This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Radiology
What is meant by PET scan? 
Select and explain. 
A. Positive Emission Tomography, B. Positron Emission Tomography, C. Positron Energy Tomography, D. Positive Energy Tomography
B: Positron Emission Tomography
Answer: B: Positron Emission Tomography 
Explanation: SPECT= single photon emission computed tomography PET=positron emission tomography PET is a functional imaging technique that is used to observe metabolic processes in the body as an aid to the diagnosis of disease. The system detects pairs of gamma rays emitted indirectly by a positron-emitting radionuclide (tracer), which is introduced into the body on a biologically active moleculeThe common molecule used is fludeoxyglucose (FDG), an analogue of glucose(Ref: Grainger and Allison&;s diagnostic radiology 6th edition, page 123)