Methods for depth estimation in laser speckle imaging

Patent metadata

Field	Value
Publication number	US-10871503-B1
Application number	US-201815953222-A
Country	US
Kind code	B1
Filing date	Apr 13, 2018
Priority date	May 26, 2015
Publication date	Dec 22, 2020
Grant date	Dec 22, 2020

Abstract

Systems and methods are provided for detecting the depth, flow rate, and other properties of regions of blood flow in biological tissue by illuminating the biological tissue with beams of coherent light and detecting responsively emitted light. This includes detecting lights emitted from the tissue having a plurality of respective different exposure times. The relationship between the intensity of the received light and the exposure times is determined and used to determine the depth, flow velocity, or other properties of regions of flow within the biological tissue. This can include determining a spatial and/or temporal contrast of the received light intensity. Determining the depth of a region of flow can include comparing determined properties of light received from the tissue at two different polarizations. Determining the depth of a region of flow can include comparing determined properties of light received from the tissue at two different locations.

First claim

What is claimed is:

1. A device comprising:
a light source;
at least one light sensor; and
a controller, wherein the controller comprises a computing device programmed to perform operations comprising:
during each of a plurality of time periods, wherein each time period is associated with a respective exposure time of a set of exposure times:
emitting, by the light source, a beam of polarized coherent illumination into a biological tissue;
detecting, using the at least one light sensor, an intensity of light of a first polarization received from a portion of the biological tissue during an exposure time;
detecting, using the at least one light sensor, an intensity of light of a second polarization received from the portion of the biological tissue during the exposure time;
determining, for each exposure time in the set of exposure times, a first contrast value and a second contrast value, wherein determining a first contrast value for a given exposure time comprises determining an amount of variation between at least two intensities of light of the first polarization detected during at least two time periods associated with the given exposure time, and wherein determining a second contrast value for the given exposure time comprises determining an amount of variation between at least two intensities of light of the second polarization detected during at least two time periods associated with the given exposure time; and
determining a depth of a region of flow within the biological tissue as a function of the determined first contrast values and the determined second contrast values.

2. The device of claim 1 , further comprising:
an endoscopic probe configured to be inserted into a body cavity, wherein the light source is configured to emit light from the endoscopic probe, and wherein the at least one light sensor is configured to detect light received from the biological tissue via the endoscopic probe.

3. The device of claim 1 , wherein the operations further comprise:
determining a flow velocity within the region of flow as a function of the determined first contrast values.

4. The device of claim 3 , wherein the determined flow velocity is a flow velocity of blood cells in the region of flow.

5. The device of claim 3 , wherein determining a flow velocity within the region of flow as a function of the determined first contrast values comprises:
detecting a feature in the determined first contrast values;
determining an exposure time corresponding to the detected feature; and
using the determined exposure time to determine a flow velocity within the region of flow.

6. The device of claim 1 , wherein the operations further comprise: during each of the plurality of time periods:
detecting, using the at least one light sensor, an intensity of light of the first polarization received from a further portion of the biological tissue during an exposure time; and
detecting, using the at least one light sensor, an intensity of light of the second polarization received from the further portion of the biological tissue during an exposure time;
determining, for each exposure time in the set of exposure times, a third contrast value and a fourth contrast value, wherein determining a third contrast value for a given exposure time comprises determining an amount of variation between at least two intensities of light of the first polarization received from the further portion of biological tissue detected during at least two time periods associated with the given exposure time, and wherein determining a fourth contrast value for the given exposure time comprises determining an amount of variation between at least two intensities of light of the second polarization received from the further portion of biological tissue detected during at least two time periods associated with the given exposure time;
determining a depth of a further region of flow within the biological tissue as a function of the determined third contrast values and the determined fourth contrast values; and
using the determined depths of regions of flow within the biological tissue to generate a map of one or more portions of vasculature in the biological tissue.

7. The device of claim 1 , wherein determining a depth of a region of flow within the biological tissue as a function of the determined first contrast values and the determined second contrast values comprises:
detecting a feature in the determined first contrast values;
determining an exposure time corresponding to the detected feature;
determining a ratio between a determined first contrast value corresponding to the determined exposure time and a determined second contrast value corresponding to the determined exposure time; and
using the determined ratio to determine the depth of the region of flow.

8. The device of claim 1 , wherein determining a depth of a region of flow within the biological tissue as a function of the determined first contrast values and the determined second contrast values comprises:
detecting a feature in the determined first contrast values;
determining an exposure time corresponding to the detected feature;
determining a difference between a determined first contrast value corresponding to the determined exposure time and a determined second contrast value corresponding to the determined exposure time; and
using the determined difference to determine the depth of the region of flow.

9. The device of claim 1 , wherein each time period being associated with a respective exposure time comprises the controller operating the at least one light sensor, during each time period, to detect light during an integration time having a duration corresponding to the exposure time of the time period.

10. The device of claim 1 , wherein each time period being associated with a respective exposure time comprises the controller operating the light source, during each time period, to emit a pulse of light having a duration corresponding to the exposure time of the time period.

11. A device comprising:
a light source;
at least one light sensor; and
a controller, wherein the controller comprises a computing device programmed to perform operations comprising:
during each of a plurality of time periods, wherein each time period is associated with a respective exposure time of a set of exposure times:
emitting, by the light source, a beam of coherent illumination into a biological tissue;
detecting, using the at least one light sensor, an intensity of light received from a first portion of the biological tissue during an exposure time;
detecting, using the at least one light sensor, an intensity of light received from a second portion of the biological tissue during the exposure time;
determining, for each exposure time in the set of exposure times, a first contrast value and a second contrast value, wherein determining a first contrast value for a given exposure time comprises determining an amount of variation between at least two intensities of light received from the first portion of biological tissue detected during at least two time periods associated with the given exposure time, and wherein determining a second contrast value for the given exposure time comprises determining an amount of variation between at least two intensities of light received from the second portion of biological tissue detected during at least two time periods associated with the given exposure time; and
determining a depth of a region of flow within the biological tissue as a function of the determined first contrast values and the determined second contrast values.

12. The device of claim 11 , further comprising:
an endoscopic pr

Assignees

• Verily Life Sciences Llc

Inventors

• Homyk Andrew
• Thompson Jason Donald

Classifications

• A61B5/02042

  Determining blood loss or bleeding, e.g. during a surgical procedure · CPC title

• G01S17/50

  Systems of measurement based on relative movement of target · CPC title

• A61B5/489

  Blood vessels · CPC title

• G01S7/4815

  using multiple transmitters · CPC title

• G01S17/88

  Lidar systems specially adapted for specific applications · CPC title