Contactless multiple wavelength photoplethysmographic imaging: a first step toward "SpO2 camera" technology

Area of Science:

• Biomedical Optics
• Medical Imaging
• Physiological Monitoring

Background:

• Contactless monitoring of physiological parameters is crucial for advanced medical diagnostics.
• Assessing arterial oxygen saturation (SpO2) distribution non-invasively requires sophisticated imaging techniques.
• Optical plethysmography offers a promising avenue for remote physiological signal acquisition.

Purpose of the Study:

• To develop and validate a method for contactless, 2-D imaging of arterial oxygen saturation (SpO2) distribution.
• To explore the feasibility of using multi-wavelength optical plethysmography for remote SpO2 measurement.
• To investigate the potential of a CMOS camera system for capturing spatially resolved photoplethysmographic signals.

Main Methods:

• A monochrome CMOS camera with an apochromatic lens and a 3-wavelength LED ring light (660 nm, 810 nm, 940 nm) was employed.
• Video data were acquired at different frame rates, synchronized with ECG and respiration.
• Image processing involved dividing frames into Regions of Interest (ROIs) and analyzing time-resolved photoplethysmographic signals.

Main Results:

• Photoplethysmograms correlated well with respiration signals across all three wavelengths.
• Heartbeat-related pulsations were detected at multiple wavelengths, even at higher frame rates.
• Spatially resolved, heartbeat-related photoplethysmograms were successfully acquired using a remote camera system.

Conclusions:

• The study demonstrates the feasibility of non-contact, 2-D imaging reflection-mode pulse oximetry.
• This technique shows potential for mapping SpO2 distribution within tissues remotely.
• Further development is necessary for the clinical application of these non-contact imaging devices.