Exploration of X-ray Fluorescence Emission Tomography for Imaging Micro-Scintillators used in Remote Optogenetics Application

Optogenetics is a biological technique which aims to modulate the neuronal activities of target cells through activation of light-sensitive proteins. X-ray induced optogenetics is an approach to generate visible light in deep tissues using radioluminescence of scintillating micro-particles through x-ray irradiation. The increase in the penetration depth, reduction in tissue heating, and absence of invasive surgical procedure are the major advantages of x-ray induced optogenetic approach. Previous studies have shown that Ce:GAGG (Ce: Gd
3
Al
2
Ga
3
O
12
) scintillating particles/crystals are biocompatible and non-cytotoxic with one of the brightest light yield which makes them a suitable candidate for X-Optogenetics. In this study, we demonstrate the feasibility of imaging Ce:GAGG micro-scintillating particles in mouse brain and gut region using our full-ring benchtop x-ray fluorescence emission tomography (XFET) system. Our preliminary experimental studies with pulverized Ce:GAGG micro-particles demonstrate an excellent detection limit of 14 mg in a small animal-sized phantom. We would further explore the improvement in signal-to-noise ratio and detection limit for remote optogenetic application by preparing a GEANT4 model of the multi-slit XFET system and simulating for different source configurations and detection angles.