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Measurement System for Microwave Imaging Towards a Biomedical Application
Mälardalen University, School of Innovation, Design and Engineering. Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems. (IFT)ORCID iD: 0000-0002-2457-3079
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Microwave imaging techniques have shown excellent capabilities in various fields such as civil engineering, nondestructive testing, industrial applications, and have in recent decades experienced strong growth as a research topic in biomedical diagnostics. Many research groups throughout the world work on prototype systems for producing images of human tissues in different biomedical applications, particularly breast tumor detection. However, the research community faces many challenges and in order to be competitive to other imaging modalities one of the means is to put emphasis on experimental work. Consequently, the use of flexible and accurate measurement systems, together with the design and fabrication of suitable antennas, are essential to the development of efficient microwave imaging systems.

The first part of this thesis focuses on measurement systems for microwave imaging in terms of antenna design and development, robot controlled synthetic array geometries, permittivity measurements, and calibration. The aim was to investigate the feasibility of a flexible system for measuring the fields around an inhomogeneous object and to create quantitative images. Hence, such an aim requires solving of a nonlinear inverse scattering problem, which in turn requires accurate measurements for producing good quality experimental data. The presented solution by design of a flexible measurement system is validated by examination of microwave imaging from experimental data with a breast phantom.

The second part of the thesis deals with the research challenges of designing high performance antennas to be placed in direct contact with or in close proximity to the imaged object. The need for novel antenna applicators is envisaged in the framework of the Mamacell measurement system, where the antenna applicators have to be designed and constructed to effectively couple the energy into the imaging object. For this purpose the main constraints and design requirements are a narrow lobe of the antenna, very small near-field effects, and small size. Numerical simulations and modeling shows that the proposed ridged waveguide antenna is capable of fulfilling the design requirements and the performance goals, demonstrating the potential for the future microwave imaging system called Mamacell.

Place, publisher, year, edition, pages
Västerås: Mälardalen University , 2014.
Series
Mälardalen University Press Dissertations, ISSN 1651-4238 ; 157
Keyword [en]
Microwave imaging, antenna applicator, data acquisition, nonlinear inverse scattering
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electronics
Identifiers
URN: urn:nbn:se:mdh:diva-24878ISBN: 978-91-7485-146-5 (print)OAI: oai:DiVA.org:mdh-24878DiVA: diva2:713609
Public defence
2014-05-28, Paros, Mälardalens högskola, Västerås, 10:00 (English)
Opponent
Supervisors
Available from: 2014-04-23 Created: 2014-04-23 Last updated: 2015-02-04Bibliographically approved
List of papers
1. Permittivity Measurements with a Resonant Cavity to Develop Human Tissue Phantoms for Microwave Imaging
Open this publication in new window or tab >>Permittivity Measurements with a Resonant Cavity to Develop Human Tissue Phantoms for Microwave Imaging
2009 (English)In: Proceedings of the 8th International Conference on Electromagnetic Wave Interaction with Water and Moist Substances (ISEMA 2009) / [ed] Pertti Vainikainen, Helsinki, 2009, 190-195 p.Conference paper, Published paper (Refereed)
Abstract [en]

In order to create human tissue phantoms for a microwave imaging system, a method to determine the complex permittivity is needed. For this reason a cavity perturbation method has been analyzed and used to perform measurements characterizing the complex permittivity of different fluid mixtures. Results show good agreement on single frequency between the measurement with the reentrant cavity and references. However the complex part of the final material mixture mimicking human tissue are higher than expected, which makes 1.2-propylene glycol inappropriate as a human tissue phantom material. The cavity perturbation method is still a suitable method for measuring liquids and with more work it might even be reliable for gel-based materials.

Place, publisher, year, edition, pages
Helsinki: , 2009
National Category
Engineering and Technology
Identifiers
urn:nbn:se:mdh:diva-8946 (URN)978-951-22-9940-9 (ISBN)
Conference
8th International Conference on Electromagnetic Wave Interaction with Water and Moist Substances (ISEMA 2009),June 1-5, 2009, Espoo, Finland
Available from: 2010-03-03 Created: 2010-03-03 Last updated: 2014-12-08Bibliographically approved
2. Antenna Modeling Issues in Quantitative Image Reconstruction Using a Flexible Microwave Tomography System
Open this publication in new window or tab >>Antenna Modeling Issues in Quantitative Image Reconstruction Using a Flexible Microwave Tomography System
2010 (English)In: PIERS 2010 CAMBRIDGE: PROGRESS IN ELECTROMAGNETICS RESEARCH SYMPOSIUM PROCEEDINGS, 2010, 952-956 p.Conference paper, Published paper (Refereed)
Abstract [en]

Quantitative microwave imaging has been extensively studied in the past years as an alternative technique in biomedical imaging, with a strong potential in early stage breast can- cer detection [Keith D. Paulsen and Paul M. Meaney, \Alternative Breast Imaging", The Springer International Series in Engineering and Computer Science, 778, 2005]. The image reconstruction involves a nonlinear inverse scattering problem, which consists to retrieve the dielectric prop- erties of the biological object from the measured scattered field, for an applied incident field. Consequently, the solution is highly sensitive to model errors in the incident field. This paper focus on the impact of this model error on the reconstructed quantitative image using a °exible robotic microwave imaging system, developed at MAalardalen University, together with an itera- tive Newton-Kantorovich (NK) algorithm. This study is conducted during the development of the imaging system and the first quantitative images of a breast phantom are obtained. The robotic microwave imaging system is developed as a °exible experimental platform for biomedical imaging, where one of the applications is breast imaging. Using a robot controlled system the scattered field can be measured with a single transmitting/receiving antenna-pair, thus avoiding the mutual coupling that occur when an antenna-array is used. The scattered field is, herein, measured around a breast phantom, along a circular arc, in the horizontal plane with vertically polarized monopole antennas, considering a two dimensional transverse magnetic case (2D-TM). The radiated field from the transmitting antenna is modeled as a vertical polarized cylindrical wave in the numerical incident field model of the NK algorithm, where images with both the real- and imaginary permittivity profile of the breast phantom are obtained. In this study, two di®erent monopole antenna designs are compared with the numerical incident field model. The di®erence between the antennas is the ground-plane design, where the first setup uses 4 wires forming a horizontal cross as a ground-plane. By varying the length of the wires and angel between the transmitting and receiving antenna the incident electromagnetic field is changed and could be modified to best fit the simulated field. The second setup uses a circular ground plane which will give a more rotational symmetric radiation pattern in the horizontal plane and a better match when comparing measured fields with computed values. The comparison is done directly with the numerical incident field model, as well as the computed and measured scattered field, and finally the impact on the reconstructed images by the NK algorithm are compared, using measured data from both antennas. The results show how the antenna selection impacts the error between the measured incident field and the numerical model, and how the quantitative image of an inhomogeneous object is a®ected by this model error.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:mdh:diva-10902 (URN)000305490800203 ()978-1-934142-14-1 (ISBN)
Conference
Progress in Electromagnetics Research Symposium Location: Cambridge, MA Date: JUL 05-08, 2010
Available from: 2010-11-10 Created: 2010-11-10 Last updated: 2014-12-08Bibliographically approved
3. Robot Controlled Data Acquisition System for Microwave Imaging
Open this publication in new window or tab >>Robot Controlled Data Acquisition System for Microwave Imaging
2009 (English)In: 3rd European Conference on Antennas and Propagation, 2009, , 5 p.3240-3244 p.Conference paper, Published paper (Refereed)
Abstract [en]

In this paper an experimental prototype of a robot controlled data acquisition system for microwave imaging is presented, where the transmitting and receiving antennas are immersed in a water-tank. The scattered field from the object under test is acquired by using the robot and scanning a single receiving antenna in cylindrical or half spherical coordinates, while the transmitting antenna is fixed at one position with possibilities to be manually moved to different positions. Careful design and construction of the system has given accurate measurements of incident and total field with a SNR of 45dB. A validation of the robot system is performed by comparing measured and computed data for a sunflower oil object.In this paper an experimental prototype of a robot controlled data acquisition system for microwave imaging is presented, where the transmitting and receiving antennas are immersed in a water-tank. The scattered field from the object under test is acquired by using the robot and scanning a single receiving antenna in cylindrical or half spherical coordinates, while the transmitting antenna is fixed at one position with possibilities to be manually moved to different positions. Careful design and construction of the system has given accurate measurements of incident and total field with a SNR of 45dB. A validation of the robot system is performed by comparing measured and computed data for a sunflower oil object.

Publisher
5 p.
Keyword
Microwave Imaging, data acquisition, experimental data, monopole antenna, system validation
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electronics
Identifiers
urn:nbn:se:mdh:diva-5895 (URN)000276522101309 ()978-1-4244-4753-4 (ISBN)
Conference
3rd European Conference on Antennas and Propagation Location: Berlin, GERMANY Date: MAR 23-27, 2009
Projects
Microwaves in biomedicine
Available from: 2009-05-14 Created: 2009-05-14 Last updated: 2014-12-08Bibliographically approved

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