Comparison of illumination geometry for lifetime-based measurements in whole-body preclinical imaging.

Macroscopic fluorescence lifetime imaging (MFLI) has been proved to be an accurate tool to quantify Förster resonance energy transfer (FRET) lifetime-based assessment of receptor-ligand engagement in vitro and in vivo. Herein, we report on the quantitative comparison of MFLI for whole-body preclinical studies in transmittance and reflectance geometries. The comparative study was conducted for both in vitro and in vivo conditions. FRET quantification performance in both geometries was similar in high fluorescence concentration samples. However, the reflectance geometry performed better at low fluorescence concentration. In addition, reflectance geometry could acquire subsurface imaging of the main whole-body organs of small animals without being compromised by tissue attenuation.