Method of deep tissue imaging using multi-photon excitation of a fluorophore
AssigneeResearch Foundation of the City University of New York
InventorsRobert R. Alfano, Yang Pu, Lingyan Shi, Sebastião Pratavieira
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Abstract
A method is provided for deep tissue imaging using multi-photon excitation of a fluorescent agent. The fluorescent agent is irradiated with an ultrafast laser to produce an excited singlet state (Sn) which subsequently undergoes non-radiative relaxation to a first singlet state (S1). The S1 state undergoes fluorescence to the ground state S0 to produce an emission wavelength. Both the excitation and emission wavelengths are within the near infrared optical window, thereby permitting deep tissue penetration for both the incoming and outgoing signals.
Claims22
A method for imaging tissue using a multi-photon process where both excitation and emission wavelengths fall within an optical window, the method comprising sequential steps of:
- irradiating a fluorescent agent with a multi-photon excitation wavelength that is within the optical window, wherein the optical window is selected from a group consisting of:
- a first optical window at 650±25 nm to 1100±25 nm;
- a second optical window at 1200±25 nm to 1350±25 nm;
- and
- a third optical window at 1550±25 nm to 1800±25 nm;
- the step of irradiating being performed with a laser with picosecond pulses,
- the fluorescent agent being present within a biological tissue and having:
- a first singlet energy gap (S0 to S1) corresponding to an emission wavelength within the optical window;
- and
- an excited singlet energy gap (S0 to Sn where n is greater than 1) corresponding to the multi-photon excitation wavelength that is within the optical window, the step of irradiating producing an excited singlet state (Sn) that is higher in energy than a first singlet state (S1) of the fluorescent agent;
- allowing time to pass such that the excited singlet state (Sn) is permitted to undergo non-radiative relaxation to the first singlet state (S1);
- allowing time to pass such that the first singlet state (S1) is permitted to undergo fluorescence to a ground state (S0) to produce the emission wavelength that is within the optical window, the emission wavelength corresponding to the first singlet energy gap (S0 to S1);
- and
- imaging the biological tissue using the emission wavelength to produce an image of the biological tissue.
A method for imaging tissue using a multi-photon process where both excitation and emission wavelengths fall within an optical window of 700±25 nm to 900±25 nm, the method comprising sequential steps of:
- providing indocyanine green (ICG) to a biological tissue;
- irradiating the ICG with a multi-photon excitation wavelength of 800 nm, the step of irradiating being performed with a laser with picosecond pulses, the ICG being present within a biological tissue and having:
- a first singlet energy gap (S0 to S1) corresponding to an emission wavelength of 685 nm;
- and
- an excited singlet energy gap (S0 to Sn where n is greater than 1) corresponding to the multi-photon excitation wavelength of 800 nm that is within the optical window, the step of irradiating producing an excited singlet state (Sn) that is higher in energy than a first singlet state (S1) of the ICG;
- allowing time to pass such that the excited singlet state (Sn) is permitted to undergo non-radiative relaxation to the first singlet state (S1);
- allowing time to pass such that the first singlet state (S1) is permitted to undergo fluorescence to a ground state (S0) to produce the emission wavelength, the emission wavelength corresponding to the first singlet energy gap (S0 to S1);
- and
- imaging the biological tissue using the emission wavelength of 685 nm to produce an image of the biological tissue.
Dependencies are inferred from the claim text.