METHOD OF DEEP TISSUE IMAGING USING MULTI-PHOTON EXCITATION OF A FLUOROPHORE

摘要

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.

主权项

1. 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, the step of irradiating being performed with a laser with at least picosecond or faster 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 between about 650 nm and about 1100 nm; andan excited singlet energy gap (S0 to Sn where n is greater than 1) corresponding to the multi-photon excitation wavelength that is within an 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; permitting the excited singlet state (Sn) to undergo non-radiative relaxation to the first singlet state (S1); permitting the first singlet state (S1) 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 to produce an image of the biological tissue.