ABSTRACT Electrical Impedance Tomography (EIT) could be used as a rapid and non-invasive technique to image/diagnose ischaemic or haemorrhagic stroke. However, there are currently no suitable imaging/classification methods which which can be applied to human stroke data. In part this is due to the complexity of the problem itself, but it is also affected by a lack of available data on which to evaluate different techniques. Multi-frequency EIT data (alongside MRI/CT) has been collected on 23 stroke patients, and 10 healthy volunteers, as part of a clinical trial in collaboration with the Hyper Acute Stroke Unit (HASU) at University College London Hospital (UCLH). Data was collected at 17 frequencies between 5Hz and 2kHz, with 31 current injections, yielding 930 measurements at each frequency. The raw data, collected simultaneous on all channel using an EEG amplifier sampling at 16kHz, is also made available. BIT MORE MAYBE
ABSTRACT A highly versatile EIT system, nicknamed the ScouseTom, has been developed. The system allows control over current amplitude, frequency, number of electrodes, injection protocol and data processing. A Keithley 6221 current source is used, along with a 24-bit EEG system for voltage recording. Custom PCBs interface with a PC to control the measurement process, electrode addressing and triggering external stimuli. The performance of the system has been characterised using resistor phantoms in experiments representative of human scalp recordings, with an overall SNR of 77.5 dB (n=343), stable across a four hour recording and across frequencies from 20 Hz to 20 kHz. The ScouseTom was used successfully in four modes of operation: time difference, triggered averaging, multi-frequency EIT and impedance spectrum measurements, in experiments investigating stroke and evoked potentials in both rat and human recordings. The experimental procedure is controlled by software and is readily adaptable to new paradigms. Where possible, commercial or open-source components have been used, to minimise the cost and complexity in reproduction. All of the hardware designs and software for the system have been released under an open source licence, encouraging contributions and allowing for rapid replication.