Anatomically constrained electrical impedance tomography for three-dimensional anisotropic bodies

Glidewell, M.E.; Ng, K.T.

doi:10.1109/42.640746

Cited by 29 publications

(24 citation statements)

References 12 publications

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“…Based on these findings, we conclude that an external procedure of estimating the skull conductivity is needed. This can be accomplished through EIT (Salman et al 2005, Tidswell et al 2001, Glidewell and Ng 1997. Since the uncertainty is not completely eliminated even with separate measurement setups, the estimate obtained in such a method should be used as a mean value of the prior of the probabilistic model with some assumed form of the distribution.…”

Section: Discussionmentioning

confidence: 99%

“…Extracting information about skull conductivity from the data concurrently with dipole parameters impairs the accuracy of the result. It is essential to obtain the skull conductivity in a separate procedure (Salman et al 2005, Tidswell et al 2001, Glidewell and Ng 1997 lest the accuracy deteriorates considerably. However, existing conductivity measurements do not eliminate all the uncertainties.…”

Section: Probabilistic Forward Modelmentioning

confidence: 99%

“…However, these surface based measurements suffer from much of the ill-posed character associated with the inverse problem of source localization. While general tomographic reconstruction is limited in performance and accuracy, several investigators have reported good results by constraining the geometry of the various classes of tissue based on medical image data, and fitting a small number of class impedance values based on EIT data (Glidewell andNg 1997, Salman et al 2005). However, the highly resistive skull limits most of the current to the superficial layers or the head (e.g.…”

Section: Introductionmentioning

confidence: 99%

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Probabilistic forward model for electroencephalography source analysis

Plis¹,

George²,

Jun³

et al. 2007

Phys. Med. Biol.

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Source localization by electroencephalography (EEG) requires an accurate model of head geometry and tissue conductivity. The estimation of source time courses from EEG or from EEG in conjunction with magnetoencephalography (MEG) requires a forward model consistent with true activity for the best outcome. Although MRI provides an excellent description of soft tissue anatomy, a high resolution model of the skull (the dominant resistive component of the head) requires CT, which is not justified for routine physiological studies. Although a number of techniques have been employed to estimate tissue conductivity, no present techniques provide the noninvasive 3D tomographic mapping of conductivity that would be desirable. We introduce a formalism for probabilistic forward modeling that allows the propagation of uncertainties in model parameters into possible errors in source localization. We consider uncertainties in the conductivity profile of the skull, but the approach is general and can be extended to other kinds of uncertainties in the forward model. We and others have previously suggested the possibility of extracting conductivity of the skull from measured electroencephalography data by simultaneously optimizing over dipole parameters and the conductivity values required by the forward model. Using Cramer-Rao bounds, we demonstrate that this approach does not improve localization results nor does it produce reliable conductivity estimates. We conclude that the conductivity of the skull has to be either accurately measured by an independent technique, or that the uncertainties in the conductivity values should be reflected in uncertainty in the source location estimates.

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Section: Discussionmentioning

confidence: 99%

Section: Probabilistic Forward Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Probabilistic forward model for electroencephalography source analysis

Plis¹,

George²,

Jun³

et al. 2007

Phys. Med. Biol.

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“…different electrical conductivity values are assigned for axial, s L and transverse direction, s T , of the fibre; table 1) in accordance with the previous studies on anisotropic tissue conductivity [16][17][18][19][20][21][22][23][24][25]. According to the muscle fibre orientations on the planes, the conductivity tensor can be transformed as follows, similar to the previous study [28]:…”

Section: Electrical Conductivity Modelmentioning

confidence: 77%

Impact of surrounding tissue on conductance measurement of coronary and peripheral lumen area

Choi

Jansen

Zhang

et al. 2012

J. R. Soc. Interface.

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Parallel conductance (electric current flow through surrounding tissue) is an important determinant of accurate measurements of arterial lumen diameter, using the conductance method. The present study is focused on the role of non-uniform geometrical/electrical configurations of surrounding tissue, which are a primary source of electric current leakage. Computational models were constructed to simulate the conductance catheter measurement with two different excitation electrodes spacings (i.e. 12 and 20 mm for coronary and peripheral sizing, respectively) for different vessel -tissue configurations: (i) blood vessel fully embedded in muscle tissue, (ii) blood vessel superficially embedded in muscle tissue, and (iii) blood vessel superficially embedded in muscle tissue with fat covering half of the arterial vessel (anterior portion). The simulations suggest that the parallel conductance and accuracy of measurement is dependent on the inhomogeneous/anisotropic configuration of surrounding tissue, including the asymmetric dimension and anisotropy in electrical conductivity of surrounding tissue. Specifically, the measurement was shown to be accurate as long as the vessel was superficial, regardless of the considerable total surrounding tissue dimension for coronary or peripheral arteries. Moreover, it was shown that the unfavourable impact of parallel conductance on the accuracy of conductance catheter measurement is decreased by the combination of a lower transverse electrical conductivity of surrounding muscle tissue, a smaller electrode spacing and a larger lumen diameter. The present findings confirm that the conductance catheter technique provides an accurate platform for sizing of clinically relevant (i.e. superficial and diseased) arteries.

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“…Numerical reconstructions of anisotropic conductivity in a geophysical context include [116], although there the problem of non-uniqueness of solution (diffeomorphism invariance) has been ignored. Another approach is to assume piece-wise constant conductivity with the discontinuities know, for example from an MRI image, and seek to recover the constant anisotropic conductivity in each region [56], [57].…”

Section: Direct Non-linear Methodsmentioning

confidence: 99%