System and methods for measuring physiological parameters

• US 10,004,410 B2
• Filed: 12/19/2014
• Issued: 06/26/2018
• Est. Priority Date: 12/19/2013
• Status: Active Grant

• Current Assignee: Board of Trustees of The University of Illinois, University of North Carolina At Chapel Hill (University of North Carolina System)
• Original Assignee: Board of Trustees of The University of Illinois, University of North Carolina At Chapel Hill (University of North Carolina System)
• Inventors: Porges, Stephen W., Davila, Maria I., Lewis, Gregory F.
• Primary Examiner(s): Schaetzle, Kennedy
• Application Number:
  US15/105,674
• Publication Number:
  US 20160317041A1
• Time in Patent Office: 1,285 Days
• CPC Class Codes: A61B 2576/00 Medical imaging apparatus involving image processing or analysis A61B1/00009, A61B6/52 and A61B8/52 take precedence; image processing per se G06T; details of algorithms for analysing medical images G06T7/0012
• CPC Class Codes: A61B 5/002 Monitoring the patient using a local or closed circuit, e.g. in a room or building A61B5/0017 takes precedence
• CPC Class Codes: A61B 5/0037 Performing a preliminary scan, e.g. a prescan for identifying a region of interest
• CPC Class Codes: A61B 5/0077 Devices for viewing the surface of the body, e.g. camera, magnifying lens
• CPC Class Codes: A61B 5/024 Detecting, measuring or recording pulse rate or heart rate A61B5/0205, A61B5/021 take precedence
• CPC Class Codes: A61B 5/02405 Determining heart rate variability
• CPC Class Codes: A61B 5/08 Detecting, measuring or recording devices for evaluating the respiratory organs A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/14552 Details of sensors specially adapted therefor
• CPC Class Codes: A61B 5/7235 Details of waveform analysis A61B5/349 takes precedence

Abstract

The present invention relates generally to a system and methods for measuring physiological parameters. More specifically, the present invention relates to a noncontact technology by which one or more physiological parameters of a subject may be efficiently and quickly detected. Among other advantages, the present invention can be used to assess and monitor vital signs of one or more subjects in a variety of contexts including for medical or security triage purposes, for use in healthcare waiting rooms, as part of human imaging systems, or during surgery.

Claims

1. A computer method for determining one or more physiological parameters of a living subject comprising:

capturing by a capture device at least two images having a temporally sequential relationship of a region of interest (ROI) on a body surface of the living subject and generate digital signals for each of the at least two images as digital output;

a processing component processing the digital output for each of the at least two images comprising the steps of;

(a) capturing by the processing component the each of the at least two images as information on an analog-to-digital sensor that has been calibrated by the processing component, based upon the one or more physiological parameters, environmental context in which the living subject is positioned, and specifications of the capture device, to adjust information content in the digital output;

(b) receiving by the processing component and pre-processing the digital output from the each of the at least two images in real-time to select the ROI in the each of the at least two images individually;

(c) extracting by the processing component a pulse wave sample from the ROI for the each of the at least two images, the extracted pulse wave sample corresponding to a single time point represented by the each of the at least two images, the preprocessing including separating the digital output into red light data, green light data, and blue light data and calculating a ratio of red light data to green light data;

(d) combining by the processing component multiple color planes information, including at least one of hue, saturation, luminance, intensity, and value, with the red light, green light, and blue light data to modify the extracted pulse wave sample;

(e) generating by the processing component a second pulse wave sample by step (a), step (b), step (c) and step (d), or any subset thereof for the each of the at least two images;

(f) post-processing by the processing component the second pulse wave sample of step (e) to form a post-processed pulse wave; and

(g) determining by the processing component the physiological parameter of the subject from the post-processed pulse wave of step (f).

2. The computer method of claim 1 wherein the pre-processing includes at least one of masking to remove non-skin pixels and correcting for movement of the subject.

3. The computer method of claim 2, wherein the correcting for movement comprises using a ratio-based measure.

4. The computer method of claim 2, wherein the correcting for movement employs a pixel level correction, comprising:

(a) a series of one or more mathematical operations combining information from two or more color plane values for a given pixel;

(b) a series of one or more mathematical operations combining information from two or more adjacent pixels within a color plane;

or

(c) any combination of procedures (a) or (b).

5. The computer method of claim 2, wherein the masking is accomplished by creating a specific skin mask designed using a profile of the body surface based on hue, saturation, and/or luminance of the body surface and applying the skin mask to the each of the at least two images to remove non-skin pixels.

6. The computer method of claim 1, wherein the pre-processing includes pixel level correction to minimize impact of lighting.

7. The computer method of claim 1, wherein the post-processing comprises one or more of filtering, performing time series analysis, detrending, and curve fitting.

8. The computer method of claim 1, wherein the processing component extracts interbeat intervals from the arterial pulse wave.

9. The computer method of claim 8, wherein the processing component extracts from the interbeat intervals components of heart rate variability, including at least one of low frequency and respiratory sinus arrhythmia.

10. The computer method of claim 8, wherein the processing component extracts a respiration rate from the interbeat intervals.

11. A method for measuring physiological parameters of a human subject, the method comprising:

(a) capturing a temporal sequence of images from which a region of interest (ROI) identifiable on a body surface on the subject using a digital color video;

(b) preprocessing in real time the ROI in the each of the images individually, to extract a pulse signal from the ROI for the each of the images, each of the pulse signals corresponding to a single time point, said preprocessing including separating light into red, green, and blue light and calculating a ratio of red to green light;

(c) generating in real-time a pulse wave from the pulse signals obtained through step (b) for the each of the images;

(d) post-processing the pulse wave generated by step (c) to provide a post-processed pulse wave for the each of the images; and

(e) determining arterial blood pulse rate and amplitude of the subject from the post-processed pulse wave of step (d) for the each of the images.

12. The method of claim 11, wherein the body surface comprises a high capillary density.

13. The method of claim 11, wherein the pre-processing includes at least one of masking to remove non-skin pixels and correcting for movement of the skin surface.

14. The method of claim 13, wherein the correcting for movement comprises employing a ratio-based measure.

15. The method of claim 13, wherein said correcting for movement employs a pixel level correction.

16. The method of claim 11, wherein the pre-processing includes pixel level correction to minimize impact of lighting.

17. The method of claim 11, wherein the post-processing comprises one or more of filtering, performing time series analysis, detrending, and curve fitting.

18. The method of claim 11, further comprising extracting interbeat intervals from the pulse wave.

19. The method of claim 18, further comprising extracting from the interbeat intervals components of heart rate variability selected from low frequency and respiratory sinus arrhythmia.

20. The method of claim 18, further comprising extracting respiration rate from the interbeat intervals.

21. The method of claim 18, further comprising extracting beat to beat pulse amplitude.

22. A method for evaluating a human subject for stress response, the method comprising:

monitoring a physiological response of the subject according to claim 11;

exposing the subject to a challenge while continuing to monitor the physiological response; and

evaluating the physiological response before and after the challenge.

23. A computer method for determining one or more physiological parameters of a living subject comprising:

a capture device to capture images consisting of a first single image and a second single image having a temporally sequential relationship of a region of interest (ROI) on a body surface of the living subject and generate digital signals of the first single image and the second single image as digital output;

a processing component processing the digital output comprising the steps of;

(a) capturing by said processing component each of the first single image and the second single image as information on an analog-to-digital sensor that has been calibrated by said processing component, based upon the one or more physiological parameters, environmental context in which the living subject is positioned, and specifications of the capture device, to adjust information content in the digital output;

(b) receiving by said processing component and pre-processing the digital output from the each of the first single image and the second single image in real-time to select the ROI in the each of the at least two images individually;

(c) extracting by said processing component a pulse wave sample from the ROI for the each of the first single image and the second single image, the extracted pulse wave sample corresponding to a single time point represented by the each of the first single image and the second single image, the preprocessing including separating the digital output into red light data, green light data, and blue light data and calculating a ratio of red light data to green light data;

(d) combining by said processing component multiple color planes information, including at least one of hue, saturation, luminance, intensity, and value, with the red light, green light, and blue light data to modify the extracted pulse wave sample;

(e) generating by said processing component a second pulse wave sample by step (a), step (b), step (c) and step (d), or any subset thereof for the each of the first single image and the second single image;

(f) post-processing by said processing component the second pulse wave sample of step (e) to form a post-processed pulse wave; and

(g) determining by said processor the physiological parameter of the subject from the post-processed pulse wave of step (f).