title: A comparison between time domain and spectral imaging systems for imaging quantum dots in small living animals.
abstract: OBJECTIVE
  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.).
  
  
  METHODS
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Radiology, Molecular Imaging Program at Stanford (MIPS), The Bio-X Program, Stanford, CA 94305, USA.
authors.forename: Adam
authors.initials: A
authors.lastname: de la Zerda
authors.forename: Sunil
authors.initials: S
authors.lastname: Bodapati
authors.forename: Robert
authors.initials: R
authors.lastname: Teed
authors.forename: Meike L
authors.initials: ML
authors.lastname: Schipper
authors.forename: Shay
authors.initials: S
authors.lastname: Keren
authors.forename: Bryan R
authors.initials: BR
authors.lastname: Smith
authors.forename: Johnny S T
authors.initials: JS
authors.lastname: Ng
authors.forename: Sanjiv Sam
authors.initials: SS
authors.lastname: Gambhir
mesh_terms: D000818:Animals; D005453:Fluorescence; D051379:Mice; D045663:Quantum Dots