Optical imaging methods

• US 5,845,639 A
• Filed: 11/11/1994
• Issued: 12/08/1998
• Est. Priority Date: 08/10/1990
• Status: Expired due to Term

• Current Assignee: Board of Regents of The University of Washington (University of Washington)
• Original Assignee: Board of Regents of The University of Washington (University of Washington)
• Inventors: Hochman, Daryl, Haglund, Michael M.
• Primary Examiner(s): Casler, Brian L.
• Application Number:
  US08/339,149
• Time in Patent Office: 1,488 Days
• Field of Search: 128/653.1, 128/664, 128/665, 128/691, 128/661.09, 128/633, 364/413.13, 356/39-41
• US Class Current: 600/407
• CPC Class Codes: A61B 5/0059 using light, e.g. diagnosis by transillumination, diascopy, fluorescence A61B5/0093, A61B5/1455, A61B5/02416 and A61B5/0261 take precedence
• CPC Class Codes: A61B 5/14553 specially adapted for cerebral tissue
• CPC Class Codes: A61B 5/4094 Diagnosing or monitoring seizure diseases, e.g. epilepsy
• CPC Class Codes: A61B 90/36 Image-producing devices or illumination devices not otherwise provided for
• CPC Class Codes: G06T 5/50 using two or more images, e.g. averaging or subtraction
• CPC Class Codes: G16H 15/00 ICT specially adapted for medical reports, e.g. generation or transmission thereof
• CPC Class Codes: G16H 20/40 relating to mechanical, radiation or invasive therapies, e.g. surgery, laser therapy, dialysis or acupuncture
• CPC Class Codes: G16H 30/20 for handling medical images, e.g. DICOM, HL7 or PACS
• CPC Class Codes: Y02A 90/10 Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation
• CPC Class Codes: Y10S 128/922 including image analysis

Abstract

Methods for optically imaging blood flow changes, blood flow characteristics and changes in the oxygenation of blood in an area of interest are disclosed. The area of interest is illuminated with electromagnetic radiation(emr) in the visible or infrared regions of the spectrum, and a control image representative of the emr absorption of the area of interest is acquired. A subsequent image representative of the emr absorption is compared to the control image to detect changes in the emr absorption that are indicative of changes in blood flow, changes in blood flow characteristics, or changes in blood oxygenation in the area of interest.

Claims

1. A method for optically imaging blood flow changes in an area of interest, comprising:

illuminating the area of interest with uniform intensity electromagnetic radiation (emr), the emr being in one of the visible and infrared regions of the spectrum;

acquiring a series of control frames representative of the emr absorption of the area of interest in the absence of a fluorescent dye and processing the control frames to produce an averaged control image;

acquiring a series of subsequent frames representative of the emr absorption of the area of interest in the absence of a fluorescent dye and processing the subsequent frames to produce an averaged subsequent image; and

obtaining a difference image by one of subtracting pixel values in the averaged control image from corresponding pixel values in the subsequent averaged image, and subtracting pixel values in the subsequent averaged image from corresponding pixel values in the averaged control image to identify changes in the emr absorption of the area of interest occurring between acquisition of the control frames and acquisition of the subsequent frames, wherein the changes in the emr absorption represent changes in blood flow.

2. A method according to claim 1, additionally comprising assigning each pixel having a negative value in the difference image a value of zero.

3. A method according to claim 1, wherein the difference image is obtained by subtracting the averaged control image from the subsequent averaged image, and additionally comprising obtaining a second difference image by subtracting the subsequent averaged image from the averaged control image and adding the difference image and the second difference image to obtain a sum difference image.

4. A method according to claim 1, wherein the difference image is obtained by subtracting the subsequent average control image from the averaged control image, and additionally comprising obtaining a second difference image by subtracting the averaged control image from the subsequent averaged image and adding the difference image and the second difference image to obtain a sum difference image.

5. A method according to claim 1, wherein the emr has a wavelength greater than about 690 nm.

6. A method according to claim 1, additionally comprising mapping positive pixel values in the difference image to a first color;

mapping negative pixel values in the difference image to a second color; and

mapping pixels having a value of zero to a third color to enhance visibility of blood flow changes indicated by the difference image.

7. A method according to claim 1, additionally comprising compensating for movement of the area of interest by aligning corresponding spatial areas of the averaged control image and the averaged subsequent image.

8. A method according to claim 7, wherein the compensating is achieved by means of computations.

9. A method according to claim 1, additionally comprising administering a dye that migrates to the area of interest prior to acquiring the series of control frames.

10. A method for optically imaging blood flow characteristics of an area of interest comprising tissue having one or more blood vessels, the method comprising:

illuminating the area of interest with uniform intensity electromagnetic radiation (emr), the emr being in one of the visible and infrared regions of the spectrum;

acquiring a control image representative of the emr absorption of the area of interest in the absence of a fluorescent dye at one of a control time point and a control time interval;

acquiring a subsequent image representative of the emr absorption of the area of interest in the absence of a fluorescent dye at one of a control time point and a subsequent time interval; and

comparing the control image with the subsequent image by one of subtracting the control image from the subsequent image and subtracting the subsequent image from the control image to produce a comparison image that identifies changes in emr absorption that are indicative of changes in blood flow characteristics within one or more blood vessels in the area of interest.

11. A method according to claim 10, wherein the emr has a wavelength greater than about 690 nm.

12. A method according to claim 10, wherein the control image and the subsequent image are obtained as analog video signals and the analog video signals are amplified and spread across a full dynamic range.

13. A method for detecting changes in the oxygenation of blood in an area of interest, comprising:

illuminating the area of interest with uniform intensity electromagnetic radiation (emr), the emr being in one of the visible and infrared regions of the spectrum;

detecting an initial emr absorption level of the area of interest in the absence of a fluorescent dye at one of a control time point and a control time interval, the initial emr absorption level indicating a baseline level of blood oxygenation;

detecting a subsequent emr absorption level of the area of interest in the absence of a fluorescent dye at one of a subsequent time point and a subsequent time interval, the subsequent emr absorption level indicating a subsequent level of blood oxygenation; and

comparing the initial emr absorption level with the subsequent emr absorption level to detect changes in blood oxygenation over time in the area of interest.

14. A method according to claim 13, wherein the emr has a wavelength greater than about 690 nm.