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| 2. |
- Fhager, Andreas, et al.
(författare)
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Image Reconstruction in Microwave Tomography Using a Dielectric Debye Model
- 2012
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Ingår i: IEEE Transactions on Biomedical Engineering. - 0018-9294. ; 59:1, s. 156-166
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, quantitative dielectric image reconstruction based on broadband microwave measurements is investigated. A time-domain-based algorithm is derived where Debye model parameters are reconstructed in order to take into account the strong dispersive behavior found in biological tissue. The algorithm is tested with experimental and numerical data in order to verify the algorithm and to investigate improvements in the reconstructed image resulting from the improved description of the dielectric properties of the tissue when using broadband data. The comparison is made in relation to the more commonly used conductivity model. For the evaluation, two examples were considered, the first was a lossy saline solution and the second was less lossy tap water. Both liquids are strongly dispersive and used as a background medium in the imaging examples. The results show that the Debye model algorithm is of most importance in the tap water for a bandwidth of more than 1.5 GHz. Also the saline solution exhibits a dispersive behavior but since the losses restrict the useful bandwidth, the Debye model is of less significance even if somewhat larger and stronger artifacts can be seen in the conductivity model reconstructions
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| 3. |
- Nordebo, Sven, et al.
(författare)
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An adjoint field approach to Fisher information-based sensitivity analysis in electrical impedance tomography
- 2010
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Ingår i: Inverse Problems. - 0266-5611. ; 26:12
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Tidskriftsartikel (refereegranskat)abstract
- An adjoint field approach is used to formulate a general numerical framework for Fisher information-based sensitivity analysis in electrical impedance tomography. General expressions are given for the gradients used in standard least-squares optimization, i.e. the Jacobian related to the forward problem, and it is shown that these gradient expressions are compatible with commonly used electrode models such as the shunt model and the complete electrode model. By using the adjoint field formulations together with a variational analysis, it is also shown how the computation of the Fisher information can be integrated with the gradient calculations used for optimization. It is furthermore described how the Fisher information analysis and the related sensitivity map can be used in a preconditioning strategy to obtain a well-balanced parameter sensitivity and improved performance for gradient-based quasi-Newton optimization algorithms in electrical impedance tomography. Numerical simulations as well as reconstructions based on experimental data are used to illustrate the sensitivity analysis and the performance of the improved inversion algorithm in a four-electrode measurement set-up.
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| 4. |
- Nordebo, Sven, et al.
(författare)
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Fisher Information Analysis in Microwave Tomography
- 2009
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Ingår i: Proceedings of The Third International Workshop on Computational Advances in Multi-Sensor Adaptive Processing(CAMSAP2009), Dec 13-16 2009, Aruba, Dutch Antilles. - 978-1-4244-5180-7
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Konferensbidrag (refereegranskat)
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