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- Fhager, Andreas, 1976, et al.
(författare)
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Potential benefits of using a priori data in reconstruction algorithms for microwave tomography
- 2006
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Ingår i: Medicinteknikdagarna, 3-4 October 2006, Uppsala, Sweden.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Microwave tomography is rapidly developing into a promising imaging technique that could be useful in many different applications where a non-invasive detection of internal dielectric properties is required. Such a technique could for instance be useful in mammographical imaging for screening and follow up examinations of breast cancer tumours. Compared to x-ray mammography there is a potential significant benefit in using microwaves in the diagnosis of breast cancer tumours due to a significant contrast in the dielectric properties between tumour and surrounding tissue.Development of an efficient imaging reconstruction algorithm is a big challenge in the construction of an operational microwave tomograph. The algorithm has to be fast, accurate and robust. In this work results are presented showing how a priori dielectric data of the objects being reconstructed can be exploited to improve the convergence rate and the resolution of the reconstructed image. The work is based on a conjugate-gradient reconstruction algorithm and FDTD modelling of the electromagnetic wave propagation. For this work it has been modified to search for circular objects with given permittivity and conductivity. The results are promising and indicate that significantly improved reconstructions can be obtained. However to be practically viable further development of the algorithm need to be made in order to make it more robust and adaptive. Once that is made we plan to use this technique in a prototype that will be evaluated for clinical breast cancer imaging.
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- Fhager, Andreas, 1976, et al.
(författare)
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Towards a mammographic microwave imaging experiment
- 2004
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Ingår i: Proceedings of EMB 04 computational electromagnetics, methods and applications, Göteborg. ; , s. 132-136
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 9. |
- Hashemzadeh, Parham, 1976, et al.
(författare)
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Tracking Conductivity Variations in The Absence of Accurate State Evolution Models in Electrical Impedance Tomography
- 2010
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Ingår i: Proceedings of the 4th International Conference on Bioinformatics and Biomedical Engineering.
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Konferensbidrag (refereegranskat)abstract
- We present results on both linear and non-linear approaches in tracking conductivity variations in electrical impedance tomography. Throughout this study, we use both synthetic and measured data. The true system dynamics is considered as unknown and modelled as a random walk. In the linear reconstructions, the time evolution model is augmented with a Gaussian smoothness prior and results are shown using two different models for the covariance matrix of the process noise. Furthermore, we compare the reconstructions of the one step Gauss-Newton method to the Kalman filter on measured data from an adult human subject. In the non-linear study, we compare the performance of the extended Kalman filter against the particle filter on a simple test case. It is observed that the particle filter shows superior performance in tracking nonlinear/non-Gaussian conductivity variations.
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| 10. |
- Hashemzadeh, Parham, 1976, et al.
(författare)
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Analysis of 3-D shape estimation using bistatic multi-channel radar systems
- 2008
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Ingår i: SAM 2008 - 5th IEEE Sensor Array and Multichannel Signal Processing Workshop; Darmstadt; Germany; 21 July 2008 through 23 July 2008. - 9781424422418 ; , s. 463-467
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Konferensbidrag (refereegranskat)abstract
- We estimate the radius of a perfect electric conductor (PEC) half-sphere placed on a ground plane, given six bi-conical antennas that suffer from manufacturing errors. The results are complemented by an analytical model of the sensor system and the scatterer. The analytical model includes the front-end electronics in combination with the antenna radiation impedance and the radiation field function.
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