
Positron Emission Tomography (PET) is a key technique in the medical imaging area, which allows to diagnose the organism functions and to track the tumor changes. In PET measurement the patient is injected with radiotracer, containing a large number of metastable atoms of radionuclide, that emmits positrons. As the result of positron annihilation, the two photons travelling off with nearly opposite directions are produced and registered by detection system positioned so that it surrounds the patient body. State-of-the-art PET scanners use scintillation crystals which are characterized by high detection efficiency of annihilation photons. In this context, it is worth to mention that the Jagiellonian PET (J-PET) Collaboration developed a novel whole-body PET scanner based on plastic scintillators. They are much cheaper than crystal scintillators, which gives the opportunity to reduce the high cost of PET scanners and make them more affordable. However, plastic scintillators have much low