Contactless System and Method for Assessing Tissue Viability and Other Hemodynamic Parameters

Abstract

A contactless system for assessing tissue viability and other hemodynamic parameters includes one or more light sources configured to emit lights at a predetermined wavelength sensitive to hemoglobin concentration associated with spontaneous hemodynamic oscillations at tissue in a predetermined area of a human subject. One or more polarizers are each coupled to one or more of the one or more light sources and are configured to polarize the light to a polarized state such that the polarized light in the polarized state diffuses into the tissue in the predetermined area at a predetermined depth and the polarized light is maintained in the polarized state at the predetermined depth. One or more detectors each including a detector polarizer coupled thereto are configured to discriminate the light maintained in the polarized state and at the predetermined depth and are configured to generate a plurality of frames of the tissue in the predetermined area at the predetermined depth. A controller is coupled to the one or more light sources and the one or more detectors. The controller is configured to: acquire the plurality of frames, select a region of interest having the same coordinates for each of the plurality of frames, average the number of pixels within each region of interest to create a raw reference signal, detrend the raw reference signal to create a detrended raw reference signal, perform frequency domain analysis of the detrended raw reference signal, identify a frequency band of interest associated with the spontaneous hemodynamic oscillations, and perform an inverse fast Fourier transform within the frequency band of interest to generate a reference signal indicative of blood volume oscillations at a selected spontaneous hemodynamic oscillation. For each sample of the reference signal at a predetermined point in time, the controller multiplies the sample by each pixel of a frame at the same predetermined point in time to generate a three-dimensional coordinate matrix including a plurality of correlation matrix frames at each predetermined point in time. The controller adds the plurality of correlation matrix frames at each predetermined point in time to generate a two-dimensional hemodynamic map indicative of the strength of the spontaneous hemodynamic oscillation to assess the viability of the tissue in the predetermined area.

1 . A contactless system for assessing tissue viability and other hemodynamic parameters, the system comprising:
 one or more light sources configured to emit light at one or more predetermined wavelengths sensitive to concentration of hemoglobin or other chromophores associated with spontaneous hemodynamic oscillations into tissue and/or blood at a predetermined area of a human subject;   one or more polarizers each coupled to one or more of the one or more light sources configured to polarize the light to a polarized state such that the polarized light in the polarized state diffuses into the tissue in the predetermined area at a predetermined depth range and the polarized light is maintained in the polarized state at the predetermined depth range;   one or more detectors each including a detector polarizer coupled thereto configured to discriminate the light maintained in the polarized state and at the predetermined depth range from polarized light reflected from the tissue and/or blood in the predetermined area which has not been maintained in the polarized state and configured to generate a plurality of frames of the tissue in the predetermined area at the predetermined depth; and   a controller coupled to the one or more light sources and the one or more detectors configured to acquire the plurality of frames and configured to detect time-varying changes in the concentration of the hemoglobin or other chromophores resulting from the spontaneous hemodynamic oscillations in the predetermined area using the discriminated light maintained in the polarized state and at the predetermined depth range.   
     
     
         2 . The system of  claim 1  in which the controller is configured to generate a two-dimensional hemodynamic map indicative of the strength of the spontaneous hemodynamic oscillation to further assess the viability of the tissue and/or the other hemodynamic parameters. 
     
     
         3 . The system of  claim 2  in which the controller is configured to perform one or more or all of the following:
 select a region of interest having the same coordinates for each of the plurality of frames; 
 average the number of pixels within each region of interest to create a raw reference signal; 
 detrend the raw reference signal to create a detrended raw reference signal; 
 perform frequency domain analysis of the detrended raw reference signal; 
 identify a frequency band of interest associated with the spontaneous hemodynamic oscillation; 
 perform an inverse fast Fourier transform within the frequency band of interest to generate a reference signal including a plurality of samples and indicative of blood volume oscillations at a selected spontaneous hemodynamic oscillation; 
 for each sample of the reference signal at a predetermined point in time, multiply the sample by each pixel of a frame at the same predetermined point in time to generate a three-dimensional coordinate matrix including a plurality of correlation matrix frames at each predetermined point in time; and 
 add the plurality of correlation matrix frames at each predetermined point in time to generate a two-dimensional hemodynamic map indicative of the strength of the spontaneous hemodynamic oscillation to assess the viability of the tissue and/or the other hemodynamic parameters in the predetermined area. 
 
     
     
         4 . The system of  claim 1  in which the spontaneous hemodynamic oscillations have a frequency in the range of 0.05 Hz to about 1.5 Hz. 
     
     
         5 . The system of  claim 1  in which the predetermined wavelength is in the range of about 500 nm to about 1,000 nm. 
     
     
         6 . The system of  claim 1  in which the predetermined depth is in the range of about 0.1 mm to about 0.5 mm. 
     
     
         7 . The system of  claim 1  in which the other hemodynamic parameters include at least one of: a heart rate, a resting heart rate, heart rate variability, or tissue and/or blood saturation. 
     
     
         8 . The system of  claim 1  in which the one or more detectors include a CCD camera. 
     
     
         9 . The system of  claim 1  in which the one or more detectors include a CMOS camera. 
     
     
         10 . The system of  claim 1  in which the predetermined area includes a burn area of the human subject. 
     
     
         11 . The system of  claim 1  in which the predetermined area includes a wound area of a human subject. 
     
     
         12 . The system of  claim 1  further including a light filtering lens coupled to one or more light sources. 
     
     
         13 . A contactless method for assessing tissue viability and other hemodynamic parameters, the method comprising:
 emitting light at one or more predetermined wavelength sensitive to concentration of hemoglobin or other chromophores associated with spontaneous hemodynamic oscillations into tissue and/or blood at a predetermined area of a human subject;   polarizing the light to a polarized state such that the polarized light in the polarized state diffuses into the tissue in the predetermined area at a predetermined depth range and the polarized light is maintained in the polarized state at the polarized depth range;   discriminating the light maintained in the polarized state and at the predetermined depth range from polarized light reflected from the tissue in the predetermined area which has not been maintained in the polarized state and generating a plurality of frames of the tissue in the predetermined area at the predetermined depth range; and   acquiring the plurality of frames to detect time varying changes in the concentration of the hemoglobin or other chromophores resulting from the spontaneous hemodynamic oscillations in the predetermined area using the discriminated light maintained in the polarized state and at the predetermined depth range.   
     
     
         14 . The method of  claim 13  further including generating a two-dimensional hemodynamic map indicative of the strength of the spontaneous hemodynamic oscillation to further assess the viability of the tissue and/or the other hemodynamic parameters in the predetermined area. 
     
     
         15 . The method of  claim 14  further including performing one or more or all of the following:
 acquiring the plurality of frames; 
 selecting a region of interest having the same coordinates for each of the plurality of frames; 
 averaging the number of pixels within each region of interest to create a raw reference signal; 
 detrending the raw reference signal to create a detrended raw reference signal; 
 performing frequency domain analysis of the detrended raw reference signal; 
 identifying a frequency band of interest associated with the spontaneous hemodynamic oscillations; 
 performing an inverse fast Fourier transform within the frequency band of interest to generate a reference signal including a plurality of samples and indicative of blood volume oscillations at a selected spontaneous hemodynamic oscillation; 
 for each sample of the reference signal at a predetermined point in time, multiplying the sample by each pixel of a frame at the same predetermined point in time to generate a three-dimensional coordinate matrix including a plurality of correlation matrix frames at each predetermined point in time; and/or 
 adding the plurality of correlation matrix frames at each predetermined point in time to generate a two-dimensional hemodynamic map indicative of the strength of the spontaneous hemodynamic oscillation to assess the viability of the tissue and/or the other hemodynamic parameters in the predetermined area. 
 
     
     
         16 . The method of  claim 13  in which the other hemodynamic parameters include least one of: a heart rate, a resting heart rate, heart rate variability, or tissue saturation. 
     
     
         17 . The method of  claim 13  in which the spontaneous hemodynamic oscillations have a frequency in the range of 0.05 Hz to about 1.5 Hz. 
     
     
         18 . The method of  claim 13  in which the predetermined wavelength is in the range of about 500 nm to about 1,000 nm. 
     
     
         19 . The method of  claim 13  in which the predetermined depth is in the range of about 0.1 mm to about 0.5 mm. 
     
     
         20 . The method of  claim 13  in which the predetermined area includes a burn area of the human subject. 
     
     
         21 . The method of  claim 13  in which the predetermined area includes a wound area of a human subject.