Deep tissue imaging by enhanced photon collection

Viera Crosignani,Sohail Jahid,Enrico Gratton,Alexander Dvornikov

doi:10.1142/s1793545814500345

Viera Crosignani, Sohail Jahid + Show 2 more

Open Access

https://doi.org/10.1142/s1793545814500345

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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.

Highlights

Biology and medical diagnostics often require imaging of deep layers of biological tissue with cellular resolution and without disrupting the physiological condition of the sample
The most common imaging systems available like confocal microscopes are only suitable for relatively transparent samples and cannot be used to access deep layer of biological tissue, which is generally strongly scattering
To assess the in-depth imaging capabilities of the DIVER, yellow-green °uorescent beads dispersed in a tissue phantom with brain-like optical properties were imaged

Summary

Introduction

Biology and medical diagnostics often require imaging of deep layers of biological tissue with cellular resolution and without disrupting the physiological condition of the sample. Deep-tissue imaging can be regarded as noninvasive \optical pathology", where all cells and molecules are observed in their intact physiological environment. The ability to image in depth is dependent on both the geometrical and optical properties of the sample, as well as the capabilities of the imaging system. The most common imaging systems available like confocal microscopes are only suitable for relatively transparent samples and cannot be used to access deep layer of biological tissue, which is generally strongly scattering. Traditional light and °uorescence microscopy, even with the aid of staining and using °uorescent markers to improve contrast, cannot image beyond 100–200 m from the surface layer of the turbid sample.[1]

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