In vivo imagers, sometimes called preclinical imaging systems, are imaging systems that look deep into the tissues of living subjects. The benefits of this type of system are that it gives the most complete picture of the biological effects of a treatment or disease progression and the animal is kept alive allowing future analysis on the same subject. An imager consists of three components: a box to hold the animal, the imager itself, and a computational system for analyzing the data. It is common for subjects to also be administered non-toxic dyes or probes to facilitate targeted tissue imaging. Lab imagers can be mini versions of clinical tools such as MRI, CT, PET, and SPECT or fluorescence or bioluminescence optical imaging systems that are only used in the lab; modern systems often employ more than one of these imaging types. Determining what needs to be imaged, the level of detail desired, and price point are all important to consider when purchasing an in vivo imager.