Non-Contact Assessment of Cardiovascular Function using a Multi-Camera Array

Abstract

A system and method are provided for non-contact cardiac assessment of a subject. Images of the subject are captured from at least two synchronized independent imaging devices spaced equidistant from the subject and positioned such that each imaging device captures an image of the subject different from other imaging devices. Spectral components of the captured images are extracted. The extracted spectral components are analyzed. A signal corresponding to cardiac information is identified in the extracted spectral components. The identified signal corresponding to the cardiac information is extracted from the extracted spectral components.

What is claimed is: 
     
         1 . A method for non-contact cardiac assessment of a subject, the method comprising:
 capturing images of the subject from at least two synchronized independent imaging devices spaced equidistant from the subject and positioned such that each imaging device captures an image of the subject different from other imaging devices;   extracting spectral components of the captured images;   analyzing the extracted spectral components;   identifying a signal in the extracted spectral components corresponding to cardiac information; and   extracting the signal in the extracted spectral components corresponding to the cardiac information.   
     
     
         2 . The method of  claim 1 , wherein capturing the images of the subject from at least two synchronized independent imaging devices comprises:
 capturing images of a head and neck of the subject from the at least two synchronized independent imaging devices.   
     
     
         3 . The method of  claim 1 , wherein extracting spectral components of the captured images comprises:
 extracting Red, Green, and Blue components of the captured images.   
     
     
         4 . The method of  claim 1 , wherein analyzing the extracted spectral components comprises:
 performing an independent component analysis on the extracted spectral components.   
     
     
         5 . The method of  claim 1 , wherein identifying a signal in the extracted spectral components corresponding to cardiac information comprises:
 bandpass filtering the extracted spectral components between about 0.3 Hz and about 6 Hz;   upsampling the extracted spectral components about 1200 Hz using cubic spline interpolation; and   choosing a signal from the extracted spectral components based on an estimate of signal-to-noise ratio (SNR) in an expected frequency range of a ncPPG component signal.   
     
     
         6 . The method of  claim 5 , wherein the expected frequency range of an ncPPG component signal is about 0.75 Hz to about 4 Hz. 
     
     
         7 . The method of  claim 1 , wherein extracting the signal in the extracted spectral components corresponding to the cardiac information comprises:
 transforming band power estimate to relative power by dividing by component signal power outside a peak frequency range but within about 0.75 Hz top about 4 Hz; and   extracting an independent component with a highest relative power.   
     
     
         8 . The method of  claim 7 , further comprising:
 segmenting the extracted component into five non-overlapping windows; and   finding a frequency with a highest power density in a probable pulse rate range and converting this frequency to beats per minute by 60·f max ,   wherein f max  is the frequency with the highest power density.   
     
     
         9 . A system for non-contact cardiac assessment of a subject, the system comprising:
 at least two imaging devices configured to individually capture images of the subject, the imaging devices being spaced equidistant from the subject and positioned such that each imaging device captures an image of the subject different from other imaging devices;   a data acquisition card in electrical communication with the at least two imaging devices; and   at least one computer in electrical communication with the at least two imaging devices and configured to:
 receive captured images from the at least two imaging devices; 
 extract spectral components of the captured images; 
 analyze the extracted spectral components; 
 identify a signal in the extracted spectral components corresponding to cardiac information; and 
 extract the signal in the extracted spectral components corresponding to the cardiac information, 
   wherein trigger signals generated by the data acquisition card cause images to be captured simultaneously by the at least two imaging devices and sent to the computer.   
     
     
         10 . The system of  claim 9 , wherein the subject is positioned at a distance of about 68 inches from the at least two imaging devices. 
     
     
         11 . The system of  claim 9 , wherein the system comprises three imaging devices about 20 degrees apart, spanning about 40 degrees of visibility of the subject. 
     
     
         12 . The system of  claim 9 , wherein the system comprises five imaging devices about 30 degrees apart, spanning about 120 degrees of visibility of the subject. 
     
     
         13 . The system of  claim 9 , wherein the system comprises nine imaging devices about 20 degrees apart, spanning about 160 degrees of visibility of the subject. 
     
     
         14 . The system of  claim 13 , further comprising:
 at least two lights positioned beyond imaging devices positioned at about ±80 degrees.   
     
     
         15 . The system of  claim 9 , wherein the system comprises four imaging devices about 40 degrees apart, spanning about 120 degrees of visibility of the subject. 
     
     
         16 . The system of  claim 9 , wherein the at least two imaging devices are positioned at a height to captures images of a head and neck of the subject. 
     
     
         17 . The system of  claim 9 , wherein the at least two imaging devices positioned along a semi-circle. 
     
     
         18 . The system of  claim 9 , further comprising:
 at least two lights sources, each light source corresponding to one of the at least two imaging device,   wherein the light sources are mounted above the at least two imaging devices.   
     
     
         19 . The system of  claim 18 , wherein the at least two light sources are mounted approximately 18 inches above the at least two imaging devices. 
     
     
         20 . The system of  claim 9 , wherein the at least two imaging devices are visible spectrum imaging devices.