Effective Rapid Fluorescence Lifetime Imaging of the Brain: A Novel Approach Using Upconversion Photoluminescence Lifetime Based on Gate-Width Acquisition.

The rapid lifetime imaging of upconversion photoluminescence is becoming increasingly popular in biosensing, anticounterfeiting, optical thermometry, and multiplex imaging. However, existing Rapid Lifetime Determination (RLD) techniques are limited in their ability to integrate contiguous, overlapping, and discrete windows into a single measurement, hindering accurate fluorescence lifetime retrieval. This study introduces a new data acquisition method using three adjustable gates in a single measurement to enhance resolution. We apply this method in rapid upconversion fluorescence lifetime imaging to visualize capillary networks and map pH levels based on intensity and lifetime differences in mouse brain vasculature. By enhancing brightness using NaYbF4@NaYF4,Er,Tm@NaYF4 nanoparticles, we achieve effective brain imaging. Monte Carlo simulations demonstrate a relative standard deviation of less than 0.4% for fluorescence durations spanning from 1 to 20 ns. This method provides a fast, high-contrast solution for multiplex brain imaging, addressing the limitations of slow data collection and poor accuracy in existing RLD techniques.