Abstract

There is a growing interest in neuromorphic hardware since it offers a more intuitive way to achieve bio-inspired algorithms. This paper presents a neuromorphic model for intelligently processing continuous electrocardiogram (ECG) signal. This model aims to develop a hardware-based signal processing model and avoid employing digitally intensive operations, such as signal segmentation and feature extraction, which are not desired in an analogue neuromorphic system. We apply delay-based reservoir computing as the information processing core, along with a novel training and labelling method. Different from the conventional ECG classification techniques, this computation model is a end-to-end dynamic system that mimics the real-time signal flow in neuromorphic hardware. The input is the raw ECG stream, while the amplitude of the output represents the risk factor of a ventricular ectopic heartbeat. The intrinsic memristive property of the reservoir empowers the system to retain the historical ECG information for high-dimensional mapping. This model was evaluated with the MIT-BIH database under the inter-patient paradigm and yields 81% sensitivity and 98% accuracy. Under this architecture, the minimum size of memory required in the inference process can be as low as 3.1 MegaByte(MB) because the majority of the computation takes place in the analogue domain. Such computational modelling boosts memory efficiency by simplifying the computing procedure and minimizing the required memory for future wearable devices.

Highlights

  • C ARDIOVASCULAR diseases are the major sources of global mortality, which led to 17.9 million deaths in 2016 (WHO) [1]

  • After obtaining the output X in Eq (8), ideally, a spike would appear when a Ventricular Ectopic Beat (VEB) is sent to the model, whereas the output should keep flat for other types of ECG

  • F1 score, the harmonic mean of Se and positive predictivity (PP) is used to optimise the parameters. These values can be calculated using the values of True Positive (TP), True negative (TN), False Positive (FP) and False Negative (FN) [26]: S e = T P/(T P + FN)

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Summary

Introduction

C ARDIOVASCULAR diseases are the major sources of global mortality, which led to 17.9 million deaths in 2016 (WHO) [1]. Conventional software-based ECG classification methods can be divided into five steps: 1) ECG signal pre-processing, 2) analogue-todigital converter (ADC), 3) heartbeat segmentation, 4) feature extraction and 5) learning/classification [2] These widely used procedures, such as detection of the QRS complex, signal segmentation and feature extraction, critically rely on digital operations which are not desirable in neuromorphic hardware [2, 4, 19]. A prospective wearable device expects that the intelligent computing can be carried out at the local edge [21,22,23] Under such circumstances, a neuromorphic analogue processor based on the above-mentioned DRC architecture is well-suited to act as a direct interface to an ECG electrode with less memory requirement.

DRC design for ECG
Database
Delay-based reservoir computing for ECG processing
Lasso regression
Training data
Memory capacity
Post-processing
Performance matrix for VEB detection
Optimisation
Results
Minimum memory needed for inference
Comparison with the state-of-the-art
Findings
Discussion and conclusions
Full Text
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