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.

Description

RELATED APPLICATIONS

This application in
where FRAME_i is each individual pixels in specific frame at time i, e.g., t₁, t₂, t₃, . . . t_N, and R_Si is a sample at time i of the Reference Signal, e.g., t₁, t₂, t₃, . . . t_N.

Controller 50 then adds the plurality of correlation matrix frames 74 at each predetermined point in time to generate two-dimensional hemodynamic map 100, FIG. 4, indicative of the strength of spontaneous hemodynamic oscillations to assess the viability of tissue 16 in predetermined area 18. In one example, equation (3) below is used to generate two-dimensional hemodynamic map 100:

$\begin{array}{cc}{\sum }_{i=1}^N\mathrm{CMx}& \left(3\right)\end{array}$
where i is correlation matrix at time, i, e.g., t₁, t₂, t₃, . . . t_N. N is the total amount of is acquired frames, and CMx is the hemodynamic map showing areas of viable tissue.

In one design, system 10, FIG. 1, preferably includes display device 102 coupled electronically or wirelessly to controller 50, e.g., a computer monitor, a smart phone, a tablet, or similarly type device, which displays two-dimensional hemodynamic map 100.

The result is system 10 provides hemodynamic map 100, FIGS. 1 and 2, of tissue 16 in predetermined area 18 and at a depth of about 0.1 mm to about 0.5 mm needed for real-time assessment of the viability of tissue 16 in predetermined area 18 or other hemodynamic parameters, e.g., heart rate, resting heart rate, heart rate variability, tissue saturation for patients suffering from diminished blood circulation, and the like. In one design, system 10 provides hemodynamic map 100 which shows viable and necrotic tissue areas. If hemodynamic oscillations are detected and shown on hemodynamic map 100, e.g. indicated at 106 in caption 108, or shown in FIG. 4, the tissue is viable. If hemodynamic oscillations are not shown, and therefore not detected by the procedure described above, on hemodynamic map 100, the tissue is necrotic, e.g., indicated at 108, FIGS. 1 and 4.

Hemodynamic map 100, FIGS. 2 and 4, preferably has a maximum field of view (FOV) of tissue 16 in predetermined area 18 where tissue viability needs to be determined. In one design, the FOV, e.g., FOV-104, FIG. 1, displayed on display device 102 provides a real-time view of tissue 16 in predetermined area 18 needed for real-time assessment of tissue viability in an objective manner. In one example, FOV-104 of tissue 16 in predetermined area 18 may be about 10 inches by 10 inches. In other examples, FOV-104 of tissue 16 in predetermined area 18 may be larger or smaller than 10 inches by 10 inches as needed.

Controller 50, FIGS. 1 and 2, is also preferably configured to store data associated with one or more hemodynamic maps 100 created by controller 100 in storage device 110. Storage device 110 may include any combination of computer-readable media or memory. The computer-readable media or memory may be a computer-readable signal medium or a computer-readable storage medium. A computer-readable storage medium or memory may be, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. Other examples may include an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. As disclosed herein, the computer-readable storage medium or memory may be any tangible medium that can contain, or store one or more programs for use by or in connection with one or more processors on a computing device such as a computer, a tablet, a cell phone, a smart device, or similar type device. Controller 50 may also be configured to compress the data associated with the hemodynamic maps.

To reduce and minimize the impact of uncontrolled ambient light changes, system 10 and the method thereof may implement spectral estimation techniques of the ambient illumination to remove uncontrolled ambient light changes. In other designs, system 10 and the method thereof may remove ambient lighting artifacts at the acquisition level by removing temporal changes in ambient illumination measured during programmed periods of non-active tissue illumination.

System 10 also preferably includes user interface 112 coupled to controller 50 electronically or wirelessly which may allow a user of system 10 to visualize and interact with the stored or real-time data. Data may be retrieved from controller 50 and storage device 110 via a data jack or by wireless communication, as known by those skilled in the art. System 10 also includes power supply 116 configured to provide power to one or more light sources 12, one or more detectors 20, controller 50, and/or display device 102. In one design, power supply 116 may include batteries for portable applications.

In other designs, contactless system 10 and method for assessing tissue viability and other hemodynamic parameters may be a standalone device for operation room, a portable device, or integrated into wearable tools wore by medical personnel.

One example of the method for assessing tissue viability and other hemodynamic parameters includes emitting light at a predetermined wavelength sensitive to hemoglobin concentration associated with spontaneous hemodynamic oscillations at tissue in a predetermined area of a human subject, step 150, FIG. 6. The method also includes 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 such that the polarized light is maintained in the polarized state at the polarized depth, step 152. The method also includes discriminating the light maintained in the polarized state and at the predetermined depth and generating a plurality of frames of the tissue in the predetermined area at the predetermined depth, step 154. A plurality of frames are then acquired, step 156. A region of interest is then selected having the same coordinates for each of the plurality of frames, step 158. The number of pixels within each region of interest is averaged to create a raw reference signal, step 160. The raw reference signal is detrended to create a detrended raw reference signal, step 162. Frequency domain analysis is performed of the detrended raw reference signal, step 168. A frequency band of interest is identified associated with the spontaneous hemodynamic oscillations, step 170. An inverse fast Fourier transform (iFFT) is performed within the frequency band of interest to generate a raw reference signal indicative of blood volume oscillations at a selected spontaneous hemodynamic oscillation, step 172. For each sample of the raw reference signal at a predetermined point in time, the sample is multiplied 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, step 174. The plurality of correlation matrix frames at each predetermined point in time are added to generate a two-dimensional hemodynamic map indicative of the strength of the spontaneous hemodynamic oscillations to assess the viability of tissue in the predetermined area or assess the viability of other hemodynamic parameters, step 176.

The result is system 10 and the method thereof provides a contactless real-time assessment of tissue viability and other hemodynamic parameters that allows a user to quantitatively assess the tissue health to provide objective metrics to support and guide accurate tissue excision of a burn wound or similar type wound. System 10 and the method thereof allows clinicians to selecting a level of debridement of a burn wound at a desired depth to minimize inflammation and determine the optimal treatment and remove virtually all the necrotic tissue in the burn wound or similar type wound in a time efficient manner. System 10 and the method thereof eliminates the need for intrusive tissue contact and preferably provides for long distance tissue viability assessment monitoring when compared to more conventional invasive imaging systems and methods discussed in the Background section. System 10 and the method thereof may provide opportunities in settings where multi-individual assessment may be extremely difficult or not feasible, such as intensive care units, emergency rooms, or where the condition of the patient may not allow for contact measurements.

One advantage of system 10 and the method thereof relying on spontaneous hemodynamic oscillation measurements discussed above with reference to one or more of FIG. 1-6, rather than absolute concentration measurements of chromophores present in the cardiovascular system, is an optical path length factor approximation is not required by system 10 and the method thereof. This may eliminate the need to rely on estimation errors. System 10 and method thereof, unlike conventional near infrared spectroscopy (NIRS) techniques, preferably does not require absolute concentration retrieval of the chromophores present in the cardiovascular system of tissue 16 of predetermined area 18 of human subject 16. Instead, system 10 and the method thereof preferably utilizes controller 50, one or more light sources 12, and one or more detectors 20. In one example.

For enablement purposes only, the following code portions are provided which can be executed on one or more processor, a computing device, or computer to carry out the primary steps and/or functions of contactless system 10 and method for assessing tissue viability and other hemodynamic parameters discussed above with reference to one or more of FIGS. 1-6. Other equivalent algorithms and code can be designed by a software engineer and/or programmer skilled in the art using the information provided herein.

%Acquire image
Frame = get frame (n,m) from camera/sensors etc.
%Determine ROI (region of interest)
maskmother = zeros(n,m) %set to zero a matrix equal to the size of the acquired
image
% Set to 1 an area of interest where reference signal will be calculated from
mask_1 = ones (maskmother (n,m) )
%Average pixels within selected ROI:
im = Frame.* mask_1
%Detrend im signal
im = im − im_Trend
%identify frequency components in im signal by FFT (Fast Fourier Transform)
PSD = FFT (im)
%Extrapolate Reference Signal by performing Inverse Fourier Transform only
between frequency range of interest (for example HR, respiration rate etc.).
Discard imaginary part
Ref = Real [FFT−1( PSD(C1<f<C2) )]
%Integrate reference signal and acquired images product over time to obtain
hemodynamic map (S):
S = sumt (Ref.*Frame)

Although specific features of the invention are shown in some drawings and not in others, this is for convenience only as each feature may be combined with any or all of the other features in accordance with the invention. The words “including”, “comprising”, “having”, and “with” as used herein are to be interpreted broadly and comprehensively and are not limited to any physical interconnection. Moreover, any embodiments disclosed in the subject application are not to be taken as the only possible embodiments.

In addition, any amendment presented during the prosecution of the patent application for this patent is not a disclaimer of any claim element presented in the application as filed: those skilled in the art cannot reasonably be expected to draft a claim that would literally encompass all possible equivalents, many equivalents will be unforeseeable at the time of the amendment and are beyond a fair interpretation of what is to be surrendered (if anything), the rationale underlying the amendment may bear no more than a tangential relation to many equivalents, and/or there are many other reasons the applicants cannot be expected to describe certain insubstantial substitutes for any claim element amended.

Other embodiments will occur to those skilled in the art and are within the following claims.

Claims

1. A contactless system for assessing tissue viability and other hemodynamic parameters, the system comprising:

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 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 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 configured to discriminate the light maintained in the polarized state and at the predetermined depth 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, the controller 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,

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.

2. 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.

3. The system of claim 1 in which the predetermined wavelength is in the range of about 500 nm to about 1,000 nm.

4. The system of claim 1 in which the predetermined depth is in the range of about 0.1 mm to about 0.5 mm.

5. The system of claim 1 in which the other hemodynamic parameters include one or more of: heart rate, resting heart rate, heart rate variability, and tissue saturation for patients suffering from diminished blood circulation.

6. The system of claim 1 in which the one or more detectors include a CCD camera.

7. The system of claim 1 in which the one or more detectors include a CMOS camera.

8. The system of claim 1 in which the predetermined area includes a burn area of the human subject.

9. The system of claim 1 in which the predetermined area includes a wound area of a human subject.

10. The system of claim 1 further including a light filtering lens coupled to one or more light sources.

11. A contactless method for assessing tissue viability and other hemodynamic parameters, the method comprising:

emitting light at a predetermined wavelength sensitive to hemoglobin concentration associated with spontaneous hemodynamic oscillations at tissue in 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 and the polarized light is maintained in the polarized state at the polarized depth;

discriminating the light maintained in the polarized state and at the predetermined depth and generating a plurality of frames of the tissue in the predetermined area at the predetermined depth;

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

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.

12. The method of claim 11 in which 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 assess the viability of other hemodynamic parameters including one or more of: heart rate, resting heart rate, heart rate variability, and tissue saturation for patients suffering from diminished blood circulation.

13. The method of claim 11 in which the spontaneous hemodynamic oscillations have a frequency in the range of 0.05 Hz to about 1.5 Hz.

14. The method of claim 11 in which the predetermined wavelength is in the range of about 500 nm to about 1,000 nm.

15. The method of claim 11 in which the predetermined depth is in the range of about 0.1 mm to about 0.5 mm.

16. The method of claim 11 in which the predetermined area includes a burn area of the human subject.

17. The method of claim 11 in which the predetermined area includes a wound area of a human subject.

18. A contactless system for assessing tissue viability and other hemodynamic parameters, the system comprising:

one or more light sources configured to emit lights at a predetermined wavelength sensitive to hemoglobin concentration associated with spontaneous hemodynamic oscillations into tissue 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 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 assess the viability of the tissue and/or the other hemodynamic parameters in the predetermined area using the discriminated light maintained in the polarized state and at the predetermined depth range.

19. The system of claim 18 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.

20. The system of claim 18 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.

21. The system of claim 18 in which the spontaneous hemodynamic oscillations have a frequency in the range of 0.05 Hz to about 1.5 Hz.

22. The system of claim 18 in which the predetermined wavelength is in the range of about 500 nm to about 1,000 nm.

23. The system of claim 18 in which the predetermined depth is in the range of about 0.1 mm to about 0.5 mm.

24. The system of claim 18 in which the other hemodynamic parameters include one or more of: heart rate, resting heart rate, heart rate variability, and tissue saturation for patients suffering from diminished blood circulation.

25. The system of claim 18 in which the one or more detectors include a CCD camera.

26. The system of claim 18 in which the one or more detectors include a CMOS camera.

27. The system of claim 18 in which the predetermined area includes a burn area of the human subject.

28. The system of claim 18 in which the predetermined area includes a wound area of a human subject.

29. The system of claim 18 further including a light filtering lens coupled to one or more light sources.

30. A contactless method for assessing tissue viability and other hemodynamic parameters, the method comprising:

emitting light at a predetermined wavelength sensitive to hemoglobin concentration associated with spontaneous hemodynamic oscillations into tissue 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 assess the viability of the tissue and/or the other hemodynamic parameters in the predetermined area using the discriminated light maintained in the polarized state and at the predetermined depth range.

31. The method of claim 30 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.

32. The method of claim 30 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.

33. The method of claim 30 in which the other hemodynamic parameters include one or more of: heart rate, resting heart rate, heart rate variability, and tissue saturation for patients suffering from diminished blood circulation.

34. The method of claim 30 in which the spontaneous hemodynamic oscillations have a frequency in the range of 0.05 Hz to about 1.5 Hz.

35. The method of claim 30 in which the predetermined wavelength is in the range of about 500 nm to about 1,000 nm.

36. The method of claim 30 in which the predetermined depth is in the range of about 0.1 mm to about 0.5 mm.

37. The method of claim 30 in which the predetermined area includes a burn area of the human subject.

38. The method of claim 30 in which the predetermined area includes a wound area of a human subject.