Biomedical Engineering - Research Publications

Permanent URI for this collection

Search Results

Now showing 1 - 7 of 7
  • Item
    No Preview Available
    The evolution of endovascular electroencephalography: historical perspective and future applications
    Sefcik, RK ; Opie, NL ; John, SE ; Kellner, CP ; Mocco, J ; Oxley, TJ (AMER ASSOC NEUROLOGICAL SURGEONS, 2016-05)
    Current standard practice requires an invasive approach to the recording of electroencephalography (EEG) for epilepsy surgery, deep brain stimulation (DBS), and brain-machine interfaces (BMIs). The development of endovascular techniques offers a minimally invasive route to recording EEG from deep brain structures. This historical perspective aims to describe the technical progress in endovascular EEG by reviewing the first endovascular recordings made using a wire electrode, which was followed by the development of nanowire and catheter recordings and, finally, the most recent progress in stent-electrode recordings. The technical progress in device technology over time and the development of the ability to record chronic intravenous EEG from electrode arrays is described. Future applications for the use of endovascular EEG in the preoperative and operative management of epilepsy surgery are then discussed, followed by the possibility of the technique's future application in minimally invasive operative approaches to DBS and BMI.
  • Item
    No Preview Available
    Visual evoked potentials determine chronic signal quality in a stent-electrode endovascular neural interface
    Gerboni, G ; John, SE ; Rind, GS ; Ronayne, SM ; May, CN ; Oxley, TJ ; Grayden, DB ; Opie, NL ; Wong, YT (IOP PUBLISHING LTD, 2018-09)
  • Item
    Thumbnail Image
    Signal 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 PORTFOLIO, 2018-11-27)
    A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.
  • Item
    Thumbnail Image
    Signal quality of simultaneously recorded endovascular, subdural and epidural signals are comparable
    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, 2018-05-30)
    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.
  • Item
    Thumbnail Image
    Feasibility of identifying the ideal locations for motor intention decoding using unimodal and multimodal classification at 7T-fMRI
    Yoo, PE ; Oxley, TJ ; John, SE ; Opie, NL ; Ordidge, RJ ; O'Brien, TJ ; Hagan, MA ; Wong, YT ; Moffat, BA (NATURE PUBLISHING GROUP, 2018-10-22)
    Invasive Brain-Computer Interfaces (BCIs) require surgeries with high health-risks. The risk-to-benefit ratio of the procedure could potentially be improved by pre-surgically identifying the ideal locations for mental strategy classification. We recorded high-spatiotemporal resolution blood-oxygenation-level-dependent (BOLD) signals using functional MRI at 7 Tesla in eleven healthy participants during two motor imagery tasks. BCI diagnostic task isolated the intent to imagine movements, while BCI simulation task simulated the neural states that may be yielded in a real-life BCI-operation scenario. Imagination of movements were classified from the BOLD signals in sub-regions of activation within a single or multiple dorsal motor network regions. Then, the participant's decoding performance during the BCI simulation task was predicted from the BCI diagnostic task. The results revealed that drawing information from multiple regions compared to a single region increased the classification accuracy of imagined movements. Importantly, systematic unimodal and multimodal classification revealed the ideal combination of regions that yielded the best classification accuracy at the individual-level. Lastly, a given participant's decoding performance achieved during the BCI simulation task could be predicted from the BCI diagnostic task. These results show the feasibility of 7T-fMRI with unimodal and multimodal classification being utilized for identifying ideal sites for mental strategy classification.
  • Item
    No Preview Available
    Feasibility of a Chronic, Minimally Invasive Endovascular Neural Interface
    Opie, 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)
    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.
  • Item
    Thumbnail Image
    7T-fMRI: Faster temporal resolution yields optimal BOLD sensitivity for functional network imaging specifically at high spatial resolution
    Yoo, 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.