Perfusion assessment using transmission laser speckle imaging
Methods and apparatus for measuring perfusion using transmission laser speckle imaging are provided. The apparatus comprises a coherent light source and a detector configured to measure transmitted light associated with an unfocused image at one or more locations. The coherent light source and detector are positioned in a transmission geometry. The apparatus further comprises means for securing the coherent light source and the detector to the tissue sample in a fixed transmission geometry relative to the tissue sample. The apparatus may further comprise at least one processor to receive information from the detector and process detected variations in transmitted light intensity to determine a single metric of perfusion. The method may comprise the steps transilluminating a tissue sample with coherent light, recording spatial and/or temporal variations in the transmitted light signal, determining speckle contrast value(s), and computing a metric of perfusion.
1. An apparatus for determining a metric of tissue perfusion, comprising:
a coherent light source configured to illuminate a tissue sample;
a detector, without a lens, system of lenses, mirror or any other optical instruments for creating a focused image, wherein the detector is configured to receive a plurality of light intensity values associated with an unfocused image of the tissue sample; and
an enclosure configured to accommodate the tissue sample, wherein the enclosure is coupled to the coherent light source and the detector,
wherein the coherent light source and the detector are configured in a transmission geometry with respect to the tissue sample, and
wherein the detector is configured to transfer the plurality of light intensity values to a processor configured to compute a speckle contrast parameter and to determine the metric of tissue perfusion.
2. The apparatus of claim 1 , wherein the enclosure comprises a clam shell configuration.
3. The apparatus of claim 1 , wherein the tissue sample is a finger.
4. The apparatus of claim 1 , wherein the tissue sample is a toe, nostril, or earlobe.
5. The apparatus of claim 1 , wherein the apparatus further comprises an opaque sheet positioned between the detector and the tissue sample, wherein the opaque sheet is configured to adjust an aperture of the detector.
6. The apparatus of claim 1 , wherein the detector is a photodiode.
7. An apparatus for determining a metric of tissue perfusion, comprising:
a coherent light source configured to illuminate a tissue sample;
a detector, without a lens, system of lenses, mirror or any other optical instruments for creating a focused image, wherein the detector is configured to receive a plurality of light intensity values associated with an unfocused image of the tissue sample; and
means for securing the coherent light source and the detector to the tissue sample in a fixed transmission geometry relative to the tissue sample, such that movement of the tissue sample while measuring tissue perfusion does not alter the transmission geometry,
wherein the detector is configured to transfer the plurality of light intensity values to a processor configured to compute a speckle contrast parameter and to determine the metric of tissue perfusion.
8. The apparatus of claim 7 , wherein a field of view of the tissue sample is configured to remain constant upon movement of the tissue sample.
9. The apparatus of claim 7 , wherein the means for securing comprises an enclosure configured to securely accommodate the tissue sample, and wherein the enclosure is coupled to the coherent light source and the detector.
10. The apparatus of claim 9 , wherein the enclosure comprises a clam shell configuration.
11. The apparatus of claim 7 , wherein the tissue sample is a finger.
12. The apparatus of claim 7 , wherein the tissue sample is a toe, nostril, or earlobe.
13. The apparatus of claim 7 , wherein the apparatus further comprises:
an opaque sheet positioned between the detector and the tissue sample, wherein the opaque sheet is configured to adjust an aperture of the detector.
14. A method of determining a metric of perfusion in a tissue sample, comprising:
providing an apparatus comprising an enclosure configured to accommodate the tissue sample, a coherent light source configured to illuminate the tissue sample, and a detector, without a lens, system of lenses, mirror or any other optical instruments for creating a focused image, wherein the detector is configured to receive a plurality of light intensity values associated with an unfocused image of the tissue sample, and wherein the detector is configured to transfer data to a processor;
placing the tissue sample into the enclosure between the coherent light source and the detector;
transilluminating the tissue sample with the coherent light source rendering an unfocused image comprising a plurality of light intensity values, which are captured by the detector;
transferring the light intensity values from the detector to the processor;
computing, by the processor, a speckle contrast parameter based at least in part on the plurality of light intensity values; and
determining, by the processor, the metric of perfusion from the speckle contrast parameter.
15. The method of claim 14 , further comprising:
displaying, by the processor, the determined metric of perfusion.
16. The method of claim 14 , wherein the plurality of light intensity values received by the detector is configured to remain constant upon movement of the tissue sample.
17. The method of claim 14 , wherein the tissue sample is a finger.
18. The method of claim 14 , wherein the tissue sample is a toe, nostril, or earlobe.
19. The method of claim 14 , wherein the computing step comprises computing a speckle contrast parameter based at least in part on all the light intensity values of the plurality of light intensity values of the unfocused image.
20. The apparatus of claim 7 , wherein the means is a clam shell enclosure, a strap, a buckle, an elastic band, tape, adhesives, wraps, ribbons or ties.
21. The apparatus of claim 7 , wherein the means is a strap or elastic band.