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David Holder

Bio: David Holder is an academic researcher from University College London. The author has contributed to research in topics: Electrical impedance tomography & Iterative reconstruction. The author has an hindex of 44, co-authored 230 publications receiving 8001 citations. Previous affiliations of David Holder include General Electric & University of Cape Town.


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

BookDOI
31 Dec 2004
TL;DR: This chapter discusses Imaging of the Thorax by EIT EIT of Brain Function Breast Cancer Screening with EIT applications of EIT in the Gastrointestinal Tract (GIT) Other Clinical Applications of Eit.
Abstract: INTRODUCTION PART 1 ALGORITHMS The Reconstruction Problem PART 2 HARDWARE EIT Instrumentation PART 3 APPLICATIONS Imaging of the Thorax by EIT EIT of Brain Function Breast Cancer Screening with EIT Applications of EIT in the Gastrointestinal Tract (GIT) Other Clinical Applications of EIT PART 4 NEW DIRECTIONS Magnetic Induction Tomography Magnetic Resonance Electrical Impedance Tomography (MREIT) Electrical Tomography for Industrial Applications EIT: The View from Sheffield EIT for Medical Applications at Oxford Brookes 1985-2003 The Rensselaer Experience APPENDIX A BRIEF INTRODUCTION TO BIOIMPEDANCE APPENDIX B NONTECHNICAL INTRODUCTION TO EIT

837 citations

Journal ArticleDOI
TL;DR: Electrical Impedance Tomography images were recorded with scalp electrodes and an EIT system, specially optimized for recording brain function, in 39 adult human subjects during visual, somatosensory, or motor activity and demonstrated significant impedance changes in the appropriate cortical region.

200 citations

Journal ArticleDOI
TL;DR: In this paper, a simplified reconstruction algorithm was used which modelled the head as a homogeneous sphere and incorporated realistic geometry and conductivity distributions using the finite element method, which significantly improved the quality of EIT images.

173 citations

Journal ArticleDOI
TL;DR: This work reports EIT imaging of impedance changes in rat somatosensory cerebral cortex with a resolution of 2 ms and < 200 μm during evoked potentials using epicortical arrays with 30 electrodes and indicates similar resolutions are feasible throughout the entire brain.

130 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

01 Jan 2016
TL;DR: As you may know, people have search numerous times for their chosen novels like this statistical parametric mapping the analysis of functional brain images, but end up in malicious downloads.
Abstract: Thank you very much for reading statistical parametric mapping the analysis of functional brain images. As you may know, people have search numerous times for their chosen novels like this statistical parametric mapping the analysis of functional brain images, but end up in malicious downloads. Rather than enjoying a good book with a cup of coffee in the afternoon, instead they cope with some infectious bugs inside their desktop computer.

1,719 citations

Journal ArticleDOI
TL;DR: A new approach combines independent component analysis (ICA), time/frequency analysis, and trial-by-trial visualization that measures EEG source dynamics without requiring an explicit head model.

1,377 citations

Journal Article
TL;DR: This is a paid internship where interns work directly to assist the Director of Marketing and Communications on various tasks relating to upcoming GRA events.
Abstract: OVERVIEW The GRA Marketing Internship Program is offered to students who are interested in gaining valuable work experience through efforts in marketing, membership, sales, and events. Interns work directly to assist the Director of Marketing and Communications on various tasks relating to upcoming GRA events. During this internship, students will work a minimum of 10 hours a week and a maximum of 20 hours a week. Students are encouraged to earn credit for their internship, however this is a paid internship. Students interested in obtaining credit for their internship must consult their academic advisor or the intern coordinator at their academic unit.

1,309 citations

Journal ArticleDOI
TL;DR: The current state-of-the-art of diffuse optical imaging is reviewed, which is an emerging technique for functional imaging of biological tissue and recent work on in vivo applications including imaging the breast and brain is reviewed.
Abstract: We review the current state-of-the-art of diffuse optical imaging, which is an emerging technique for functional imaging of biological tissue. It involves generating images using measurements of visible or near-infrared light scattered across large (greater than several centimetres) thicknesses of tissue. We discuss recent advances in experimental methods and instrumentation, and examine new theoretical techniques applied to modelling and image reconstruction. We review recent work on in vivo applications including imaging the breast and brain, and examine future challenges.

1,237 citations