About Dr Alistair McEwan

Alistair's research investigates medical instrumentation, biomedical devices and integrated circuit design.

Most recently he developed a portable imaging device based on Electrical Impedance Tomography Spectroscopy (EITS). The resulting system is currently being used in clinical trials of stroke and epilepsy monitoring in three London hospitals. While developing this system he published an extensive review of the errors in EITS systems and developed a code division multiplexing (CDM) EITS method for simultaneous measurements with increased acquisition speed, number of electrodes and frequencies, leading to improved images and a wider range of applications. This has been patented and attracted commercial attention of Philips Research Laboratories (Germany) and GE Research (USA). He has made significant contributions in the fields of low power circuit design and neuromorphic engineering with an integrated circuit which mimics the behaviour of the inner hair cell of the ear. He has also developed, with funding from Analog Devices (UK), an integrated circuit which provides low power, low cost frequency synthesis for communications such as Bluetooth and which enables the integration of large arrays of these synthesisers for a lab-on-a-chip or bio-impedance measurements. The design is currently the most efficient direct digital frequency synthesiser available.

Selected publications

(1) McEwan, A. Romsauerova A., Yerworth R.,  Horesh L,  Bayford R and Holder, D.S. “Design and calibration of a compact multi-frequency EIT system for acute stroke imaging,” 2006, Physiol. Meas., 27, 199-210. (2) McEwan, A., Cusick, G. and Holder, D.S. “A Review of Errors in Multi-frequency EIT Instrumentation,” 2007, Physiol. Meas., 28, S197-215. (3) Romsauerova, A., McEwan, A. and Holder, D.S., “Identification of a suitable current waveform for acute stroke imaging,” 2006, Physiol.Meas., 27, 211-219. (4) Fabrizi L., McEwan A., Woo E. and Holder, D. “Analysis of resting noise characteristics of three EIT systems in order to optimise time difference imaging with scalp electrodes during epileptic seizures.” 2007, Physiol. Meas., 28, S217-236. (5) Fabrizi, L., Horesh, L., McEwan, A., Holder, D. “Estimation of signal size for imaging of epileptic seizures by electrical impedance tomography (EIT),” 2007, Clinical Neurophysiology, 118:6, e183-183. (6) Fabrizi, L., Sparkes, M., Horesh, L., Perez-Juste Abascal, J., McEwan, A., Bayford, R.H., Elwes, R., Binnie, C.D. and Holder, D.S., “Factors limiting the application of electrical impedance tomography for identification of regional conductivity changes using scalp electrodes during epileptic seizures in humans,” 2006, Physiol. Meas., 27, 163-174. (7) Romsauerova, A., McEwan, A., Horesh, L., Yerworth, R., Bayford, R., and Holder, D.S., “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,” 2006, Physiol. Meas., 27, 147-161. (8) McEwan, A., and Collins, S., “Direct Digital Frequency Synthesis by Analogue Interpolation,” 2006, IEEE Transactions on Circuits and Systems II, 53:11. 1294-1298. (9) McEwan, A., and Collins, S., “Efficient, ROM-less DDFS using non-linear interpolation and non-linear DAC 2006,” Analog Integrated Circuits and Signal Processing 48:3 231-237. (10) McEwan, A., and van Schaik, A., “An analogue VLSI implementation of the Meddis inner hair cell model,” EURASIP Journal on Applied Signal Processing, 2003, 7, 639-648.