Melbourne, VIC; 5 - 8 December 2011). - 9780858259744 ; , s. 469-472
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Konferensbidrag (refereegranskat)abstract
- Advances in neuro diagnostics based on microwave antenna system in terms of a helmet including a set of broad band patch antennas is presented. It is shown that classification algorithms can be used to detect internal bleeding in stroke patients. Transcranial magnetic stimulation has traditionally been used for brain mapping and treatment of depression. In this paper we discuss the use of the method for neuro diagnostics with the help of integrated image guidance. Surgical therapy has become an important therapeutic alternative for some patients with medically intractable epilepsy. Electroencephalography and the associated model based diagnostics as a non-invasive diagnostic tool is also discussed.
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