Determining blood flow using laser speckle imaging
In some examples, a system includes processing circuitry configured to generate a laser speckle contrast signal based on a received signal indicative of detected light, wherein the detected light is scatted by tissue from a coherent light source. The processing circuitry may also determine, from the laser speckle contrast signal, a flow value and determine, from the laser speckle contrast signal, a waveform metric. Based on the flow value and the waveform metric, the processing circuitry may determine a blood flow metric for the tissue and output a representation of the blood flow metric.
1. A system comprising:
light drive circuitry configured to cause a coherent light source to emit light of a single wavelength;
light detection circuitry configured to generate a signal indicative of detected light;
processing circuitry configured to:
control the light drive circuitry to cause the coherent light source to emit the light of the single wavelength;
receive, from the light detection circuitry, the signal indicative of the detected light scattered from the light of the single wavelength;
generate a laser speckle contrast signal based on the signal indicative of the detected light, the detected light scattered by tissue of a subject and from the coherent light source that emitted the light of the single wavelength;
determine, from the laser speckle contrast signal, a flow value;
determine, from the laser speckle contrast signal, a waveform metric;
determine, based on both the flow value and the waveform metric, a blood flow metric for the tissue; and
output, for display at a display device, a representation of the blood flow metric.
2. The system of claim 1 , wherein the processing circuitry is configured to determine the waveform metric by at least determining the waveform metric based on the laser speckle contrast signal comprising at least one of a triphasic waveform, a biphasic waveform, or a monophasic waveform representative of a single cardiac cycle.
3. The system of claim 1 , wherein the processing circuitry is configured to determine the waveform metric by at least:
comparing a waveform shape of the laser speckle contrast signal to a plurality of different waveform templates; and
selecting the waveform metric corresponding to one waveform template of the plurality of different waveform templates that best fits the waveform shape.
4. The system of claim 1 , wherein the processing circuitry is configured to determine the blood flow metric based on a total score of the flow value and the waveform metric.
5. The system of claim 1 , wherein the processing circuitry is configured to determine the blood flow metric from a lookup table defining a relationship between the flow value and the waveform metric.
6. The system of claim 1 , wherein the processing circuitry is configured to:
determine the flow value by at least determining an average flow of a plurality of waveforms of the laser speckle contrast signal; and
determine the waveform metric by at least determining an average slope of the plurality of waveforms of the laser speckle contrast signal.
7. The system of claim 1 , wherein the processing circuitry is configured to determine a peripheral vascular disease metric based on the blood flow metric for the tissue.
8. The system of claim 1 , wherein the tissue comprises a digit of the subject.
9. The system of claim 1 , further comprising the display device configured to present the representation of the blood flow metric.
10. The system of claim 1 , further comprising:
the coherent light source; and
a light detector configured to detect light scattered by the tissue from the coherent light source and generate the signal indicative of the detected light.
11. A method comprising:
controlling, by processing circuitry, light drive circuitry configured to cause a coherent light source to emit light of a single wavelength;
generating, by light detection circuitry, a signal indicative of detected light scattered from the light of the single wavelength;
receiving, by the processing circuitry and from the light detection circuitry, the signal indicative of detected light;
generating, by the processing circuitry, a laser speckle contrast signal based on a the signal indicative of the detected light, the detected light scattered by tissue of a subject and from the coherent light source that emitted the light of the single wavelength;
determining, by the processing circuitry and from the laser speckle contrast signal, a flow value;
determining, by the processing circuitry and from the laser speckle contrast signal, a waveform metric;
determining, by the processing circuitry and based on both the flow value and the waveform metric, a blood flow metric for the tissue; and
outputting, by the processing circuitry and for display at a display device, a representation of the blood flow metric.
12. The method of claim 11 , wherein determining the waveform metric comprises determining the waveform metric based on the laser speckle contrast signal comprising one of a triphasic waveform, a biphasic waveform, or a monophasic waveform representative of a single cardiac cycle.
13. The method of claim 11 , wherein determining the waveform metric comprises:
comparing a waveform shape of the laser speckle contrast signal to a plurality of different waveform templates; and
selecting the waveform metric corresponding to one waveform template of the plurality of different waveform templates that best fits the waveform shape.
14. The method of claim 11 , wherein determining the blood flow metric comprises determining the blood flow metric based on a total score of the flow value and the waveform metric.
15. The method of claim 11 , wherein determining the blood flow metric comprises determining the blood flow metric from a lookup table defining a relationship between the flow value and the waveform metric.
16. The method of claim 11 , wherein:
determining the flow value comprises calculating an average flow of a plurality of waveforms of the laser speckle contrast signal; and
determining the waveform metric comprises calculating an average slope of the plurality of waveforms of the laser speckle contrast signal.
17. The method of claim 11 , further comprising determining a peripheral vascular disease metric based on the blood flow metric for the tissue.
18. The method of claim 11 , wherein the tissue comprises a digit of a subject, and wherein the method further comprises:
delivering, via the coherent light source, the coherent light to the tissue of the digit;
detecting, via a light detector, the light scattered by the tissue of the digit from the coherent light source; and
generating, via the light detector and by the light detection circuitry, the signal indicative of the detected light.
19. The method of claim 11 , further comprising presenting, via the display device, the representation of the blood flow metric.
20. A non-transitory computer-readable medium comprising instructions that, when executed, causes processing circuitry to:
control light drive circuitry to cause a coherent light source to emit light of a single wavelength;
receive, from light detection circuitry, a signal indicative of detected light, wherein the light detection circuitry is configured to generate the signal indicative of the detected light;
generate a laser speckle contrast signal based on the signal indicative of the detected light, the detected light scattered by tissue of a subject and from the coherent light source that emitted the light of the single wavelength;
determine, from the laser speckle contrast signal, a flow value;
determine, from the laser speckle contrast signal, a waveform metric;
determine, based on both the flow value and the waveform metric, a blood flow metric for the tissue; and
output, for display at a display device, a representation of the blood flow metric.