Which of the following techniques uses radioactive tracers like [18F]FDG?
Positron emission tomography fundamentally depends on positron-emitting tracers chemically identical to normal physiological substrates. Fluorine-18 labeled fluorodeoxyglucose, [18F]FDG, mimics glucose, enters cells via glucose transporters and is phosphorylated by hexokinase, then becomes metabolically trapped because deoxy modification prevents further glycolysis and egress. Accumulation rate directly reflects regional glucose consumption, high in active cortex, language areas, epileptic foci interictally or tumors. Magnetic resonance uses proton signals, CT uses X-ray attenuation, EEG measures voltage, only PET routinely employs radioactive tracers like FDG for metabolic imaging.
Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.