**Core Concept:** Positron Emission Tomography (PET) scan is a nuclear medicine imaging technique used to visualize the physiological processes within the body at the cellular level. It detects the emission of positrons from radioactive tracer materials that are injected into the patient's bloodstream and bind to specific cellular targets.

**Why the Correct Answer is Right:** A PET scan uses a radioactive tracer material called Fluorodeoxyglucose (FDG). FDG is an analogue of glucose, the body's primary energy source, and is taken up by cells through glucose transporters. Inside the cell, FDG is phosphorylated by hexokinase to form FDG-6-phosphate, which accumulates in cells with high levels of glucose utilization, such as cancer cells, inflammatory cells, and activated neurons. By detecting the emitted positrons, PET scan can visualize these high glucose-utilizing areas in the body, providing valuable information about cellular processes.

**Why Each Wrong Option is Incorrect:**

A. Positron Emission Tomography scan also uses other tracer materials, but FDG is by far the most commonly used. Options A, B, and C are incorrect because they represent other tracer materials that are not commonly used in PET scans.

B. While some PET scans use amino acids for imaging specific neurological processes, option B is incorrect as it does not represent the most common tracer material used in PET scans.

C. Option C refers to Technetium-99m, an isotope often used in Single Photon Emission Computed Tomography (SPECT) scans, not PET scans.

D. Some PET scans use Fluorine-18, but FDG is by far the most common tracer material used in PET scans.

**Clinical Pearl:** Fluorodeoxyglucose (FDG) is the most commonly used tracer material in PET scans for its ability to visualize areas of high glucose utilization, such as tumors, inflammation, and neurological disorders. This information is crucial for interpreting PET scan results accurately and understanding the functional anatomy of the body.