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How Does PET Work?

In positron emission tomography (PET), a weak radioactive substance – known as a radiotracer – generates the signal. Patients receive an injection of this substance before measurements are taken. These radiotracers travel to the brain via the bloodstream and accumulate in specific cells depending on the type of tracer: sugar molecules, for example, accumulate where an increased energy demand exists and neurotransmitters at the corresponding receptors.

The decay products of the radioactive substance provide information on the processes investigated. When radioactive atoms decay spontaneously in the tracer, positrons are produced. When these positrons hit electrons, a measurable signal is generated (two gamma rays). With a resolution of a few millimetres, they show where the radiotracer was involved in molecular processes.

In this way, brain activities and metabolic processes can be observed, as can tumour tissue or receptors that are responsible for the communication between brain cells.
In order to investigate such processes in the brain, tailor-made radiotracer must be available. Jülich researchers at the Institute of Nuclear Chemistry are therefore developing and testing these.