Element displacement and contact impedance changes are compensated in the reconstruction approach. Images have been reconstructed using the proposed method with the data from numerical simulation, saline phantom and in vivo human measurement

Dai, Tao

Pu, Yang

Carleton University's Institutional Repository

86 SESSION 10. RECONSTRUCTION IIReconstruction of Conductivity Changes Using an Advanced Compensation Method in Electrical Impedance Tomography Yang Pu and Tao Dai Sealand Technology (Chengdu), Ltd., Chengdu, China.  ypu@eitchina.net  Abstract: Element displacement and contact impedance changes are compensated in the reconstruction approach. Images have been reconstructed using the proposed method with the data from numerical simulation, saline phantom and in vivo human measurement. 1 Introduction One of the key difficulties of Electrical impedance tomography (EIT) imaging is the modelling error, such as shape deformation and contact impedance changes. When a deformable medium is investigated, not only boundary elements (including electrodes) but also internal elements displace. Moreover, when the voltages are measured on the electrodes, the contact impedance that exists in the interface causes a voltage drop. If difference imaging techniques are involved, these difficulties can be partly solved [1-3], but in order to obtain a better imaging quality, element displacement and contact impedance changes have to be taken into account. 2 Methods An augmented Jacobian ? ? ????????????  is obtained by concatenating conductivity change Jacobian ??? , element displacement Jacobian ?? and contact impedance changes Jacobian ??. A modified NOSER prior ?????? ? ???????????? is established, where ?? ? ????????????????, we define ? and ? as the model hyperparameters to represent the different weights. The one-step linear Gauss-Newton (GN) method is implemented to solve the inverse problem. 2.1 Numerical Simulation                      Figure 1: Image reconstructions. (a) Standard GN method; (b) Electrode movement model; (c) Proposed method with ? ? ? and ? ? ? ; (d) Proposed method with ? ? ????? and ? ? ???. From left to right, distortion amplitude increases from 0%, 1% to 3% of model diameter respectively. 2.2 Saline Phantom Measurement The saline phantom is a plastic cylindrical tank with 14cm diameter and 12cm height, being filled with 0.9% saline solution. A small non-conductive spherical object of 1cm diameter was statically suspended. The proposed method successfully obtained the inhomogeneous target without introducing any artefacts. 2.3 In vivo Human Measurement  Figure 2: Images of lung ventilation. The breathing cycle from end inspiration to end expiration was approximately 5 seconds. Each second was shown in the same row. 3 Conclusions An advanced compensation method which is more robust to shape distortion is proposed in this paper by an improved version of the electrode movement model [1]. The algorithm performed well and showed significant improvements of artefact resistance. One key advantage is that, once pre-calculations are completed, images can be reconstructed by a single regularized inverse, and it requires little additional time over traditional methods. Considering the reconstructed images from in vivo human measurement, this method shows potential to be applied in real time monitoring of lung ventilation and may be useful to increase the accuracy and reliability of EIT technique in routine clinical applications. References [1] M. Soleimani, Physiol. Meas. 27 S103-S13, 2006 [2] T. Dai, Physiol. Meas. 29 S77-S88, 2008 [3] A. Adler, Physiol. Meas. 32 823−834, 2011 0%                      1%                    3%                   (a) (b) (c) (d) Proceedingsof the15th International Conference onBiomedical Applications ofELECTRICAL IMPEDANCETOMOGRAPHYEdited by Andy Adler and Bartłomiej GrychtolApril 24-26, 2014Glen House ResortGananoque, OntarioCanadaThis document is the collection of papers accepted for presentation at the 15th International Conference onBiomedical Applications of Electrical Impedance Tomography.Each individual paper in this collection: c© 2014 by the indicated authors.Collected work: c© 2014 Andy Adler and Bartłomiej Grychtol.All rights reserved.Cover design: Bartłomiej GrychtolPhoto credit: c©1000 Islands Photo Art Inc. / Ian CoristinePrinted in CanadaISBN 978-0-7709-0577-4Systems and Computer EngineeringCarleton University, 1125 Colonel By DriveOttawa, Ontario, K1S 5B6, Canadaadler@sce.carleton.ca+1 (613) 520-2600www.eit2014.org

Reconstruction of Conductivity Changes Using an Advanced Compensation Method in Electrical Impedance Tomography

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Reconstruction of Conductivity Changes Using an Advanced Compensation Method in Electrical Impedance Tomography

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