Mini-review on the temporal resolution of fluorescence imaging systems

TL;DR

This review explores the limits of temporal resolution in fluorescence imaging, deriving an estimate based on molecular relaxation times and discussing advanced microscopy techniques capable of high temporal resolution.

Contribution

It provides an analytical estimate for the temporal resolution limit of fluorescence imaging systems and discusses microscopy techniques that achieve high temporal resolution.

Findings

Derived an expression for the relaxation time limit based on emission rates

Identified microscopy techniques capable of high temporal resolution

Assumed ideal conditions for the estimation

Abstract

Imaging of rapidly occurring events in biology requires high temporal resolution. In this review article, I have tried to investigate an approximate estimate to quantify temporal resolution limit of a fluorescence imaging system. It was realised that, the temporal resolution is essentially determined by the fact that, once excited, almost all ($99.9\%$) excited molecules relax to ground state. We determined the time required for $99.9\%$ of molecules to relax is about $3\tau_p = 3/{(k_f +k_{nr})\log_{10}e}$, where $k_f +k_{nr}$ is the total emission rate. To arrive at this expression we assumed that, the quantum efficiency of the detector is unity, no scattering and there are no other loses. We further discuss few microscopy technique that are capable of high temporal resolution. These technique includes, multifocal multiphoton microscopy (MMM), multiple excitation spot optical microscopy (MESO) and multiple light-sheet microscopy (MLSM).