Biomedical Engineering - Research Publications
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ItemNo Preview AvailableVisual evoked potentials determine chronic signal quality in a stent-electrode endovascular neural interfaceGerboni, G ; John, SE ; Rind, GS ; Ronayne, SM ; May, CN ; Oxley, TJ ; Grayden, DB ; Opie, NL ; Wong, YT (IOP PUBLISHING LTD, 2018-09-01)
ItemSignal quality of simultaneously recorded endovascular, subdural and epidural signals are comparable (vol 8, 8427, 2018)John, SE ; Opie, NL ; Wong, YT ; Rind, GS ; Ronayne, SM ; Gerboni, G ; Bauquier, SH ; O'Brien, TJ ; May, CN ; Grayden, DB ; Oxley, TJ (NATURE PUBLISHING GROUP, 2018-11-27)
ItemSignal quality of simultaneously recorded endovascular, subdural and epidural signals are comparableJohn, SE ; Opie, NL ; Wong, YT ; Rind, GS ; Ronayne, SM ; Gerboni, G ; Bauquier, SH ; O'Brien, TJ ; May, CN ; Grayden, DB ; Oxley, TJ (NATURE PUBLISHING GROUP, 2018-05-30)Recent work has demonstrated the feasibility of minimally-invasive implantation of electrodes into a cortical blood vessel. However, the effect of the dura and blood vessel on recording signal quality is not understood and may be a critical factor impacting implementation of a closed-loop endovascular neuromodulation system. The present work compares the performance and recording signal quality of a minimally-invasive endovascular neural interface with conventional subdural and epidural interfaces. We compared bandwidth, signal-to-noise ratio, and spatial resolution of recorded cortical signals using subdural, epidural and endovascular arrays four weeks after implantation in sheep. We show that the quality of the signals (bandwidth and signal-to-noise ratio) of the endovascular neural interface is not significantly different from conventional neural sensors. However, the spatial resolution depends on the array location and the frequency of recording. We also show that there is a direct correlation between the signal-noise-ratio and classification accuracy, and that decoding accuracy is comparable between electrode arrays. These results support the consideration for use of an endovascular neural interface in a clinical trial of a novel closed-loop neuromodulation technology.
ItemNo Preview AvailableFeasibility of a Chronic, Minimally Invasive Endovascular Neural InterfaceOpie, NL ; Rind, GS ; John, SE ; Ronayne, SM ; Grayden, DB ; Burkitt, AN ; May, CN ; O'Brien, TJ ; Oxley, TJ ; Patton, J ; Barbieri, R ; Ji, J ; Jabbari, E ; Dokos, S ; Mukkamala, R ; Guiraud, D ; Jovanov, E ; Dhaher, Y ; Panescu, D ; Vangils, M ; Wheeler, B ; Dhawan, AP (IEEE, 2016-01-01)Development of a neural interface that can be implanted without risky, open brain surgery will increase the safety and viability of chronic neural recording arrays. We have developed a minimally invasive surgical procedure and an endovascular electrode-array that can be delivered to overlie the cortex through blood vessels. Here, we describe feasibility of the endovascular interface through electrode viability, recording potential and safety. Electrochemical impedance spectroscopy demonstrated that electrode impedance was stable over 91 days and low frequency phase could be used to infer electrode incorporation into the vessel wall. Baseline neural recording were used to identify the maximum bandwidth of the neural interface, which remained stable around 193 Hz for six months. Cross-sectional areas of the implanted vessels were non-destructively measured using the Australian Synchrotron. There was no case of occlusion observed in any of the implanted animals. This work demonstrates the feasibility of an endovascular neural interface to safely and efficaciously record neural information over a chronic time course.
Item7T-fMRI: Faster temporal resolution yields optimal BOLD sensitivity for functional network imaging specifically at high spatial resolutionYoo, PE ; John, SE ; Farquharson, S ; Cleary, JO ; Wong, YT ; Ng, A ; Mulcahy, CB ; Grayden, DB ; Ordidge, RJ ; Opie, NL ; O'Brien, TJ ; Oxley, TJ ; Moffat, BA (ACADEMIC PRESS INC ELSEVIER SCIENCE, 2018-01-01)Recent developments in accelerated imaging methods allow faster acquisition of high spatial resolution images. This could improve the applications of functional magnetic resonance imaging at 7 Tesla (7T-fMRI), such as neurosurgical planning and Brain Computer Interfaces (BCIs). However, increasing the spatial and temporal resolution will both lead to signal-to-noise ratio (SNR) losses due to decreased net magnetization per voxel and T1-relaxation effect, respectively. This could potentially offset the SNR efficiency gains made with increasing temporal resolution. We investigated the effects of varying spatial and temporal resolution on fMRI sensitivity measures and their implications on fMRI-based BCI simulations. We compared temporal signal-to-noise ratio (tSNR), observed percent signal change (%∆S), volumes of significant activation, Z-scores and decoding performance of linear classifiers commonly used in BCIs across a range of spatial and temporal resolution images acquired during an ankle-tapping task. Our results revealed an average increase of 22% in %∆S (p=0.006) and 9% in decoding performance (p=0.015) with temporal resolution only at the highest spatial resolution of 1.5×1.5×1.5mm3, despite a 29% decrease in tSNR (p<0.001) and plateaued Z-scores. Further, the volume of significant activation was indifferent (p>0.05) across spatial resolution specifically at the highest temporal resolution of 500ms. These results demonstrate that the overall BOLD sensitivity can be increased significantly with temporal resolution, granted an adequately high spatial resolution with minimal physiological noise level. This shows the feasibility of diffuse motor-network imaging at high spatial and temporal resolution with robust BOLD sensitivity with 7T-fMRI. Importantly, we show that this sensitivity improvement could be extended to an fMRI application such as BCIs.