Granted Patent B2

US 10,285,603 · App. 14/305,950 · Granted May 14, 2019

Abstract

Claims (28)

1. A method for measuring a time-varying change in an amount of blood in a tissue volume of tissue of a subject, comprising:

administering a fluorescence agent into vasculature supplying the tissue volume of tissue of the subject;

exciting a fluorescence agent in the blood, the fluorescence agent having an instantaneous molar concentration in the blood;

capturing a sequence of fluorescence images of the tissue;

acquiring, from the sequence of fluorescence images of the tissue, a time-varying fluorescence intensity signal emitted by the fluorescence agent during a pulsatile flow of the blood through the tissue volume, wherein:

the pulsatile flow has a diastolic and a systolic phase resembling a conventional photoplethysmogram,

the acquired fluorescence intensity signal comprises a first fluorescence intensity emitted by the fluorescence agent in the blood in the tissue volume during a diastolic phase minimum,

the acquired fluorescence intensity signal comprises a second fluorescence intensity emitted by the fluorescence agent in the blood in the tissue volume during a systolic phase maximum, and

the first and second fluorescence intensities are respectively associated with measures of blood volume during the diastolic phase and the systolic phase; and

computing a change in an aggregate blood layer thickness in the tissue volume based on the first and second fluorescence intensities, wherein the change represents a quantitative measure of tissue blood perfusion in the tissue volume; and

displaying the quantitative measure to facilitate clinical assessment of the tissue of the subject.

2. The method of claim 1 , wherein the fluorescence agent is indocyanine green (ICG).

3. The method of claim 2 , wherein the ICG is administered at a concentration of between 25-50 mg/mL.

4. The method of claim 1 , wherein the fluorescence images are obtained at a frame rate of 20-30 frames per second.

5. The method of claim 1 , wherein the fluorescence images are obtained by a fluorescence imaging system.

6. The method of claim 5 , wherein the fluorescence imaging system comprises a laser for excitation of the ICG and a camera for capturing images of the fluorescence emitted by the ICG.

7. The method of claim 1 , wherein aggregate blood flow, F, is derived according to the formula:

F =( A )(Δ L )( P DC )/Δ t,

wherein

A is a cross-sectional area of the tissue volume end, ΔL is the derived change in the aggregate blood layer thickness, P DC is a pulse duty cycle, and Δt is a duration of a single pressure pulse.

8. The method of claim 1 , wherein the fluorescence imaging protocol further comprises administering a saline flush, following administering the fluorescence agent, to achieve a circulating peak dye concentration in excess of a predefined molar concentration.

9. The method of claim 1 , further comprising:

acquiring additional fluorescence wavelength data simultaneously with obtaining the fluorescence images; and

using the additional fluorescence wavelength data for dual-wavelength ratiometric analysis for determining an intravascular concentration of the imaging agent.

10. The method of claim 9 , wherein acquiring additional fluorescence wavelength data comprises:

measuring a fluorescence intensity signal from a first wavelength range longer than the wavelength range used for the fluorescence imaging; and

measuring a fluorescence intensity signal from a second wavelength range longer than the wavelength range used for the fluorescence imaging.

11. The method of claim 10 , wherein the first wavelength range and the second wavelength range are within the near infrared spectrum.

Assignments (18)

Cited By (4)

US 12,186,055 US 12,350,415 US 12,464,215 US 12,465,229