METHOD AND APPARATUS FOR NON-CONTACT ESTIMATION OF PULSE TRANSMIT TIME

• US 20170262987A1
• Filed: 03/09/2016
• Published: 09/14/2017
• Est. Priority Date: 03/09/2016
• Status: Abandoned Application

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Gnanasambandam, Nathan, Mestha, Lalit K.
• Application Number:
  US15/065,548
• Publication Number:
  US 20170262987A1
• Time in Patent Office: Days
• CPC Class Codes: A61B 5/0077 Devices for viewing the surface of the body, e.g. camera, magnifying lens
• CPC Class Codes: A61B 5/02125 of pulse wave propagation time
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/6889 Rooms
• CPC Class Codes: A61B 5/7282 Event detection, e.g. detecting unique waveforms indicative of a medical condition A61B5/4094, A61B5/4818, A61B5/349, A61B5/0823 take precedence
• CPC Class Codes: G06T 2207/10016 Video; Image sequence
• CPC Class Codes: G06T 2207/20032 Median filtering
• CPC Class Codes: G06T 2207/30104 Vascular flow; Blood flow; Perfusion
• CPC Class Codes: G06T 7/0016 involving temporal comparison

Abstract

A method, non-transitory computer readable medium and apparatus for estimating a pulse transmit time (PTT) to calculate a blood pressure are disclosed. For example, the method includes receiving a series of video images over a period of time that includes a first location of an individual and a second location of the individual, calculating a first set of luminance values of the first location and a second set of luminance values of the second location, estimating the PTT based on an average time difference from consecutive peaks of the first set of luminance values and the second set of luminance values and transmitting the PTT to a blood pressure calculation device to calculate the blood pressure based on the PTT that is estimated.

Claims

1. A method for estimating a pulse transmit time (PTT) to calculate a blood pressure, comprising:

receiving, by a processor, a series of video images over a period of time that includes a first location of an individual and a second location of the individual;

calculating, by the processor, a first set of luminance values of the first location and a second set of luminance values of the second location;

estimating, by the processor, the PTT based on an average time difference from consecutive peaks of the first set of luminance values and the second set of luminance values; and

transmitting, by the processor, the PTT to a blood pressure calculation device to calculate the blood pressure based on the PTT that is estimated.

2. The method of claim 1, wherein the first location comprises a palm of the individual.

3. The method of claim 1, wherein the second location comprises a forehead of the individual.

4. The method of claim 1, wherein the series of video images comprise consecutive video images of a single video.

5. The method of claim 1, wherein the series of video images comprise non-consecutive video images from a plurality of videos.

6. The method of claim 1, wherein the calculating further comprises:

recording, by the processor, the first set of luminance values of a region of interest (ROI) of the first location over the period of time;

recording, by the processor, the second set of luminance values of a ROI of the second location over the period of time; and

identifying, by the processor, each peak in the first set of luminance values of the ROI of the first location and each peak in the second set of luminance values of the ROI of the second location.

7. The method of claim 6, wherein the first set of luminance values of the ROI of the first location and the second set of luminance values of the ROI of the second location comprise a cyclical component.

8. The method of claim 6, wherein the ROI of the first location comprises a first plurality of macro pixels and the ROI of the second location comprises a second plurality of macro pixels.

9. The method of claim 8, wherein the first set of luminance values of each macro pixel of the first plurality of macro pixels and the second set of luminance values of each macro pixel of the second plurality of macro pixels comprise a maximum luminance value of a pixel within a respective macro pixel.

10. The method of claim 9, further comprising:

applying, by the processor, an optimization function to the first set of luminance values of the each macro pixel of the first plurality of macro pixels and the second set of luminance values of the each macro pixel of the second plurality of macro pixels; and

applying, by the processor, a median filter of a pre-defined size to the first set of luminance values of the each macro pixel of the first plurality of macro pixels and the second set of luminance values of the each macro pixel of the second plurality of macro pixels after the optimization function is applied.

11. The method of claim 10, wherein the comparing is performed between a randomly selected pair of macro pixels comprising a first macro pixel of the first plurality of macro pixels and a second macro pixel of the second plurality of macro pixels.

12. The method of claim 11, wherein the PTT that is estimated is an average value of an average time difference from the consecutive peaks for each randomly selected pair of macro pixels of a plurality of randomly selected pair of macro pixels.

13. The method of claim 6, wherein a peak is identified when a luminance value is greater than a first threshold and is separated from an adjacent peak by an amount of time greater than a second threshold.

14. The method of claim 6, wherein the estimating further comprises:

aligning, by the processor, the first set of luminance values with the second set of luminance values such that the each peak in the first set of luminance values of the ROI of the first location leads the each peak in the second set of luminance values of the ROI of the second location.

15. A non-transitory computer-readable medium storing a plurality of instructions, which when executed by a processor, cause the processor to perform operations for estimating a pulse transmit time (PTT) to calculate a blood pressure, the operations comprising:

receiving a series of video images over a period of time that includes a first location of an individual and a second location of the individual;

calculating a first set of luminance values of the first location and a second set of luminance values of the second location;

estimating the PTT based on an average time difference from consecutive peaks of the first set of luminance values and the second set of luminance values; and

transmitting the PTT to a blood pressure calculation device to calculate the blood pressure based on the PTT that is estimated.

16. The non-transitory computer-readable medium of claim 15, wherein the calculating further comprises:

recording the first set of luminance values of a region of interest (ROI) of the first location over the period of time;

recording the second set of luminance values of a ROI of the second location over the period of time; and

identifying each peak in the first set of luminance values of the ROI of the first location and each peak in the second set of luminance values of the ROI of the second location.

17. The non-transitory computer-readable medium of claim 16, wherein the ROI of the first location comprises a first plurality of macro pixels and the ROI of the second location comprises a second plurality of macro pixels.

18. The non-transitory computer-readable medium of claim 17, wherein the first set of luminance values of each macro pixel of the first plurality of macro pixels and the second set of luminance values of each macro pixel of the second plurality of macro pixels comprise a maximum luminance value of a pixel within a respective macro pixel.

19. The non-transitory computer-readable medium of claim 18, further comprising:

applying an optimization function to the first set of luminance values of the each macro pixel of the first plurality of macro pixels and the second set of luminance values of the each macro pixel of the second plurality of macro pixels; and

applying a median filter of a pre-defined size to the first set of luminance values of the each macro pixel of the first plurality of macro pixels and the second set of luminance values of the each macro pixel of the second plurality of macro pixels after the optimization function is applied.

20. A method for estimating a pulse transmit time (PTT) to calculate a blood pressure, the method comprising:

receiving, by a processor, a first video over a period of time of a forehead of an individual and a second video of a palm of the individual;

identifying, by the processor, a forehead region of interest (ROI) comprising a first plurality of macro pixels in the first video of the forehead and a palm ROI comprising a second plurality of macro pixels in the second video of the palm;

determining, by the processor, forehead luminance values for each one of the first plurality of macro pixels over the time period and palm luminance values for each one of the second plurality of macro pixels over the period of time;

identifying, by the processor, peaks in the forehead luminance values and the palm luminance values;

pairing, by the processor, a macro pixel of the first plurality of macro pixels with a macro pixel of the second plurality of macro pixels to create a plurality of macro pixel pairs;

aligning, by the processor, the forehead luminance values with the palm luminance values of each one of the plurality of macro pixel pairs;

calculating, by the processor, for each one of the plurality of macro pixel pairs an average time difference between consecutive peaks, wherein the consecutive peaks comprise a peak of the forehead luminance values and an adjacent peak of the palm luminance values;

estimating, by the processor, the PTT based on an overall average of the average time difference calculated for each one of the plurality of macro pixel pairs; and

transmitting, by the processor, the PTT to a blood pressure calculation device to calculate the blood pressure based on the PTT that is estimated.