A Machine Learning Pipeline for Measurement of Arterial Stiffness in A-Mode Ultrasound.

Arterial stiffness (AS) of the carotid artery is an early marker of stratifying cardiovascular disease risk. This paper aims to improve performance of ARTSENS, a non-invasive A-mode ultrasound-based device for measuring AS. The primary objective of ARTSENS is to enable measurement of elastic modulus using A-Mode ultrasound and Blood pressure. As this device is image-free, there is a need to automate - a) carotid detection, b) wall localization and c) inner lumen diameter measurement. This has been performed using conventional signal processing methods in some of the earlier works in this domain. In this paper, deep neural network (DNN) models are employed to perform the above three tasks. The DNNs were trained over data acquired from 82 subjects at two different medical centers. Ground truth labeling was performed by a trained operator using corresponding measurements from state-of-the-art Aloka e-Tracking system. All three DNN models had significantly lower error compared to earlier signal processing methods and could perform their measurements using a single A-Mode frame. Using the DNNs, two different machine learning pipelines have been proposed here to measure the elastic modulus; best among them could achieve an error of 9.3% with Pearson correlation coefficient of 0.94 (p < 0.001). The models were tested on Raspberry Pi and Jetson Nano single board computers to demonstrate real-time processing on low computational resources.