System for analyzing tissue perfusion using concentration of indocyanine green in blood
View Patent ↗The present invention relates, in general, to a system for analyzing tissue perfusion using the concentration of indocyanine green and a method of measuring the perfusion rate using the system and, more particularly, to a system for measuring tissue perfusion by injecting indocyanine green into a living body, detecting variation in the concentration of indocyanine green with the passage of time, and analyzing the detected variation, and a method of measuring the perfusion rate using the system. The present invention provides a method of measuring perfusion in a living body, which enables accurate measurement for respective regions in a wide range from a perfusion rate decreased to less than 10% of normal perfusion to a perfusion rate increased to greater than normal perfusion using the above-described mechanism of ICG in a living body, which cannot be conducted using the conventional technology.
1. A computer for measuring a rate of tissue perfusion using time-series analysis of fluorescence images of indocyanine green (ICG), comprising:
1) an input module configured to receive signals from a photodetector,
2) a numerical conversion module configured to process input signals from the input module into numerical values, said input signals comprising intensities of fluorescence over time in a region of interest,
3) a rate calculation module configured to calculate rates of tissue perfusion with using the numerical values and an equation representing dynamics of the ICG, and
4) an output module configured to output results of the calculation,
wherein the equation representing dynamics of the ICG is either
FI
isc
=
PA
P
-
1
/
τ
(
ⅇ
-
t
τ
-
ⅇ
-
Pt
)
or
-
In
τ
-
T
max
τ
=
InP
-
PT
max
,
wherein the FI isc (Fluorescence Intensity ischemia) is an intensity of ICG fluorescence of a measurement target tissue, the P is a rate of tissue perfusion, the A is an intensity of fluorescence obtained from ICG image during the first 1 minute, the τ is t 1/2 /ln2, the t 1/2 is a time at which the intensity of ICG fluorescence is half of a highest value and the T max is a time at which the intensity of ICG fluorescence in an ischemic tissue is highest.
2. An apparatus for measuring tissue perfusion, comprising: a stand configured to allow light to pass therethrough, a light source adjustable to be located to radiate light onto an ICG-injected tissue disposed on the stand, a filter adjustable to be located to filter only near infrared ray wavelengths of 800 to 850 nm from fluorescence signals emitted from the living body under the action of the light source, a detector configured to detect fluorescence light passed through the filter, and the computer of claim 1 operably connected to the detector and configured to image light detected by the detector and measure the rates of tissue perfusion through the analysis of the ICG dynamics with the passage of time.
3. A method of measuring a rate of tissue perfusion, comprising:
1) detecting sequentially a concentration of ICG until the concentration of ICG is decreased to a lowest level by injecting the ICG into a living body, radiating light onto the living body using a light source, and measuring intensities of ICG fluorescence generated in the living body with the passage of time after the injection using a photodetector;
2) processing the sequential concentration of ICG in the living body detected in the step 1) into numerical data by converting the intensities of ICG fluorescence into numerical values for respective regions and respective times; and
3) calculating the rates of perfusion from the numerical values,
wherein the perfusion rates are calculated using the following equation:
FI
isc
=
PA
P
-
1
/
τ
(
ⅇ
-
t
τ
-
ⅇ
-
Pt
)
or
-
In
τ
-
T
max
τ
=
InP
-
PT
max
,
wherein the FI isc (Fluorescence Intensity ischemia) is an intensity of ICG fluorescence of a measurement target tissue, the P is a rate of tissue perfusion, the A is an intensity of fluorescence obtained from ICG image during the first 1 minute, the τ is t 1/2 /ln2, the t 1/2 is a time at which the intensity of ICG fluorescence is half of a highest value and the T max is a time at which the intensity of ICG fluorescence in an ischemic tissue is highest.
4. The method as set forth in claim 3 , further comprising outputting the calculated perfusion rates as a perfusion map.
5. The method as set forth in claim 4 , wherein the perfusion map is constructed by coloring particular pixels with respective colors corresponding to the rates of perfusion according to a color gradient map.
6. A method of measuring a rate of tissue perfusion, comprising:
1) detecting sequentially a concentration of ICG until the concentration of ICG is decreased to a lowest level by injecting the ICG into a living body, radiating light onto the living body using a light source, and measuring intensities of fluorescence generated in the living body with the passage of time using a photodetector and obtaining an ICG blood vessel image diagram using the intensities of fluorescence;
2) acquiring T max by analyzing dynamics of the intensities of ICG fluorescence per respective pixel in the ICG blood vessel image diagram; and
3) calculating the rates of perfusion rate based on the T max ,
wherein the perfusion rates are calculated using the following equation:
-
In
τ
-
T
max
τ
=
In
P
-
PT
max
,
wherein the P is a perfusion rate, and the τ is t 1/2 /ln2, the t 1/2 is a time at which the intensity of ICG fluorescence is half of a highest value and the T max is a time at which the intensity of ICG fluorescence in an ischemic tissue is highest.
7. The method as set forth in claim 6 , further comprising outputting the calculated perfusion rates as a perfusion map.
8. The method as set forth in claim 7 , wherein the perfusion map is constructed by coloring particular pixels with respective colors corresponding to the rates of perfusion according to a color gradient map.
9. A method of predicting a rate of tissue necrosis, comprising outputting a tissue necrosis probability map by indicating the probability of necrosis of a tissue based on the rates of tissue perfusion acquired using the method set forth in claim 3 .
10. The method as set forth in claim 4 , wherein the perfusion map is constructed using a method of acquiring perfusion rates of region of interest (ROI) according to (a) average data of pixels of particular regions, (b) respective pixels, or (c) respective ROIs representing perfusion rates; and representing the perfusion rates using the perfusion map by illustrating the perfusion rates for the ROI with corresponding colors designated according to the perfusion rates.
11. A method of predicting a rate of tissue necrosis, comprising outputting a tissue necrosis probability map by indicating the probability of necrosis of a tissue based on the rates of tissue perfusion acquired using the method set forth in claim 6 .
12. The method as set forth in claim 7 , wherein the perfusion map is constructed using a method of acquiring perfusion rates of region of interest (ROI) according to (a) average data of pixels of particular regions, (b) respective pixels, or (c) respective ROIs representing perfusion rates; and representing the perfusion rates using the perfusion map by illustrating the perfusion rates for the ROI with corresponding colors designated according to the perfusion rates.