Biomedical Engineering - Research Publications

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Type: Conference Paper × Author: John, Sam ×

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    Non-Invasive Measurement of Intracranial Pressure Through Application of Venous Ophthalmodynamometry.
    Lo, L ; Zhao, D ; Ayton, L ; Grayden, D ; Bui, B ; Morokoff, A ; John, S (IEEE, 2021-11)
    Non-invasive intracranial pressure (ICP) monitoring is possible using venous ophthalmodynamometry to observe a pulsation in retinal blood vessels when intraocular pressure (IOP) exceeds ICP. Here, we identify features in the eye - optic disc and retinal blood vessel locations - and identify pulsation in large retinal blood vessels. The relationship between force and the magnitude of pulsation is used to estimate ICP when force is applied to the eye to gradually increase IOP over time. This approach yields 77% accuracy in automatically observing vessel pulsation.Clinical Relevance - Non-invasive ICP monitoring is desirable to improve patient outcome by reducing potential trauma and complications associated with invasive assessment with intracranial sensors or lumbar puncture.
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    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, 2016-01-01)
    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.