A Comparison Between Time Domain and Spectral Imaging Systems for Imaging Quantum Dots in Small Living Animals
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We quantified the performance of time-domain imaging (TDI) and spectral imaging (SI) for fluorescence imaging of quantum dots (QDs) in three distinct imaging instruments: eXplore Optix (TDI, Advanced Research Technologies Inc.), Maestro (SI, CRi Inc.), and IVIS-Spectrum (SI, Caliper Life Sciences Inc.).
The instruments were compared for their sensitivity in phantoms and living mice, multiplexing capabilities (ability to resolve the signal of one QD type in the presence of another), and the dependence of contrast and spatial resolution as a function of depth.
In phantoms, eXplore Optix had an order of magnitude better sensitivity compared to the SI systems, detecting QD concentrations of ~40 pM in vitro. Maestro was the best instrument for multiplexing QDs. Reduction of contrast and resolution as a function of depth was smallest with eXplore Optix for depth of 2–6 mm, while other depths gave comparable results in all systems. Sensitivity experiments in living mice showed that the eXplore Optix and Maestro systems outperformed the IVIS-Spectrum.
TDI was found to be an order of magnitude more sensitive than SI at the expense of speed and very limited multiplexing capabilities. For deep tissue QD imaging, TDI is most applicable for depths between 2 and 6 mm, as its contrast and resolution degrade the least at these depths.
Key wordsTime-domain imaging Frequency-domain imaging Quantum dots imaging Optical tomography Small animal imaging Molecular imaging
We acknowledge funding support from the National Institute of Health grants NCI CCNE U54 CA119367 (SSG), NCI ICMIC P50 CA114747 (SSG) and the Canary Foundation (SSG). A. de la Zerda thanks the Bio-X Graduate Student Fellowship and the DoD Breast Cancer Research Program - Predoctoral Traineeship Award for partially supporting this work.
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