Method for evaluating blush in myocardial tissue
Vessel perfusion and myocardial blush are determined by analyzing fluorescence signals obtained in a static region-of-interest (ROI) in a collection of fluorescence images of myocardial tissue. The blush value is determined from the total intensity of the intensity values of image elements located within the smallest contiguous range of image intensity values containing a predefined fraction of a total measured image intensity of all image elements within the ROI. Vessel (arterial) peak intensity is determined from image elements located within the ROI that have the smallest contiguous range of highest measured image intensity values and contain a predefined fraction of a total measured image intensity of all image elements within the ROI. Cardiac function can be established by comparing the time differential between the time of peak intensity in a blood vessel and that in a region of neighboring myocardial tissue both pre and post procedure.
1. A method for assessing improvement in tissue perfusion resulting from a surgical procedure, the method comprising:
acquiring time series of fluorescence images of the tissue before and after the surgical procedure;
defining a region of interest (ROI) in the time series of fluorescence images of the tissue;
determining at least one of a blush rate and a washout rate for the ROI from the fluorescence images acquired before the surgical procedure and at least one of a blush rate and a washout rate for the ROI from the fluorescence images acquired after the surgical procedure; and assessing improvement in perfusion of the tissue resulting from the surgical procedure by comparing the determined at least one of a blush rate and a washout rate from before the surgical procedure with the determined at least one of a blush rate and a washout rate from after the surgical procedure;
wherein the at least one of a blush rate and a washout rate determined before and after the procedure are determined from a slope of blush values; and
wherein the blush values are determined from an average of intensity values of image elements located within a smallest contiguous range of image intensity values containing a first predefined fraction of total measured image intensity of image intensities within the ROI.
2. The method of claim 1 , wherein the slope of blush values is a slope of a straight line connecting a low threshold point and a high threshold point in an average intensity curve.
3. The method of claim 1 , wherein the blush values are determined over a predefined period of time.
4. The method of claim 1 , wherein the smallest contiguous range of image intensity values is determined from a histogram of a frequency occurrence of the total measured image intensity.
5. The method of claim 1 , wherein the first predefined fraction is between 70% and 30%.
6. The method of claim 2 , wherein the at least one of a blush rate and a washout rate determined before and after the procedure are determined from a least-squares curve fit.
7. The method of claim 1 , further comprising:
defining a second ROI in the time series of fluorescence images of the tissue, with the second ROI including an arterial blood vessel, and
determining a measure of peak intensity of the arterial blood vessel from a total intensity of intensity values of image elements located within a smallest contiguous range of high image intensity values containing a second predefined fraction of a total measured image intensity of brightest image elements within the second ROI.
8. The method of claim 7 , wherein the second predefined fraction is approximately 20%.
9. The method of claim 1 , wherein the ROI is a static ROI.
10. A system for indicating improvement in tissue perfusion resulting from a surgical procedure, the system comprising:
an illumination source for exciting fluorescence in the tissue;
an imager for acquiring a time series of fluorescence images of the tissue before and after the surgical procedure; and
a display and processor; the display and processor configured for:
displaying the fluorescence images and defining a region of interest (ROI) in the fluorescence images,
determining at least one of a blush rate and a washout rate for the ROI from the time series of fluorescence images of the tissue before and after the procedure; and
displaying the at least one of a blush rate and a washout rate determined from the fluorescence images captured before the surgical procedure and the at least one of a blush rate and a washout rate determined from the fluorescence images captured after the surgical procedure, wherein a difference between the at least one of a blush rate and a washout rate before and after the surgical procedure is indicative of whether perfusion of the tissue has improved as a result of the surgical procedure;
wherein the at least one of a blush rate and a washout rate determined before and after the procedure are determined from a slope of blush values; and
wherein the blush values are determined from an average of intensity values of image elements located within a smallest contiguous range of image intensity values containing a first predefined fraction of total measured image intensity of image intensities within the ROI.
11. The system of claim 10 , wherein the slope of blush values is a slope of a straight line connecting a low threshold point and a high threshold point in an average intensity curve.
12. The system of claim 10 , wherein the blush values are determined over a predefined period of time.
13. The system of claim 10 , wherein the smallest contiguous range of image intensity values is determined from a histogram of a frequency occurrence of the total measured image intensity.
14. The system of claim 10 , wherein the first predefined fraction is between 70% and 30%.
15. The system of claim 10 , wherein the at least one of a blush rate and a washout rate determined before and after the procedure are determined from a least-squares curve fit.
16. The system of claim 10 , wherein the illumination source has a peak emission wavelength that is within a range of 780 to 800 nm.
17. The system of claim 10 , wherein the imager is configured to acquire a color image of the tissue.