System and method for determining video-based pulse transit time with time-series signals

摘要

What is disclosed is a system and method for determining a subject of interest's arterial pulse transit time from time-varying source signals generated from video images. In one embodiment, a video imaging system is used to capture a time-varying source signal of a proximal and distal region of a subject of interest. The image frames are processed to isolate localized areas of a proximal and distal region of exposed skin of the subject. A time-series signal for each of the proximal and distal regions is extracted from the source video images. A phase angle is computed with respect to frequency for each of the time-series signals to produce respective phase v/s frequency curves for each region. Slopes within a selected cardiac frequency range are extracted from each of the phase curves and a difference is computed between the two slopes to obtain an arterial pulse transit time for the subject.

主权项

1. A method for determining an arterial pulse transit time between a proximal and distal region of a subject of interest from source video images acquired using a video imaging system, the method comprising:
receiving time-varying source images acquired over at least one channel of a video imaging system, said source images comprising video images captured of a proximal and distal region of an area of exposed skin of a subject of interest in which plethysmographic signals can be registered and at least one background region in which plethysmographic signals cannot be registered, and said proximal and distal regions and said background region being exposed to the same environmental factors; extracting, from said source images a first time-series signal for said proximal region and a second times series signal for said distal region and at least one background region time-series signal; subtracting said first time-series signal and said background region times-series signal to obtain environmentally compensated time-series signal for said proximal region; subtracting said second time-series signal and said background region times-series signal to obtain environmentally compensated time-series signal for said distal region; computing a first phase angle φ1(ω) with respect to frequency ω of said environmentally compensated time-series signal for said proximal region; computing a second phase angle φ2(ω) with respect to frequency ω of said environmentally compensated time-series signal for said distal region; plotting said computed phases with respect to frequency to obtain respective phase vs frequency curves for each of said proximal and distal regions; computing respective slopes T1=∂φ1/∂ω and T2=∂φ2/∂ω within a defined cardiac frequency range between 0.75 to 4.0 Hz from each of said respective phase vs frequency curves; computing a difference between said slopes T1 and T2, said difference comprising an arterial pulse transit time for said subject between said proximal and distal regions; and storing, using a processor, said arterial pulse transit time to a storage device.