Time-resolved mesoscopic imaging of a whole animal by FastFLIM

The mesoscopic scale is between microscopic and macroscopic scales. In life sciences, mesoscopic imaging allows scientists to record, track and study details of biological systems in the context of an organ, body part, or organism. Mesoscopic imaging techniques have been developed for medical and clinical research, such as drug delivery, cancer diagnosis, etc. Especially when combined with novel nanoparticles and organic dyes in the near-infrared spectral regime, the mesoscopic imaging can probe deeper parts of the animal body. Here, we describe a timeresolved mesoscopic imaging approach, which can image deep inside of the whole mouse noninvasively. In addition, it uses the FastFLIM technique to measure the lifetime of the fluorescent probe. Since the lifetime carries information about the probe's local microenvironment such as temperature, pH, ion concentration, etc., the lifetime imaging map obtained by the FastFLIM-mesoscope allows tracking quantitative dynamics of the probes in the whole animal body. The technique can also be used for quantitative intrinsic NADH metabolism mapping for real time monitoring of mitochondrial function. Here, we will show mesoscopic-scale NADH imaging in an oral cancer model.