Remote plethysmographic imaging using ambient light.

Remote plethysmographic imaging using ambient light.

22 December 2008 | Wim Verkruijsse¹, Lars O Svaasand², and J Stuart Nelson¹
Remote photoplethysmography (PPG) using ambient light and a consumer-level digital camera is presented. The study demonstrates that PPG signals can be measured remotely (over 1 meter) using ambient light and a simple camera in movie mode. Heart rate (HR) and respiration rate (RR) can be quantified up to several harmonics. While the green channel shows the strongest PPG signal due to hemoglobin absorption, red and blue channels also contain PPG information. Results suggest that ambient light PPG may be useful for medical applications such as characterizing vascular skin lesions (e.g., port wine stains) and remote sensing of vital signs for triage or sports purposes. The study used a simple digital camera (Canon Powershot models A560, A570, A640) with ambient light as the illumination source. Movies were recorded of the facial area, and pixel values were averaged to improve signal-to-noise ratio (SNR). Spatial averaging was used to enhance SNR, and power and phase maps were generated. The results show that HR and RR can be measured with high accuracy, and that PPG signals can be used to characterize regions of high and low pulsatility on facial port wine stains (PWS). The study also demonstrates that phase information can be extracted from PPG signals. The results indicate that PPG signals can be used to detect HR and RR, and that PWS areas show distinct pulsatility compared to normal skin. The study also shows that PPG signals can be used to detect the propagation of cardiovascular waves, with the carotid artery possibly being imaged in one volunteer. The study highlights the potential of ambient light PPG for remote sensing of vital signs and characterization of vascular skin lesions. The results suggest that PPG signals can be used for a variety of applications, including triage and sports monitoring. The study also discusses the limitations of the current approach, including movement artifacts and reduced SNR due to CCD noise. Future research is needed to improve spatial resolution and accuracy of PPG imaging.Remote photoplethysmography (PPG) using ambient light and a consumer-level digital camera is presented. The study demonstrates that PPG signals can be measured remotely (over 1 meter) using ambient light and a simple camera in movie mode. Heart rate (HR) and respiration rate (RR) can be quantified up to several harmonics. While the green channel shows the strongest PPG signal due to hemoglobin absorption, red and blue channels also contain PPG information. Results suggest that ambient light PPG may be useful for medical applications such as characterizing vascular skin lesions (e.g., port wine stains) and remote sensing of vital signs for triage or sports purposes. The study used a simple digital camera (Canon Powershot models A560, A570, A640) with ambient light as the illumination source. Movies were recorded of the facial area, and pixel values were averaged to improve signal-to-noise ratio (SNR). Spatial averaging was used to enhance SNR, and power and phase maps were generated. The results show that HR and RR can be measured with high accuracy, and that PPG signals can be used to characterize regions of high and low pulsatility on facial port wine stains (PWS). The study also demonstrates that phase information can be extracted from PPG signals. The results indicate that PPG signals can be used to detect HR and RR, and that PWS areas show distinct pulsatility compared to normal skin. The study also shows that PPG signals can be used to detect the propagation of cardiovascular waves, with the carotid artery possibly being imaged in one volunteer. The study highlights the potential of ambient light PPG for remote sensing of vital signs and characterization of vascular skin lesions. The results suggest that PPG signals can be used for a variety of applications, including triage and sports monitoring. The study also discusses the limitations of the current approach, including movement artifacts and reduced SNR due to CCD noise. Future research is needed to improve spatial resolution and accuracy of PPG imaging.
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