ABSTRACT
Preclinical imaging is a powerful tool to enhance the ways in which biological processes are studied. Quantification is referred to as a numerical expression of concentration. Optical and nuclear modalities (single photon emission computerized tomography [SPECT] and positron emission tomography [PET]) provide primarily functional information; in these techniques, a tracer or imaging agent is injected into the animal and the regional concentration is investigated. In nuclear imaging modalities, the acquisition process has no impact on the underlying processes of radioactive decay. One of the main differences between clinical and preclinical imaging is the requirement for animal anesthesia in most cases. Anesthesia is typically administered via intravenous injection or inhalation. Depth of anesthesia can be approximated by monitoring respiration rate and rectal body temperature. Tracer administration may have a significant impact on the physiology of the animal. Most technological issues regarding the quantification of SPECT and PET, as well as correction strategies, may be similar.
