{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,12]],"date-time":"2025-10-12T03:27:33Z","timestamp":1760239653206,"version":"build-2065373602"},"reference-count":50,"publisher":"MDPI AG","issue":"24","license":[{"start":{"date-parts":[[2020,12,9]],"date-time":"2020-12-09T00:00:00Z","timestamp":1607472000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100013342","name":"NIHR Imperial BRC","doi-asserted-by":"publisher","award":["N\/A"],"award-info":[{"award-number":["N\/A"]}],"id":[{"id":"10.13039\/501100013342","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Electrical Impedance Tomography (EIT) is a medical imaging technique which has the potential to reduce time to treatment in acute stroke by rapidly differentiating between ischaemic and haemorrhagic stroke. The potential of these methods has been demonstrated in simulation and phantoms, it has not yet successfully translated to clinical studies, due to high sensitivity to errors in scalp electrode mislocation and poor electrode-skin contact. To overcome these limitations, a novel electrode helmet was designed, bearing 32 independently controlled self-abrading electrodes. The contact impedance was reduced through rotation on an abrasive electrode on the scalp using a combined impedance, rotation and position feedback loop. Potentiometers within each unit measure the electrode tip displacement within 0.1 mm from the rigid helmet body. Characterisation experiments on a large-scale test rig demonstrated that approximately 20 kPa applied pressure and 5 rotations was necessary to achieve the target 5 k\u03a9 contact impedance at 20 Hz. This performance was then replicated in a simplified self-contained unit where spring loaded electrodes are rotated by servo motors. Finally, a 32-channel helmet and controller which sequentially minimised contact impedance and simultaneously located each electrode was built which reduced the electrode application and localisation time to less than five minutes. The results demonstrated the potential of this approach to rapidly apply electrodes in an acute setting, removing a significant barrier for imaging acute stroke with EIT.<\/jats:p>","DOI":"10.3390\/s20247058","type":"journal-article","created":{"date-parts":[[2020,12,10]],"date-time":"2020-12-10T08:59:34Z","timestamp":1607590774000},"page":"7058","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Self-Abrading Servo Electrode Helmet for Electrical Impedance Tomography"],"prefix":"10.3390","volume":"20","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-4015-1802","authenticated-orcid":false,"given":"James","family":"Avery","sequence":"first","affiliation":[{"name":"Department of Surgery and Cancer, Imperial College London, London SW7 2AZ, UK"},{"name":"Department Medical Physics and Biomedical Engineering, University College London, London WC1E 6BT, UK"}]},{"given":"Brett","family":"Packham","sequence":"additional","affiliation":[{"name":"Department Medical Physics and Biomedical Engineering, University College London, London WC1E 6BT, UK"}]},{"given":"Hwan","family":"Koo","sequence":"additional","affiliation":[{"name":"Department Medical Physics and Biomedical Engineering, University College London, London WC1E 6BT, UK"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4661-6778","authenticated-orcid":false,"given":"Ben","family":"Hanson","sequence":"additional","affiliation":[{"name":"Department of Mechanical Engineering, University College London, London WC1E 7JE, UK"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2755-6124","authenticated-orcid":false,"given":"David","family":"Holder","sequence":"additional","affiliation":[{"name":"Department Medical Physics and Biomedical Engineering, University College London, London WC1E 6BT, UK"}]}],"member":"1968","published-online":{"date-parts":[[2020,12,9]]},"reference":[{"key":"ref_1","first-page":"e85","article-title":"Heart disease and stroke statistics\u20142006 update: A report from the American Heart Association Statistics Committee and Stroke Statistics Subcommittee","volume":"113","author":"Thom","year":"2006","journal-title":"Circulation"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"2257","DOI":"10.1016\/S0140-6736(15)00195-6","article-title":"Changes in health in England, with analysis by English regions and areas of deprivation, 1990\u20132013: A systematic analysis for the Global Burden of Disease Study 2013","volume":"386","author":"Newton","year":"2015","journal-title":"Lancet"},{"key":"ref_3","unstructured":"Stroke Association (2015). Current, Future and Avoidable Costs of Stroke in the UK, Stroke Association."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"29","DOI":"10.1007\/s11910-009-0076-8","article-title":"Evolution of the thrombolytic treatment window for acute ischemic stroke","volume":"10","author":"Stemer","year":"2010","journal-title":"Curr. Neurol. Neurosci. Rep."},{"key":"ref_5","unstructured":"NICE (2019). Stroke and transient ischaemic attack in over 16s: Diagnosis and initial management. Nice Guideline, National Institute for Health Care Excellence."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"2935","DOI":"10.1161\/01.STR.0000249057.44420.4b","article-title":"An expedited code stroke protocol is feasible and safe","volume":"37","author":"Sattin","year":"2006","journal-title":"Stroke"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"49","DOI":"10.1007\/s10072-013-1484-8","article-title":"Delay in presentation after acute ischemic stroke: The Careggi Hospital Stroke Registry","volume":"35","author":"Eleonora","year":"2014","journal-title":"Neurol. Sci."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"1232","DOI":"10.1161\/01.STR.0000165902.18021.5b","article-title":"Acute stroke care in the US: Results from 4 pilot prototypes of the Paul Coverdell National Acute Stroke Registry","volume":"36","author":"Reeves","year":"2005","journal-title":"Stroke"},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"Holder, D.S. (2004). Electrical Impedance Tomography: Methods, History and Applications, CRC Press.","DOI":"10.1201\/9781420034462.ch4"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"S147","DOI":"10.1088\/0967-3334\/27\/5\/S13","article-title":"Multi-frequency electrical impedance tomography (EIT) of the adult human head: Initial findings in brain tumours, arteriovenous malformations and chronic stroke, development of an analysis method and calibration","volume":"27","author":"Romsauerova","year":"2006","journal-title":"Physiol. Meas."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"1273","DOI":"10.1088\/0967-3334\/36\/6\/1273","article-title":"In vivo bioimpedance measurement of healthy and ischaemic rat brain: Implications for stroke imaging using electrical impedance tomography","volume":"36","author":"Dowrick","year":"2015","journal-title":"Physiol. Meas."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"355","DOI":"10.1111\/j.1748-1716.1980.tb06544.x","article-title":"Brain extracellular space during spreading depression and ischemia","volume":"108","author":"Hansen","year":"1980","journal-title":"Acta Physiol. Scand."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"825","DOI":"10.1007\/s10548-019-00710-2","article-title":"Variation in Reported Human Head Tissue Electrical Conductivity Values","volume":"32","author":"McCann","year":"2019","journal-title":"Brain Topogr."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"125","DOI":"10.1088\/0967-3334\/25\/1\/021","article-title":"EIT reconstruction algorithms: Pitfalls, challenges and recent developments","volume":"25","author":"Lionheart","year":"2004","journal-title":"Physiol. Meas."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"1051","DOI":"10.1088\/0967-3334\/35\/6\/1051","article-title":"Stroke type differentiation using spectrally constrained multifrequency EIT: Evaluation of feasibility in a realistic head model","volume":"35","author":"Malone","year":"2014","journal-title":"Physiol. Meas."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"2317","DOI":"10.1088\/1361-6579\/37\/12\/2317","article-title":"A novel multi-frequency electrical impedance tomography spectral imaging algorithm for early stroke detection","volume":"37","author":"Yang","year":"2016","journal-title":"Physiol. Meas."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"1486","DOI":"10.1109\/TMI.2015.2402661","article-title":"A Reconstruction-Classification Method for Multifrequency Electrical Impedance Tomography","volume":"34","author":"Malone","year":"2015","journal-title":"IEEE Trans. Med. Imaging"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"044005","DOI":"10.1088\/1361-6579\/ab08ba","article-title":"Bi-frequency symmetry difference electrical impedance tomography\u2014A novel technique for perturbation detection in static scenes","volume":"40","author":"McDermott","year":"2019","journal-title":"Physiol. Meas."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"2423","DOI":"10.1088\/0967-3334\/36\/12\/2423","article-title":"Correcting electrode modelling errors in EIT on realistic 3D head models","volume":"36","author":"Jehl","year":"2015","journal-title":"Physiol. Meas."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"893","DOI":"10.1088\/0967-3334\/37\/6\/893","article-title":"Correction of electrode modelling errors in multi-frequency EIT imaging","volume":"37","author":"Jehl","year":"2016","journal-title":"Physiol. Meas."},{"key":"ref_21","first-page":"1","article-title":"Bi-Frequency Symmetry Difference EIT\u2014Feasibility and Limitations of Application to Stroke Diagnosis","volume":"2194","author":"McDermott","year":"2019","journal-title":"IEEE J. Biomed. Health Inform."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"801","DOI":"10.1088\/0967-3334\/33\/5\/801","article-title":"A method for rapid production of subject specific finite element meshes for electrical impedance tomography of the human head","volume":"33","author":"Vonach","year":"2012","journal-title":"Physiol. Meas."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"879","DOI":"10.1088\/0967-3334\/37\/6\/879","article-title":"Are patient specific meshes required for EIT head imaging?","volume":"37","author":"Jehl","year":"2016","journal-title":"Physiol. Meas."},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"McDermott, B.J., Elahi, A., Santorelli, A., O\u2019Halloran, M., Avery, J., and Porter, E. (2020). Multi-frequency symmetry difference electrical impedance tomography with machine learning for human stroke diagnosis. Physiol. Meas.","DOI":"10.1088\/1361-6579\/ab9e54"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"983","DOI":"10.1007\/s10439-010-0230-0","article-title":"EEG-MRI co-registration and sensor labeling using a 3D laser scanner","volume":"39","author":"Koessler","year":"2011","journal-title":"Ann. Biomed. Eng."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"95186","DOI":"10.1109\/ACCESS.2019.2928580","article-title":"Real-Time Monitoring of Contact Impedance from Multiple Electrode-Scalp Interfaces during Cerebral Electrical Impedance Tomography","volume":"7","author":"Ma","year":"2019","journal-title":"IEEE Access"},{"key":"ref_27","doi-asserted-by":"crossref","unstructured":"Li, H., Liu, X., Xu, C., Yang, B., Fu, D., Dong, X., and Fu, F. (2020). Managing erroneous measurements of dynamic brain electrical impedance tomography after reconnection of faulty electrodes. Physiol. Meas., 41.","DOI":"10.1088\/1361-6579\/ab71f4"},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"180112","DOI":"10.1038\/sdata.2018.112","article-title":"Multi-frequency electrical impedance tomography and neuroimaging data in stroke patients","volume":"5","author":"Goren","year":"2018","journal-title":"Sci. Data"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"527","DOI":"10.1088\/0967-3334\/24\/2\/363","article-title":"A comparison of headnet electrode arrays for electrical impedance tomography of the human head","volume":"24","author":"Tidswell","year":"2003","journal-title":"Physiol. Meas."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"108378","DOI":"10.1016\/j.jneumeth.2019.108378","article-title":"Using a structured-light 3D scanner to improve EEG source modeling with more accurate electrode positions","volume":"326","author":"Oostenveld","year":"2019","journal-title":"J. Neurosci. Methods"},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"105","DOI":"10.1007\/s10548-007-0036-z","article-title":"Variability of electrode positions using electrode caps","volume":"20","author":"Atcherson","year":"2007","journal-title":"Brain Topogr."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"1130","DOI":"10.1016\/j.clinph.2004.12.022","article-title":"Geodesic photogrammetry for localizing sensor positions in dense-array EEG","volume":"116","author":"Russell","year":"2005","journal-title":"Clin. Neurophysiol."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"42","DOI":"10.3389\/fnins.2014.00042","article-title":"Consequences of EEG electrode position error on ultimate beamformer source reconstruction performance","volume":"8","author":"Dalal","year":"2014","journal-title":"Front. Neurosci."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"119","DOI":"10.1109\/TBCAS.2013.2256785","article-title":"Multi-frequency electrical impedance tomography system with automatic self-calibration for long-term monitoring","volume":"8","author":"Wi","year":"2014","journal-title":"IEEE Trans. Biomed. Circuits Syst."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"835","DOI":"10.1088\/0967-3334\/32\/7\/S08","article-title":"A fully parallel multi-frequency EIT system with flexible electrode configuration: KHU Mark2","volume":"32","author":"Oh","year":"2011","journal-title":"Physiol. Meas."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"21","DOI":"10.1109\/TBCAS.2014.2311836","article-title":"Active Electrode IC for EEG and Electrical Impedance Tomography with Continuous Monitoring of Contact Impedance","volume":"9","author":"Guermandi","year":"2014","journal-title":"IEEE Trans. Biomed. Circuits Syst."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"74","DOI":"10.1111\/psyp.12536","article-title":"High and dry? Comparing active dry EEG electrodes to active and passive wet electrodes","volume":"54","author":"Mathewson","year":"2017","journal-title":"Psychophysiology"},{"key":"ref_38","first-page":"143","article-title":"Design and electrical characteristics of an electrode array for electrical impedance tomography of the female breast","volume":"16","author":"Holder","year":"1995","journal-title":"Innov. Technol. Biol. Med."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"S163","DOI":"10.1088\/0967-3334\/27\/5\/S14","article-title":"Factors limiting the application of electrical impedance tomography for identification of regional conductivity changes using scalp electrodes during epileptic seizures in humans","volume":"27","author":"Fabrizi","year":"2006","journal-title":"Physiol. Meas."},{"key":"ref_40","unstructured":"Turner, J., and Jacques, R. (2018). Ambulance Response Programme Spring Review, University of Sheffield. Technical Report."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"151","DOI":"10.1007\/BF02478741","article-title":"Electrical properties of the epidermal stratum corneum","volume":"14","author":"Yamamoto","year":"1976","journal-title":"Med. Biol. Eng."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"555","DOI":"10.1007\/s004030050453","article-title":"Number of cell layers of the stratum corneum in normal skin relationship to the anatomical location an the body, age, sex and physical parameters","volume":"291","author":"Zhen","year":"1999","journal-title":"Arch. Dermatol. Res."},{"key":"ref_43","doi-asserted-by":"crossref","unstructured":"Meckl, P.H., Arestides, P.B., and Woods, M.C. (1998, January 26). Optimized S-curve motion profiles for minimum residual vibration. Proceedings of the 1998 American Control Conference, Philadelphia, PA, USA.","DOI":"10.1109\/ACC.1998.688324"},{"key":"ref_44","unstructured":"Motmans, R., and Ceriez, E. (2005). DinBelg 2005: Body Dimensions of the Belgian Population, Ergonomie RC. Technical Report."},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"1116","DOI":"10.1088\/1361-6579\/aa6586","article-title":"Reproducible 3D printed head tanks for electrical impedance tomography with realistic shape and conductivity distribution","volume":"38","author":"Avery","year":"2017","journal-title":"Physiol. Meas."},{"key":"ref_46","doi-asserted-by":"crossref","unstructured":"Avery, J., Dowrick, T., Faulkner, M., Goren, N., and Holder, D. (2017). A Versatile and Reproducible Multi-Frequency Electrical Impedance Tomography System. Sensors, 17.","DOI":"10.3390\/s17020280"},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"174","DOI":"10.1007\/s10548-017-0610-y","article-title":"A Preliminary Study on Precision Image Guidance for Electrode Placement in an EEG Study","volume":"31","author":"Jeon","year":"2018","journal-title":"Brain Topogr."},{"key":"ref_48","unstructured":"Arbogast, K.B., Margulies, S.S., Patlak, M., Fenner, H., and Thomas, D.J. (2003). Review of Pediatric Head and Neck Injury: Implications for Helmet Standards, The Childrens Hospital of Philadelphia. Technical Report."},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"87","DOI":"10.1515\/JPM.2008.009","article-title":"Quantification of impulse experienced by neonates during inter- and intra-hospital transport measured by biophysical accelerometery","volume":"36","author":"Shah","year":"2008","journal-title":"J. Perinat. Med."},{"key":"ref_50","doi-asserted-by":"crossref","first-page":"391","DOI":"10.1088\/0967-3334\/34\/4\/391","article-title":"A four-electrode low frequency impedance spectroscopy measurement system using the AD5933 measurement chip","volume":"34","author":"Margo","year":"2013","journal-title":"Physiol. Meas."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/20\/24\/7058\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T10:42:58Z","timestamp":1760179378000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/20\/24\/7058"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2020,12,9]]},"references-count":50,"journal-issue":{"issue":"24","published-online":{"date-parts":[[2020,12]]}},"alternative-id":["s20247058"],"URL":"https:\/\/doi.org\/10.3390\/s20247058","relation":{},"ISSN":["1424-8220"],"issn-type":[{"type":"electronic","value":"1424-8220"}],"subject":[],"published":{"date-parts":[[2020,12,9]]}}}