Spatially resolved measurements of ballistic and total transmission in microscale tissue samples from 450 nm to 1624 nm

We built a simple and versatile setup to measure tissue ballistic and total transmission with customizable wavelength range, spatial resolution, and sample sizes. We performed ballistic transmission and total transmission measurements of overlying structures from biological samples ex vivo. We obtained spatially resolved transmission maps to reveal transmission heterogeneity from five microscale tissue samples: Danionella skin, mouse skull bone, mosquito cuticle, wasp cuticle, and rat dura over a wide spectral range from 450 nm to 1624 nm at a spatial resolution of similar to 25 mu m for ballistic transmission measurements and similar to 50 mu m for total transmission measurements. We expect our method can be straightforwardly applied to measuring the transmission of other samples. The measurement results will be valuable for multiphoton microscopy. The total transmission of a sample is important for the collection of multiphoton excited fluorescence and the assessment of laser-induced sample heating. The ballistic transmission determines the excitation power at the focus and hence the fluorescence signal generation. Therefore, knowledge of ballistic transmission, total transmission, and transmission heterogeneity of overlying structures of animals and organs are essential to determine the optimal excitation wavelength and fluorophores for non-invasive multiphoton microscopy. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement