Q.Explain the principle involved in PET scan

Step 1. PET (positron emission tomography) is a nuclear-medicine technique based on measuring positron emission from a radiolabelled tracer molecule introduced into the body, rather than on transmitting radiation through the body from an external source.

Step 2. The tracers are built using positron-emitting radioisotopes - such as carbon-11, nitrogen-13, oxygen-15 and fluorine-18 - generated in a cyclotron; these radioactive atoms are chemically incorporated into biological molecules such as glucose, amino acids or ammonia, with 18F-fluorodeoxyglucose (18F-FDG), a radiolabelled sugar, being the most widely used tracer.

Step 3. A very small amount of the labelled compound is injected into, or inhaled by, the patient, and as it distributes and is taken up by tissues according to their metabolic activity, it continues to emit positrons as it decays. …

Explain PET's core principle: an injected positron-emitting radiotracer, its tissue uptake reflecting metabolism, and came …

• Describing PET as if it transmits radiation through the body like an X-ray, instead of detecting radiation emitted from an internally injected tracer. …