MICA: Early thrombolytic intervention in acute stroke by imaging with Electrical Impedance Tomography

Lead Research Organisation: University College London
Department Name: Medical Physics and Biomedical Eng

Abstract

Electrical Impedance Tomography (EIT) is a novel medical imaging method in which tomographic "slice" images are rapidly produced using rings of electrodes placed around the body. It is safe, portable and inexpensive. The principal applicant's group has demonstrated that EIT can rapidly image functional brain activity in neurological conditions like stroke, epilepsy and normal activity in animal models and has developed systems which work well in head-shaped tanks.
Thrombolytic "clot-busting" treatment is a new treatment for acute stroke which must be given within three hours, but its take-up has been restricted because it is essential to undertake imaging of the head before it can be administered. This is because a sudden onset of weakness or disability which appears as a stroke, can be due to insufficient blood to a part of the brain or else bleeding into the brain. The clot-dissolving agent cannot be given until imaging has been used to assess if a bleed has occurred, as it could make the bleeding much worse with catastrophic consequences. EIT has the potential to provide an inexpensive portable unit for use in ambulances or GP surgeries which would revolutionise administration of this drug in acute stroke by providing imaging at the point of contact. This could be relayed over the internet to a radiologist who could then give permission for a paramedic to give the drug in the ambulance or in a remote centre.
The plan is to make three technical improvements in imaging and design of a helmet or headnet containing the contacts needed for accurate brain EIT and test these objectively in tanks, anaesthetised rats and human patient studies. The final outcome will be a new EIT system design optimised for imaging in acute stroke, with rigorous evaluation of its performance in about 30 patients.

Technical Summary

Electrical Impedance Tomography (EIT) is a novel medical imaging method in which tomographic images are rapidly produced using rings of electrodes placed around the body. It is safe, portable and inexpensive. The principal applicant's group has demonstrated that EIT can rapidly image functional brain activity in stroke, epilepsy and normal activity in animal models and has developed instrumentation and image reconstruction algorithms which work well in head-shaped tanks.
Thrombolytic "clot-busting" treatment is a new treatment for acute stroke which must be given within three hours, but its take-up has been restricted because it is essential to undertake neuroimaging first to exclude a haemorrhage. EIT has the potential to provide an inexpensive portable unit for use in ambulances or GP surgeries which would revolutionise thrombolytic management of stroke by providing imaging at the point of contact. This would be used to sanction administration of thrombolysis immediately by a paramedic or auxiliary health staff.
Support is requested for a collaboration between UCL and GE. While there is strong underpinning data to demonstrate proof of principle of the method, modelling and specification studies have indicated there are three tractable technical improvements needed to achieve breakthrough into clinical use. Support is requested for 3.5 post-doctoral research assistants over 2 years for the academic partner to apply innovations established in related fields to image reconstruction algorithms and electrode application to the scalp. GE will provide electronic hardware and commercial development.

Planned Impact

Stroke is a leading cause of death and long-term disability in the UK and is associated with high costs. Treatment with thrombolytic drugs is effective for ischaemic stroke but needs to be undertaken within three hours from the onset of symptoms. Neuroimaging is required prior to treatment onset to differentiate between ischaemic and hemorrhagic strokes, as thrombolysis is contraindicated in haemorrhage. Although about 60% of subjects are eligible for thrombolysis, only about 5% receive it, largely because of restricted or delayed access to CT or MRI scanners. This essential treatment is therefore being denied to patients due to lack of neuroimaging accessibility. There is therefore a pressing need for a practical economic neuroimaging system which could be used as early as possible after the onset of stroke. If it were portable, it could be available in ambulances and so enable earlier deployment of thrombolysis than any current method. Otherwise, it could be made available in GP surgeries or hospital A&E departments where specialist acute stroke centres were not currently available.

At present, EIT has only been demonstrated to provide reliable imaging of physiological changes over time, such as ventilation in the lungs. Since 3/11, it has been marketed for optimising ventilation in patients on long-term ventilation on ITU by Drager Medical. Until now, it has not successfully been deployed for situations where a single image in time is needed, such as in screening for breast cancer or imaging in stroke. The proposed technical advances would permit EIT imaging for "one-off" imaging and open up a large new area of medical imaging where the size and portability of EIT offer unique advantages. This could include cancer screening for breast, prostate or skin and monitoring for extradural haematoma after head injury.

If successful, EIT would become a standard imaging technique available in all ambulances and A&E departments for this purpose. It would be used in all cases of suspected stroke which present except to dedicated acute stroke centres. An estimated 150000 people have a stroke in the UK each year and 15M worldwide, of whom 5M die and 5M are permanently disabled. In 2009, only 1/3 of UK hospitals used thrombolysis (Rudd et al, JNNP, 2011) so the potential user base is 2/3 of all such staff in the UK.

The impact would therefore be of the highest international significance. It could yield a novel medical imaging method. In stroke, if it could increase the application of thrombolysis from its present level of 5% to say 20%, there would be substantial benefits in improved outcome and diminished cost to the NHS in rehabilitation for stroke which can be estimated to be £200M a year in the UK alone. In addition, it could set a precedent for the use of multifrequency EIT, which could be used in breast cancer screening and monitoring of head injury. Finally, there could be academic benefits for researchers working in several of the interdisciplinary fields in which development will be undertaken - maths, numerical modelling, electrode design and neurology and cardiovascular medicine.

Publications


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Chaulet N (2015) Electromagnetic inverse shape problem for coated obstacles in Advances in Computational Mathematics
Doru T (2013) A new 3D head shaped tank containing a human skull phantom construction for electrical impedance tomography in XVth International Conference of Electrical Bioimpedance and XIVth conference on Electrical Impedance Tomography, Heiligenstadt, Germany, April, 2013.
Jehl Markus (2013) A Parallel Solver for the Forward Problem in Electrical Impedance Tomography using DUNE FEM. in XVth International Conference of Electrical Bioimpedance and XIVth conference on Electrical Impedance Tomography, Heiligenstadt, Germany, April, 2013
Koronfel M (2013) ) A flexible polyimide epicortical electrode array for imaging fast neural activity in the rat cortex using EIT in . XVth International Conference of Electrical Bioimpedance and XIVth conference on Electrical Impedance Tomography, Heiligenstadt, Germany, April, 2013.
Malone E (2014) Multifrequency electrical impedance tomography using spectral constraints. in IEEE transactions on medical imaging
 
Title Electronic hardware for Electrical Impedance Tomography in the human head 
Description Electronic hardware for collecting images in acute stroke for Electrical Impedance Tomography 
Type Of Material Technology assay or reagent 
Provided To Others? No  
Impact To form the basis for a commercial system by Blackrock Microsystems 
 
Title Software for image reconstruction for Electrical Impedance Tomography in stroke in the adult human head 
Description Software suite which enables tomographic images of acute stroke or haemorrhage in the brain using scalp electrodes. 
Type Of Material Technology assay or reagent 
Provided To Others? No  
Impact None yet. Will have major international impact when used in subjects with acute stroke. 
 
Title Electrode assembly 
Description US patent on automated electrode helmet for EIT and EEG recording 
IP Reference WO2013177126 
Protection Patent application published
Year Protection Granted 2013
Licensed No
Impact None yet; to be used in MRC trial
 
Title Method of imaging 
Description US patent on frequency difference image reconstruction algorithm for Electrical Impedance Tomography 
IP Reference WO2013177123 
Protection Patent application published
Year Protection Granted 2013
Licensed No
Impact None yet but interest from major international medical device company