Bioluminescence imaging allows luciferase-labeled cells or genes to be imaged, following substrate (e.g. luciferin) injection, using a charge-coupled device that detects and quantifies the emitted photons. This technique offers high sensitivity due to the inherently low background noise.

Fluorescence imaging is another technique of optical imaging that utilizes fluorescently labeled molecules, including antibodies, as well as genetically induced fluorescent proteins. Compared with bioluminescence imaging, this approach uses an external light source to illuminate the animal. This in turn results in autofluorescence, which reduces the signal-to-noise ratio, compromising sensitivity.

Tissue absorption and scatter of light is, however, a limitation of optical imaging, resulting in low resolution when compared to Positron Emission Tomography, Single Photon Emission Computed Tomography, CT and MRI. Resolution is improved when near-infrared probes are used.

The Center for Molecular Imaging is acquiring a state-of-the-art optical imaging systems with high performance, including imaging in the near-infrared spectrum and fusion capabilities with CT, PET and SPECT.