Model-based Region of Interest Segmentation for Remote Photoplethysmography

Abstract

Remote photoplethysmography (rPPG) is a non-contact technique for measuring vital physiological signs, such as heart rate (HR) and respiratory rate (RR). HR is a medical index which is widely used in health monitoring and emotion detection applications. Therefore, HR measurement with rPPG methods offers a convenient and non-invasive method for these applications. The selection of Region Of Interest (ROI) is a critical first step of many rPPG techniques to obtain reliable pulse signals. The ROI should contain as many skin pixels as possible with a minimum of non-skin pixels. Moreover, it has been shown that rPPG signal is not distributed homogeneously on skin. Some skin regions contain more rPPG signal than others, mainly for physiological reasons. In this paper, we propose to explicitly favor areas where the information is more predominant using a spatially weighted average of skin pixels based on a trained model. The proposed method has been compared to several state of the art ROI segmentation methods using a public database, namely the UBFC-RPPG dataset (Bobbia et al., 2017). We have shown that this modification in how the spatial averaging of the ROI pixels is calculated can significantly increase the final performance of heart rate estimate.