Figure 1.

Schematic of ¹⁸FDG-PET imaging principles. (a) ¹⁸FDG production step 1: ¹⁸O enriched water (95%) is bombarded with protons in a cyclotron creating 18-flouride (¹⁸F) which is purified on a resin column and rinsed with potassium carbonate. Step 2: ¹⁸F is added with Kryptofix2.2.2 to the precursor glucose starting material and through a nucleophilic substitution, subsequent purification and removal of protecting groups, ¹⁸FDG is synthesized. (b) The radiotracer accumulates in tissue where it is transported into metabolically active cells, metabolized by hexokinase, and trapped as FDG-6-phosphate, as it is not a good substrate for further metabolism by glucose phosphate isomerase (GPI). (c) Representation of a mouse in the field of view of a small animal PET camera. When the ¹⁸F on a molecule of ¹⁸FDG undergoes beta decay, a proton turns into a neutron expelling a positron and neutrino from the atomic nucleus. The positron travels up to a few millimeters before it collides with an electron (inset). The energy of this annihilation expels 2 511 keV gamma rays (γ) approximately 180° apart from each other. These γ rays are detected simultaneously by a ring of LSO crystals that make up the PET camera.