Probes and pressure modulation algorithms for reducing extratissue contamination in hemodynamic measurement
The present disclosure provides devices and methods for improved hemodynamic monitoring, including techniques for reducing signals related to hemodynamic activity outside the tissue or region of interest.
1. A method, comprising:
measuring moving particles in a tissue,
the measuring comprising illuminating a first tissue region having moving particles and illuminating a second tissue region superficial to the first tissue region, the second tissue region having moving particles;
with a first source-detector pair, collecting illumination scattered by the moving particles of the first tissue region,
with a second source-detector pair, collecting illumination scattered by the moving particles of the second tissue region,
forming a signal based on the illumination collected by the first source-detector pair and the second source-detector pair,
the source and detector of the first source-detector pair being separated by a first distance,
the source and detector of the second source-detector pair being separated by a second distance, the second distance being greater than the first distance,
the collecting being performed under application of (a) one or more perturbations directed to the second tissue region, (b) one or more perturbations proximate to the location of the first source-detector pair, proximate to the second source source-detector pair, or proximate to both the first and second source-detector pairs, or (c) any combination of (a) and (b),
at least one perturbation effecting a hemodynamic change in the second tissue region,
isolating in the signal an isolated component related to illumination scattered by the moving particles of the second tissue region, and
estimating, based on the isolated component, a hemodynamic quantity of the first tissue region from the collected illumination.
2. The method of claim 1 , wherein the estimating comprises application of the DCS Modified Beer-Lambert law, application of the DOS/NIRS Modified Beer-Lambert Law, or any combination thereof.
3. The method of claim 2 , wherein the estimating comprises application of the DCS Modified Beer-Lambert law, application of the DOS/NIRS Modified Beer-Lambert Law, or any combination thereof, for a multi-layer medium.
4. The method of claim 3 , wherein the estimating comprises application of the DCS Modified Beer-Lambert law, application of the DOS/NIRS Modified Beer-Lambert Law, or any combination thereof, for a two-layer medium.
5. The method of claim 2 , wherein at least one of the parameters of the DCS Modified Beer-Lambert law, application of the DOS/NIRS Modified Beer-Lambert Law, or any combination thereof, is derived from illumination collected from the subject.
6. The method of claim 2 , wherein at least one of the parameters of the DCS Modified Beer-Lambert law, application of the DOS/NIRS Modified Beer-Lambert Law, or any combination thereof, is derived from population measurements.
7. The method of claim 5 , wherein the deriving comprises calculating a value related to illumination gathered at (a) each of two applied pressures, (b) illumination gathered from the first source-detector pair, (c) illumination gathered from the second source-detector pair, or any combination of (a), (b), or (c).
8. The method of claim 1 , wherein the estimating is based on illumination collected at a number of delay time values optimized to be the minimum number of delay time values to provide a sufficient signal-to-noise ratio.
9. The method of claim 1 , wherein the estimating is based on illumination collected at one delay time value.
10. The method of claim 1 , further comprising estimating the first tissue hemodynamic quantity from the collected illumination (a) before, during, and/or after delivery of an agent to the subject, (b) before, during, and/or after the subject engages in an activity, (c) before, during, and/or after physically manipulating the subject, or any combination of the foregoing.
11. The method of claim 1 , wherein estimating the first tissue region hemodynamic quantity from the collected illumination analyzed at the number of delay time values optimized to be the minimum number of delay time values to provide a sufficient signal-to-noise ratio.
12. The method of claim 11 , wherein the estimating is based on illumination collected at one delay time value.
13. The method of claim 1 , further comprising measuring a motion of moving particles in a subject's tissue.
14. The method of claim 13 , wherein the motion comprises a cerebral blood flow.
15. The method of claim 1 , wherein the perturbation is an externally applied perturbation to a subject.
16. A method, comprising:
measuring moving particles in a tissue,
the measuring comprising illuminating a first tissue region having moving particles and illuminating a second tissue region superficial to the first tissue region, the second region having moving particles;
with a first source-detector pair, collecting illumination scattered by the moving particles of the first tissue region,
with a second source-detector pair, collecting illumination scattered by the moving particles of the second tissue region,
forming a signal based on the illumination collected by the first source-detector pair and the second source-detector pair,
the source and detector of the first source-detector pair being separated by a first distance,
the source and detector of the second source-detector pair being separated by a second distance, the second distance being greater than the first distance,
the collecting being performed under application of (a) one or more perturbations directed to the second tissue region, (b) one or more perturbations proximate to the location of the first source-detector pair, proximate to the second source source-detector pair, or proximate to both the first and second source-detector pairs, or (c) any combination of (a) and (b),
at least one perturbation effecting a hemodynamic change in the second tissue region,
isolating in the signal an isolated component related to illumination scattered by the moving particles of the second tissue region, and
estimating a blood flow of the first tissue region from the collected illumination, wherein the estimating comprises application of the DOS/NIRS Modified Beer-Lambert law to the isolated component of the signal.