Learned Kernels for Interpretable and Efficient Medical Time Series Processing

Background: Signal processing methods are the foundation for clinical interpretation across a wide variety of medical applications. The advent of deep learning allowed for an explosion of new models that offered unprecedented performance but at a cost: deep learning models are often compute-intensive and lack interpretability. Methods: We propose a sparse, interpretable architecture for medical time series processing. The method learns a set of lightweight flexible kernels to construct a single-layer neural network, providing a new efficient, robust, and interpretable approach. We introduce novel parameter reduction techniques to further reduce the size of our network. We demonstrate the power of our architecture on the important task of photoplethysmography artifact detection, where our approach has performance similar to the state-of-the-art deep neural networks with several orders of magnitude fewer parameters, allowing for the integration of deep neural network level performance into extremely low-power wearable devices. Results: Our interpretable method achieves greater than 99\% of the performance of the state-of-the-art methods on the artifact detection task, and even outperforms the state-of-the-art on a challenging out-of-distribution test set, while using dramatically fewer parameters (2\% of the parameters of Segade, and about half of the parameters of Tiny-PPG). Conclusions: Learned kernels are competitive with deep neural networks for medical time series processing with dramatically fewer parameters. Our method is particularly suited for real-time applications and low-power devices, and it maintains interpretability.