Deep tissue imaging by enhanced photon collection

Abstract

We have developed a two-photon fluorescence microscope capable of imaging up to 4mm in turbid media with micron resolution. The key feature of this instrument is the innovative detector, capable of collecting emission photons from a wider surface area of the sample than detectors in traditional two-photon microscopes. This detection scheme is extremely efficient in the collection of emitted photons scattered by turbid media which allows eight fold increase in the imaging depth when compared with conventional two-photon microscopes. Furthermore, this system also has in-depth fluorescence lifetime imaging microscopy (FLIM) imaging capability which increases image contrast. The detection scheme captures emission light in a transmission configuration, making it extremely efficient for the detection of second harmonic generation (SHG) signals, which is generally forward propagating. Here we present imaging experiments of tissue phantoms and in vivo and ex vivo biological tissue performed with this microscope.