Patent ID: 8082016

Claim:
A method of determining concentration of a fluorescent indicator that is indocyanine green (ICG) having a concentration C ICG within the cardiovascular system of a subject comprising: a. administering to the cardiovascular system a detectable amount of the indicator that fluoresces when illuminated; b. illuminating a portion of the cardiovascular system with an excitation light of a first wavelength and causing the administered indicator to emit an emergent fluorescence light of a second wave length; c. detecting the intensity (x) of the excitation light that is reflected by or transmitted through a portion of the cardiovascular system; d. detecting the intensity (y) of the emergent fluorescence light; e. determining the ratio (y)/(x); f. determining the concentration (C ICG ) of the fluorescence indicator in the cardiovascular system based on the determined ratio (y)/(x), wherein the concentration of the fluorescence indicator is proportional to the ratio; and g. determining a ratio C ICG /C Hb of indocyanine green concentration (C ICG ) to the blood hemoglobin concentration (C Hb ) wherein the ratio C ICG /C Hb is proportional to the change of the ratio (y)/(x).