In vivo reconstruction of NIR FRET using full-field time resolved optical tomography

摘要

We investigate the feasibility of 3-D localization of Forster resonance energy transfer (FRET) between two NIR fiuorophores (Alexa Fluor 700 and Alexa Fluor 750) in small animal models. Specifically, the decrease in donor lifetime upon FRET is used as the contrast mechanism to isolate donor-acceptor pairs undergoing FRET. The optical tomography system uses a femtosecond tunable laser coupled with a micro-mirror device based digital light processor as the source to generate wide-field patterns. The time-resolved detection is achieved using a gated intensified CCD camera. The wide-field excitation scheme described herein provides an experimental advantage by reducing the time of acquisition of temporally dense datasets. In this study, anatomical information obtained using MR imaging is used in the computation of the Monte Carlo (MC) based forward model. The MC model reconstructs the 3D distribution of the quantum yield of the donor fluorophore and the FRET complex using the time-gate data type allowing the estimation of fractional distribution (f_d) of donor molecules undergoing FRET and unquenched donor molecules. The performance of this approach in the estimation of f_D using the position of fiuorophores obtained using the MRI is investigated.