Positron Emission Tomography (PET)
Here's your citation in American Psychological Association (APA) format:
Positron Emission Tomography (PET). (n.d.). In Alleydog.com's online glossary. Retrieved from: https://www.alleydog.com/glossary/definition-cit.php?term=Positron+Emission+Tomography+%28PET%29