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Feasibility of long-distance heart rate monitoring using transmittance photoplethysmographic imaging (PPGI).

Amelard R, Scharfenberger C, Kazemzadeh F, Pfisterer KJ, Lin BS, Clausi DA, Wong A - Sci Rep (2015)

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: University of Waterloo, Department of Systems Design Engineering, Waterloo, N2L3G1, Canada.

ABSTRACT
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.

No MeSH data available.


Overview of the processing steps for the proposed PPGI system.Upon acquiring frames, ambient correction using TCI is performed, which removes temporal changes in ambient illumination from the frames. This is followed by denoising to remove camera sensor noise and process noise from the light-tissue interaction, and smooth motion detrending. The resulting signal is an extracted stable PPGI signal.
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f2: Overview of the processing steps for the proposed PPGI system.Upon acquiring frames, ambient correction using TCI is performed, which removes temporal changes in ambient illumination from the frames. This is followed by denoising to remove camera sensor noise and process noise from the light-tissue interaction, and smooth motion detrending. The resulting signal is an extracted stable PPGI signal.

Mentions: This paper presents a pilot study to assess the feasibility of long-distance cardiovascular monitoring using transmittance PPGI. For this purpose, a novel non-contact transmittance PPGI system is proposed which is able to monitor cardiovascular activity remotely by correcting for ambient lighting fluctuations and extracting the subtle blood pulse signal using signal processing tools. This system comprises a 100 fps camera, a high-powered LED (655 nm), a microcontroller to synchronise frame captures and illumination, and image and signal processing software on a computer. Figure 1 shows a graphical representation of this system, and Figure 2 shows the processing steps. Temporally coded illumination (TCI) is introduced to remove ambient lighting artefacts at the acquisition level, thus correcting the data prior to further processing, similar to that introduced in our previous work18. The proposed PPGI system used for this study extends substantially beyond our previously reported work by incorporating a comprehensive set of signal processing steps, a larger testing sample size, and more rigorous statistical and qualitative analysis. The signal processing is particularly important for this study, as long-distance cardiovascular monitoring scenarios result in acquired signals with low signal-to-noise ratios (SNR).


Feasibility of long-distance heart rate monitoring using transmittance photoplethysmographic imaging (PPGI).

Amelard R, Scharfenberger C, Kazemzadeh F, Pfisterer KJ, Lin BS, Clausi DA, Wong A - Sci Rep (2015)

Overview of the processing steps for the proposed PPGI system.Upon acquiring frames, ambient correction using TCI is performed, which removes temporal changes in ambient illumination from the frames. This is followed by denoising to remove camera sensor noise and process noise from the light-tissue interaction, and smooth motion detrending. The resulting signal is an extracted stable PPGI signal.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4594125&req=5

f2: Overview of the processing steps for the proposed PPGI system.Upon acquiring frames, ambient correction using TCI is performed, which removes temporal changes in ambient illumination from the frames. This is followed by denoising to remove camera sensor noise and process noise from the light-tissue interaction, and smooth motion detrending. The resulting signal is an extracted stable PPGI signal.
Mentions: This paper presents a pilot study to assess the feasibility of long-distance cardiovascular monitoring using transmittance PPGI. For this purpose, a novel non-contact transmittance PPGI system is proposed which is able to monitor cardiovascular activity remotely by correcting for ambient lighting fluctuations and extracting the subtle blood pulse signal using signal processing tools. This system comprises a 100 fps camera, a high-powered LED (655 nm), a microcontroller to synchronise frame captures and illumination, and image and signal processing software on a computer. Figure 1 shows a graphical representation of this system, and Figure 2 shows the processing steps. Temporally coded illumination (TCI) is introduced to remove ambient lighting artefacts at the acquisition level, thus correcting the data prior to further processing, similar to that introduced in our previous work18. The proposed PPGI system used for this study extends substantially beyond our previously reported work by incorporating a comprehensive set of signal processing steps, a larger testing sample size, and more rigorous statistical and qualitative analysis. The signal processing is particularly important for this study, as long-distance cardiovascular monitoring scenarios result in acquired signals with low signal-to-noise ratios (SNR).

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: University of Waterloo, Department of Systems Design Engineering, Waterloo, N2L3G1, Canada.

ABSTRACT
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.

No MeSH data available.