Amelard Robert, Scharfenberger Christian, Kazemzadeh Farnoud, Pfisterer Kaylen J, Lin Bill S, Clausi David A, Wong Alexander
University of Waterloo, Department of Systems Design Engineering, Waterloo, N2L3G1, Canada.
University of Waterloo, Department of Kinesiology, Waterloo, N2L3G1, Canada.
Sci Rep. 2015 Oct 6;5:14637. doi: 10.1038/srep14637.
Photoplethysmography (PPG) devices are widely used for monitoring cardiovascular function. However, these devices require skin contact, which restricts their use to at-rest short-term monitoring. Photoplethysmographic imaging (PPGI) has been recently proposed as a non-contact monitoring alternative by measuring blood pulse signals across a spatial region of interest. Existing systems operate in reflectance mode, many of which are limited to short-distance monitoring and are prone to temporal changes in ambient illumination. This paper is the first study to investigate the feasibility of long-distance non-contact cardiovascular monitoring at the supermeter level using transmittance PPGI. For this purpose, a novel PPGI system was designed at the hardware and software level. Temporally coded illumination (TCI) is proposed for ambient correction, and a signal processing pipeline is proposed for PPGI signal extraction. Experimental results show that the processing steps yielded a substantially more pulsatile PPGI signal than the raw acquired signal, resulting in statistically significant increases in correlation to ground-truth PPG in both short- and long-distance monitoring. The results support the hypothesis that long-distance heart rate monitoring is feasible using transmittance PPGI, allowing for new possibilities of monitoring cardiovascular function in a non-contact manner.
光电容积脉搏波描记法（PPG）设备被广泛用于监测心血管功能。然而，这些设备需要与皮肤接触，这限制了它们仅用于静息状态下的短期监测。最近，光电容积脉搏波成像（PPGI）被提出作为一种非接触式监测方法，通过测量感兴趣空间区域内的血脉冲信号来实现。现有的系统工作在反射模式，其中许多系统仅限于短距离监测，并且容易受到环境光照的时间变化影响。本文是第一项研究使用透射式PPGI在超米级水平进行长距离非接触式心血管监测可行性的研究。为此，在硬件和软件层面设计了一种新型的PPGI系统。提出了时间编码照明（TCI）用于环境校正，并提出了一种信号处理流程用于提取PPGI信号。实验结果表明，与原始采集信号相比，这些处理步骤产生的PPGI信号搏动性更强，在短距离和长距离监测中与地面真值PPG的相关性均有统计学意义的显著提高。结果支持了使用透射式PPGI进行长距离心率监测是可行的这一假设，为以非接触方式监测心血管功能带来了新的可能性。
