Method and apparatus for the in vivo measurement of oxygen concentration levels by the indirect determination of fluoescence lifetime
First Claim
1. A method of measuring oxygen concentration or partial pressure in bodily fluid or tissue of a living being, the method comprising the steps of:
- (a) administering a biocompatible, lipid soluble fluorescent probe substance having a fluorescence lifetime (τ
) which is quenched by molecular oxygen, to the living being;
(b) irradiating the tissue or bodily fluid with continuous, linearly polarized ultraviolet light at wavelengths strongly absorbed by the fluorescent probe substance to result in fluorescence having vector components parallel and perpendicular to the plane of polarization of the ultraviolet light;
(c) resolving the fluorescence emitted from the irradiated tissue or bodily fluid of step (b) into vector components parallel and perpendicular to the plane of polarization of the excitation light;
(d) calculating fluorescence anisotropy in space or in time of the tissue or fluid so irradiated; and
(e) applying a mathematical function which relates fluorescence anisotropy to oxygen concentration or partial pressure, the mathematical function being in the form of an equation.
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Abstract
Methods are described for the in vivo topographic determination of tissue and bodily fluid oxygen concentration or PO2 within an imaged tissue, as well as a method for measuring blood or bodily fluid PO2 with a fiber optic catheter. In the first method, a lipid soluble, biocompatible fluorescent probe substance is administered to an animal body and accumulates within the lipid bilayers of its tissue cells. In the second method, the fluorescent probe substance is conjugated to a large molecular mass protein which causes it to be retained within a bodily fluid such as blood. In the third method describing a catheter design, in which PO2 is measured at the catheter tip, the tip contains the fluorescent probe substance dissolved in a viscous nonpolar solvent. In all methods described, a fluorescent probe substance is preferred whose fluorescence lifetime is quenched by molecular oxygen, and oxygen concentration or PO2 is determined by measuring the fluorescence anisotropy of the fluorescent probe substance. The bodily fluid or tissue containing the biocompatible fluorescent probe substance, or the fluorescent probe substance in a nonpolar solvent within a catheter tip, is irradiated with continuous linearly polarized ultraviolet light at a wavelength strongly absorbed by the fluorophore. The emitted fluorescence is resolved into its vector components parallel and perpendicular to the plane of polarization of the excitation light, thereby permitting the calculation of the fluorescence anisotropy of the irradiated specimen. Tissue and/or bodily fluid PO2 of the imaged specimen, or the PO2 of a fluid at the tip of a sealed catheter, is determined by applying a mathematical function which relates the fluorescence anisotropy of an O2 -quenchable fluorophore to oxygen concentration or partial pressure.
72 Citations
20 Claims
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1. A method of measuring oxygen concentration or partial pressure in bodily fluid or tissue of a living being, the method comprising the steps of:
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(a) administering a biocompatible, lipid soluble fluorescent probe substance having a fluorescence lifetime (τ
) which is quenched by molecular oxygen, to the living being;(b) irradiating the tissue or bodily fluid with continuous, linearly polarized ultraviolet light at wavelengths strongly absorbed by the fluorescent probe substance to result in fluorescence having vector components parallel and perpendicular to the plane of polarization of the ultraviolet light; (c) resolving the fluorescence emitted from the irradiated tissue or bodily fluid of step (b) into vector components parallel and perpendicular to the plane of polarization of the excitation light; (d) calculating fluorescence anisotropy in space or in time of the tissue or fluid so irradiated; and (e) applying a mathematical function which relates fluorescence anisotropy to oxygen concentration or partial pressure, the mathematical function being in the form of an equation. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification