Macroscopic fluorescent lifetime imaging in turbid media using angular filter arrays.

Area of Science:

• Biomedical Optics
• Medical Imaging
• Fluorescence Spectroscopy

Background:

• Detecting fluorescent agents in turbid media, like biological tissues, is challenging due to light scattering.
• Existing optical imaging methods often struggle with depth penetration and resolution in scattering environments.

Purpose of the Study:

• To develop and demonstrate an optical imaging methodology for detecting subsurface fluorophores in turbid media.
• To extract lifetime properties of fluorescent agents using the developed imaging technique.

Main Methods:

• Utilized a femtosecond pulsed laser to excite fluorophores within tissue-mimicking phantoms.
• Employed an angular filter array to collimate detected photons, accepting trajectories within 0.5 degrees of the axis.
• Used an ultra-fast gated intensified CCD camera for detecting fluorescent emission, rejecting scattered light.

Main Results:

• Achieved sub-millimeter resolution imaging up to 5 mm deep within turbid media.
• Demonstrated a large field of view, approximately 2 cm x 2 cm.
• The angular filter array's performance was independent of laser coherence or wavelength.

Conclusions:

• The developed optical imaging methodology effectively detects fluorescent agents below the surface of turbid media.
• The technique shows promise for applications requiring deep-tissue imaging and lifetime property extraction.
• The angular filter array is a key component enabling high-resolution imaging in scattering environments.