ABSTRACT
Imaging with non-ionizing photons in the visible and infrared regions of the electromagnetic spectrum is a firmly established method in preclinical imaging. The advantages of optical imaging include excellent sensitivity, good contrast, lower cost, and the use of non-ionizing radiation. In general, however, optical imaging suffers from poor resolution, even in comparison with other high-sensitivity modalities in nuclear medicine imaging. Optical imaging can be classified into a variety of families. The most interesting classification of optical imaging mirrors those in clinical imaging: that is, the distinction between transmission and emission imaging. Emission imaging encompasses the passive modalities that capture photons generated inside the body via the conversion of energy from other sources to optical light. Frequency-domain imaging is commonly utilized in transmission optical imaging modalities such as diffuse optical imaging and tomography and fluorescence molecular tomography. Time-domain optical imaging is both the most technically challenging and expensive form of transmission optical imaging.
