Biomedical Engineering - Research Publications

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    Model Parameter Estimation As Features to Predict the Duration of Epileptic Seizures From Onset.
    Liu, Y ; Xia, S ; Soto-Breceda, A ; Karoly, P ; Cook, MJ ; Grayden, DB ; Schmidt, D ; Kuhlmann, L (IEEE, 2023-07)
    The durations of epileptic seizures are linked to severity and risk for patients. It is unclear if the spatiotemporal evolution of a seizure has any relationship with its duration. Understanding such mechanisms may help reveal treatments for reducing the duration of a seizure. Here, we present a novel method to predict whether a seizure is going to be short or long at its onset using features that can be interpreted in the parameter space of a brain model. The parameters of a Jansen-Rit neural mass model were tracked given intracranial electroencephalography (iEEG) signals, and were processed as time series features using MINIROCKET. By analysing 2954 seizures from 10 patients, patient-specific classifiers were built to predict if a seizure would be short or long given 7 s of iEEG at seizure onset. The method achieved an area under the receiver operating characteristic curve (AUC) greater than 0.6 for five of 10 patients. The behaviour in the parameter space has shown different mechanisms are associated with short/long seizures.Clinical relevance-This shows that it is possible to classify whether a seizure will be short or long based on its early characteristics. Timely interventions and treatments can be applied if the duration of the seizures can be predicted.
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    Establishing the Calibration Curve of a Compressive Ophthalmodynamometry Device.
    Kaplan, MA ; Bui, BV ; Ayton, LN ; Nguyen, B ; Grayden, DB ; John, S (IEEE, 2023-07)
    The relationship between externally applied force and intraocular pressure was determined using an ex-vivo porcine eye model (N=9). Eyes were indented through the sclera with a convex ophthalmodynamometry head (ODM). Intraocular pressure and ophthalmodynamometric force were simultaneously recorded to establish a calibration curve of this indenter head. A calibration coefficient of 0.140 ± 0.009 mmHg/mN was established and was shown to be highly linear (r = 0.998 ± 0.002). Repeat application of ODM resulted in a 0.010 ± 0.002 mmHg/mN increase to the calibration coefficient.Clinical Relevance- ODM has been highlighted as a potential method of non-invasively estimating intracranial pressure. This study provides relevant data for the practical performance of ODM with similar compressive devices.
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    Evidence of Onset and Sustained Neural Responses to Isolated Phonemes from Intracranial Recordings in a Voice-based Cursor Control Task
    Meng, K ; Lee, S-H ; Goodarzy, F ; Vogrin, S ; Cook, MJ ; Lee, S-W ; Grayden, DB (ISCA-INT SPEECH COMMUNICATION ASSOC, 2022)
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    Implementation of a closed-loop BCI system for real-time speech synthesis under clinical constraints
    Meng, K ; Kim, E ; Vogrin, S ; Cook, MJ ; Goodarzy, F ; Grayden, DB ; Chung, CK (IEEE, 2022)
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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.