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Selecting a region of interest for extracting physiological parameters from a video of a subject

  • US 9,986,923 B2
  • Filed: 01/09/2015
  • Issued: 06/05/2018
  • Est. Priority Date: 01/09/2015
  • Status: Active Grant
First Claim
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1. A system for selecting a region of exposed skin to extract at least one physiological parameter from a video of a subject, the system comprising:

  • a single band video camera with a bandpass filter for acquiring video of the subject, the video comprising a plurality of time-sequential image frames of an area of exposed skin of the subject, each of the time-sequential image frames comprising a plurality of pixels, the bandpass filter having a pass band in a wavelength range of 495-565 nm and/or 800-1000 nm; and

    a processor executing machine readable instructions which configure the processor to;

    analyze the time-sequential image frames to identify a plurality of regions of exposed skin of the subject where a plethysmographic signal can be detected;

    for each of the plurality of regions of exposed skin;

    process the pixels to obtain an associated time-series signal corresponding to relative blood volume changes in blood vessels close to a surface of the exposed skin within the region of interest;

    for each of the obtained time-series signals;

    compute a power spectral density of the time-series signal;

    identify a dominant frequency;

    identify harmonic frequencies of the dominant frequency;

    define a window of frequencies about the dominant frequency, frequencies within the window collectively defining a band of interest; and

    calculate a signal strength for the time-series signal over the band of interest;

    determine which of the time-series signals has a highest signal strength;

    select, automatically, one of the plurality of regions of exposed skin of the subject associated with the time-series signals having the highest signal strength; and

    extract at least one physiological parameter from the selected one of the plurality of regions of exposed skin.

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