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K G Boone

Bio: K G Boone is an academic researcher from University College London. The author has contributed to research in topics: Electrical impedance tomography & Electrical impedance. The author has an hindex of 8, co-authored 8 publications receiving 2318 citations.

Papers
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Journal ArticleDOI
TL;DR: It is concluded that the patient's skin should be abraded to reduce impedance, and measurements should be avoided in the first 10 min after electrode placement, to allow satisfactory images.
Abstract: A computer simulation is used to investigate the relationship between skin impedance and image artefacts in electrical impedance tomography. Sets of electrode impedance are generated with a pseudo-random distribution and used to introduce errors in boundary voltage measurements. To simplify the analysis, the non-idealities in the current injection circuit are replaced by a fixed common-mode error term. The boundary voltages are reconstructed into images and inspected. Where the simulated skin impedance remains constant between measurements, large impedances (> 2k omega) do not cause significant degradation of the image. Where the skin impedances 'drift' between measurements, a drift of 5% from a starting impedance of 100 omega is sufficient to cause significant image distortion. If the skin impedances vary randomly between measurements, they have to be less than 10 omega to allow satisfactory images. Skin impedances are typically 100-200 omega at 50 kHz on unprepared skin. These values are sufficient to cause image distortion if they drift over time. It is concluded that the patient's skin should be abraded to reduce impedance, and measurements should be avoided in the first 10 min after electrode placement.

1,976 citations

Patent
19 Dec 1997
TL;DR: In this paper, a method and apparatus for use in imaging a body using electrical impedance tomography (EIT) is described, where a plurality of electrodes are provided in electrical contact with the body around the periphery of the body and the resulting electrical output signal is measured at one or more pairs of the remaining electrodes over the first and second time periods.
Abstract: A method and apparatus for use in imaging a body uses electrical impedance tomography (EIT). A plurality of electrodes are provided in electrical contact with the body around the periphery of the body. A first electrical input signal is applied to at least one of the electrodes over a first time period, and a second electrical input signal, which is preferably in inverted form of the first, then applied to the at least one of the electrodes over a subsequent, second time period. The resulting electrical output signal is measured at one or more pairs of the remaining electrodes over the first and second time periods and the difference between the measured signal obtained during the first time period and that obtained during the second time period is calculated to provide a difference signal. The difference signal can stored and used for image reconstruction. The invention has particular application in imaging neurological function within the body, where the impedance changes associated with neuronal depolarizations are very small and the resulting electrical signals measured at the body periphery are even smaller. By use of this technique electrical signals corresponding to the dynamic components of impedance change can be reinforced whilst those corresponding to other unwanted components can be cancelled.

115 citations

Journal ArticleDOI
TL;DR: There are formidable instrumentation problems, due to the interaction of finite current drive output impedance, recording amplifier common mode rejection, and unequal skin-electrode impedances.
Abstract: Electrical impedance tomography (EIT) is a novel medical imaging method, which allows reconstructed tomographic images of the internal impedance of a subject to be made with the use of a ring of electrodes. High precision impedance measurements are needed, because the image reconstruction process is ill-conditioned and small errors in measurement can lead to large errors in the final image. In practice, there are formidable instrumentation problems, due to the interaction of finite current drive output impedance, recording amplifier common mode rejection, and unequal skin - electrode impedances. A number of different EIT systems have been constructed or are under development. These employ differing strategies, such as additional electrodes, multiple electrode current injection, or recording at multiple frequencies, to improve image accuracy. This paper reviews the nature of the instrumentation problems and the designs employed by differing groups in attempting to overcome them.

105 citations

Journal ArticleDOI
TL;DR: The purpose of these experiments was to determine whether EIT could be used to localize the origin of seizure activity and results are sufficiently encouraging that it is intended to extend this study to human patients.
Abstract: Severe epileptics may require curative neurosurgery. Sometimes focus localization requires recording with electrodes inserted deep into the brain, which may cause death or permanent neurological damage. Since epileptic seizures are associated with marked changes in cerebral impedance, we propose that EIT with sub-dural electrodes (inserted between the brain and skull) could provide a superior and less dangerous method for the localization of epileptic foci. The purpose of these experiments was to determine whether EIT could be used to localize the origin of seizure activity. In terms of impedance characteristics, an appropriate model is cortical spreading depression in the animal brain. Six rabbits were anaesthetized and paralysed and the brain exposed. EIT images and DC potentials were recorded from an array of 16 electrodes on the brain during cortical spreading depression induced by DC stimulus. Cortical spreading depression could be localized by EIT with an accuracy of 8.7% +/- 6.4% (mean +/- SD) of electrode array diameter. The errors in localization appeared to be distributed randomly. In a phantom of similar geometry, the error was 5% after correction for a systematic component. Results are sufficiently encouraging that we intend to extend this study to human patients.

63 citations

Journal ArticleDOI
TL;DR: A novel algorithm for the reconstruction of dynamic images using diametric excitation has been developed, specifically designed to image impedance changes in the brain using boundary data obtained from scalp electrodes by incorporating a priori information.
Abstract: A novel algorithm for the reconstruction of dynamic images using diametric excitation has been developed. The algorithm is specifically designed to image impedance changes in the brain using boundary data obtained from scalp electrodes by incorporating a priori information. The a priori information is obtain by solving the forward problem using a finite-element model (FEM) which includes the discontinuity of the skull resistivity. The advantages with this new approach are that the sensitivity and accuracy of the location of the impedance changes are improved compared to methods based on adjacent excitation.

51 citations


Cited by
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Journal ArticleDOI
TL;DR: A survey of the work in electrical impedance tomography can be found in this article, where the authors survey some of the most important works in the field. Butt.t.
Abstract: t. This paper surveys some of the work our group has done in electrical impedance tomography.

1,726 citations

Journal ArticleDOI
TL;DR: This paper reviews ultrasound segmentation methods, in a broad sense, focusing on techniques developed for medical B-mode ultrasound images, and presents a classification of methodology in terms of use of prior information.
Abstract: This paper reviews ultrasound segmentation methods, in a broad sense, focusing on techniques developed for medical B-mode ultrasound images. First, we present a review of articles by clinical application to highlight the approaches that have been investigated and degree of validation that has been done in different clinical domains. Then, we present a classification of methodology in terms of use of prior information. We conclude by selecting ten papers which have presented original ideas that have demonstrated particular clinical usefulness or potential specific to the ultrasound segmentation problem

1,150 citations

PatentDOI
TL;DR: In this paper, a new method for the ablation of undesirable tissue such as cells of a cancerous or non-cancerous tumor is disclosed, which involves the placement of electrodes into or near the vicinity of the undesirable tissue through the application of electrical pulses causing irreversible electroporation of the cells throughout the entire area of the desired tissue.
Abstract: A new method for the ablation of undesirable tissue such as cells of a cancerous or non-cancerous tumor is disclosed. It involves the placement of electrodes into or near the vicinity of the undesirable tissue through the application of electrical pulses causing irreversible electroporation of the cells throughout the entire area of the undesirable tissue. The electric pulses irreversibly permeate the cell membranes, thereby invoking cell death. The irreversibly permeabilized cells are left in situ and are removed by the body immune system. The amount of tissue ablation achievable through the use of irreversible electroporation without inducing thermal damage is considerable.

1,137 citations

Journal ArticleDOI
TL;DR: Results show that CAP can efficiently separate several steatosis grades and suggest that CAP is a noninvasive, immediate, objective and efficient method to detect and quantify Steatosis.
Abstract: There is a need for noninvasive methods to detect liver steatosis, which can be a factor of liver fibrosis progression. This work aims to evaluate a novel ultrasonic controlled attenuation parameter (CAP) devised to target, specifically, liver steatosis using a sophisticated process based on vibration control transient elastography (VCTE™). CAP was first validated as an estimate of ultrasonic attenuation at 3.5 MHz using Field II simulations and tissue-mimicking phantoms. Performance of the CAP was then appraised on 115 patients, taking the histological grade of steatosis as reference. CAP was significantly correlated to steatosis (Spearman ρ = 0.81, p < 10(-16)). Area under receiver operative characteristic (ROC) curve (AUC) was equal to 0.91 and 0.95 for the detection of more than 10% and 33% of steatosis, respectively. Furthermore, results show that CAP can efficiently separate several steatosis grades. These promising results suggest that CAP is a noninvasive, immediate, objective and efficient method to detect and quantify steatosis.

679 citations

Journal ArticleDOI
TL;DR: Results on real images demonstrate that the proposed adaptation of the nonlocal (NL)-means filter for speckle reduction in ultrasound (US) images is able to preserve accurately edges and structural details of the image.
Abstract: In image processing, restoration is expected to improve the qualitative inspection of the image and the performance of quantitative image analysis techniques. In this paper, an adaptation of the nonlocal (NL)-means filter is proposed for speckle reduction in ultrasound (US) images. Originally developed for additive white Gaussian noise, we propose to use a Bayesian framework to derive a NL-means filter adapted to a relevant ultrasound noise model. Quantitative results on synthetic data show the performances of the proposed method compared to well-established and state-of-the-art methods. Results on real images demonstrate that the proposed method is able to preserve accurately edges and structural details of the image.

547 citations