Camera-Based Dual-Wavelength Defocused Speckle Imaging for Multi-Point Seismocardiographic Motion Measurement

Continuous monitoring of cardiac activity is crucial for detecting anomalies such as heart failure and coronary artery disease, and it can alleviate the burden of cardiovascular disease on healthcare systems. This study introduces a novel concept for contactless monitoring of multi-point cardiac motion using dual- wavelength defocused speckle imaging (DW-DSI). A prototype system was developed to measure multi-point seismocardiography (MP-SCG) signals from the atrial and ventricular regions. In addition, blood pressure (BP) monitoring was demonstrated as a proof of concept using the time delay between atrial and ventricular motion signals. An experiment involving 19 subjects with ice water stimulation protocol demonstrated that the performance of BP estimation using time delay features of MP-SCG is comparable to BP estimated from ECG-PPG derived pulse arrival time. The results showed that the best performance was achieved using the correlation features extracted from MP-SCG, such as time delay information and heart rate, in combination with an artificial neural network model. The mean absolute error for systolic/diastolic/mean BP are 6.954 mmHg, 5.368 mmHg and 5.415 mmHg, with Pearson correlation coefficient of 0.639, 0.559 and 0.517. This demonstrates the potential of the camera-based DW-DSI system for measuring MP-SCG and the feasibility towards continuous BP monitoring.