MULTISPECTRAL MEDICAL IMAGING DEVICES AND METHODS THEREOF

• US 20160022181A1
• Filed: 07/25/2014
• Published: 01/28/2016
• Est. Priority Date: 07/25/2014
• Status: Active Grant

• Current Assignee: Christie Digital Systems Canada Incorporated (Ushio Incorporated)
• Original Assignee: Christie Digital Systems USA Incorporated (Ushio Incorporated)
• Inventors: ZAREI MAHMOODABADI, Sina, WAGNER, Robert Benjamin, VALSAN, Gopal, PRIEST, David, AMELARD, Robert
• Granted Patent: US 9,968,285 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: A61B 2576/02 specially adapted for a particular organ or body part
• CPC Class Codes: A61B 5/02007 Evaluating blood vessel condition, e.g. elasticity, compliance
• CPC Class Codes: A61B 5/0261 using optical means, e.g. infrared light
• CPC Class Codes: A61B 5/1455 using optical sensors, e.g. spectral photometrical oximeters
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/489 Blood vessels
• CPC Class Codes: A61B 5/70 Means for positioning the patient in relation to the detecting, measuring or recording means
• CPC Class Codes: A61B 5/7207 of noise induced by motion artifacts
• CPC Class Codes: A61B 5/742 using visual displays A61B5/339 takes precedence
• CPC Class Codes: G16H 30/40 for processing medical images, e.g. editing

Abstract

A multispectral medical imaging device includes illumination devices arranged to illuminate target tissue. The illumination devices emit light of different near-infrared wavelength bands. The device further includes an objective lens, a near-infrared image sensor positioned to capture image frames reflected from the target tissue, and a visible-light image sensor positioned to capture image frames reflected from the target tissue. A processor is configured to modulate near-infrared light output of the plurality of illumination devices to illuminate the target tissue. The processor is further configured to determine reflectance intensities from the image frames captured by the near-infrared image sensor and to generate a dynamic tissue oxygen saturation map of the target tissue using the reflectance intensities. The device further includes an output device connected to the processor for displaying the dynamic tissue oxygen saturation map.

Claims

1. A multispectral medical imaging device comprising:

a plurality of illumination devices arranged to illuminate a target tissue, the plurality of illumination devices configured to emit light of different near-infrared wavelength bands;

an objective lens;

a near-infrared image sensor positioned to capture image frames reflected from the target tissue through the objective lens;

a visible-light image sensor positioned to capture image frames reflected from the target tissue through the objective lens;

a processor connected to the near-infrared image sensor, the visible-light image sensor, and the plurality of illumination devices, the processor configured to modulate near-infrared light output of the plurality of illumination devices to illuminate the target tissue, the processor further configured to determine reflectance intensities from the image frames captured by the near-infrared image sensor and to generate a dynamic tissue oxygen saturation map of the target tissue using the reflectance intensities; and

an output device connected to the processor for displaying the dynamic tissue oxygen saturation map.

2. The device of claim 1, wherein the processor is configured to generate the dynamic tissue oxygen saturation map of the target tissue by comparing the reflectance intensities to a reference standard.

3. The device of claim 1, wherein the plurality of illumination devices are arranged in a ring around the objective lens.

4. The device of claim 1, wherein the plurality of illumination devices comprises at least four illumination devices having near-infrared wavelength bands with nominal peak wavelengths of about 740, 780, 850 and 940 nm.

5. The device of claim 1, further comprising a dichroic beam splitter positioned between the objective lens and the near-infrared and visible-light image sensors, the dichroic beam splitter arranged to split light from the objective lens between the near-infrared and visible-light image sensors.

6. The device of claim 1, further comprising a white-light illumination device arranged to illuminate the target tissue with visible light.

7. The device of claim 1, wherein the output device comprises a display for viewing by a clinician.

8. The device of claim 1, wherein the output device comprises a projector positioned to project the dynamic tissue oxygen saturation map onto a skin surface over the target tissue.

9. The device of claim 1, wherein the processor is configured to modulate the plurality of illumination devices to illuminate the target tissue by sequentially driving the plurality of illumination devices, wherein each image frame in a sequence of the image frames corresponds to illumination of the target tissue by a different wavelength band.

10. The device of claim 9, wherein the processor is configured to perform rolling processing on a window of image frames corresponding to illumination of the target tissue by each of the illumination devices.

11. The device of claim 9, wherein a frame rate of the dynamic tissue oxygen saturation map is approximately equal to a combined frequency of modulation of all of the plurality of illumination devices.

12. The device of claim 1, wherein the processor is further configured to perform motion correction on image frames captured by the near-infrared image sensor, the motion correction comprising selecting a reference frame from the image frames and calculating image registration coefficients for at least one subsequent frame of the image frames.

13. The device of claim 12, wherein calculating image registration coefficients comprises performing a space transformation on the reference frame and the at least one subsequent frame.

14. The device of claim 12, wherein calculating image registration coefficients comprises performing feature detection on the reference frame and the at least one subsequent frame.

15. The device of claim 12, wherein the processor is further configured to calculate image registration coefficients for the motion correction using sub-regions of the image frames captured by the near-infrared image sensor, the sub-regions having dimensions smaller than a size of the image frames and being located away from edges of the image frames.

16. The device of claim 12, wherein the processor is further configured to perform motion correction on image frames captured by the visible-light image sensor.

17. The device of claim 16, wherein the motion correction comprises performing feature detection including detection of an ink mark on a skin surface over the target tissue.

18. The device of claim 16, wherein the motion correction comprises performing feature detection including detection of body hair on skin over the target tissue.

19. The device of claim 18, wherein the motion correction comprises performing feature detection including detection of vasculature of the target tissue.

20. The device of claim 1, wherein the processor is further configured to use output of the visible-light image sensor to determine a correction for melanin in skin over the target tissue and to apply the correction to the reflectance intensities of the image frames captured by the near-infrared image sensor.

21. The device of claim 20, wherein the processor is configured to determine the correction from a predetermined relationship between visible light reflected intensity and melanin concentration.

22. The device of claim 1, wherein the processor is further configured to use the near-infrared image sensor to capture at least one ambient infrared image of the target tissue when controlling all of the illumination devices to not illuminate the target tissue, the processor further configured to subtract the ambient infrared image from the captured image frames.

23. The device of claim 22, wherein the processor is further configured to repeatedly capture ambient infrared images and to subtract a most recent ambient infrared image from subsequently captured image frames.

24. The device of claim 22, wherein the processor is further configured to trigger capture of the ambient infrared image based on a change in ambient infrared illumination that exceeds a threshold.

25. The device of claim 24, further comprising an ambient-light sensor connected to the processor and configured to detect the change in ambient infrared illumination.

26. The device of claim 24, further comprising a visible-light image sensor connected to the processor and configured to detect a change in ambient visible illumination indicative of the change in ambient infrared illumination.

27. The device of claim 1, wherein the processor is further configured to mask a region of the dynamic tissue oxygen saturation map where intensities of the region in image frames of different near-infrared wavelength bands indicate a threshold amount of curvature of the target tissue.

28. The device of claim 1, wherein the processor is further configured to perform a temporal difference operation on a sequence of frames of the dynamic tissue oxygen saturation map with respect to a reference frame of the dynamic tissue oxygen saturation map.

29. The device of claim 1, wherein the processor is further configured to use the image frames to calculate a rate of desaturation of hemoglobin in the target tissue over a period of time for determining a venous or arterial blockage.

30. The device of claim 1, wherein the processor is further configured to use the image frames to identify veins in the target tissue and to modify reflectance intensities to compensate for oxygenation or deoxygenating at the veins when generating the dynamic tissue oxygen saturation map.

31. The device of claim 1, further comprising at least one laser positioned to emit a plurality of laser points onto a skin surface over the target tissue, the laser points for assisting manual positioning of the device with respect to the target tissue.

32. The device of claim 31, further comprising a visible-light image sensor connected to the processor for capturing light from the laser points reflected from the skin surface, the processor further configured to include the laser points in the dynamic tissue oxygen saturation map.

33. The device of claim 31, wherein the at least one laser is configured to emit the plurality of laser points at a near-infrared wavelength band detectable by the near-infrared image sensor to include the laser points in the dynamic tissue oxygen saturation map.

34. The device of claim 31, further comprising optics configured to emit lines of laser light onto the skin surface over the target tissue, the lines of laser light including the laser points.

35. The device of claim 34, wherein the lines of laser light are arranged as a rectangular box.

36. The device of claim 1, further comprising:

a first positioning laser positioned at a first offset distance from an optical axis of the objective lens and aimed at a first angle with respect to the optical axis to emit a first positioning laser spot on a skin surface over the target tissue; and

a second positioning laser positioned at a second offset distance from the optical axis of the objective lens and aimed at a second angle with respect to the optical axis to emit a second positioning laser spot on the skin surface;

the first and second angles laying in different planes that contain the optical axis, and the first and second offset distances and angles are selected to cause the first positioning laser spot and the second positioning laser spot to be coincident at the optical axis when the target tissue is a target distance from the objective lens.

37. The device of claim 36, wherein the first and second offset distances and angles are configured to position the first and second positioning laser spots on one side of the optical axis of the objective lens when a distance from the objective lens to the target tissue is greater than the target distance and to position the first and second positioning laser spots on an opposite side of the target when the distance from the objective lens to the target tissue is less than the target distance.

38. The device of claim 36, wherein the first and second positioning lasers are positioned at about 90 degrees apart on a circle centered at the optical axis of the objective lens.

39. The device of claim 1, wherein the processor is further configured to align captured visible-light image frames with captured near-infrared image frames using displacement coefficients stored in memory, the displacement coefficients being predetermined based on image registration performed on at least one standard image captured by both of the near-infrared image sensor and the visible-light image sensor.

40. A method for multispectral medical imaging, the method comprising:

illuminating a target tissue with modulated light of different near-infrared wavelength bands;

capturing near-infrared image frames reflected from the target tissue;

capturing visible-light image frames reflected from the target tissue;

determining reflectance intensities from the near-infrared image frames;

correcting the reflectance intensities of the near-infrared image frames using information from the visible-light image frames;

generate a dynamic tissue oxygen saturation map of the target tissue using the reflectance intensities; and

outputting the dynamic tissue oxygen saturation map.