Calibration of PALS System withCRM Materials for BiomedicalStudies

<b>Objective and method:</b> Positron annihilation lifetime spectroscopy (PALS) is a powerfultechnique in material science that allows the investigation of the properties andbehavior of positrons in various materials. PALS can be used to investigate solidstructures at the nanometer scale and enable the use of positronium properties as anadditional diagnostic parameter. Here we present results from calibration of the PALSsystem with certificated reference materials (CRM).<b>Materials:</b> Source of <sup>22</sup>Na covered with layer of Kapton film, and after that parafilm from both sides was used in all experiments. Certified materials of No_5602-a (polycarbonate) and No_5601-a (fused silica) were used to ascertain if parameters were correctly identified.<b>Results:</b> In an experiment three lifetime components were correctly identified. All of those components will always be present in the data in further experiments on biological samples. Lifetime components consist of: 196 ps for annihilations in AI an aluminium cover of the chamber, 386 ps for annihilations in thesource and in the Kapton foil, 463 ps for reactions with parafilm.<b>Conclusions:</b> These parameters will be further used to correctly identify positronlifetimes in biological samples. Recently, a new method for imaging of positroniumproperties was invented and the first in-vivo images of positronium lifetime in humanswere demonstrated with the multi-photon J-PET scanner. In order to correlate thepositronium properties in tissue with the medically useful parameters, and to translatepositronium imaging to clinics, comprehensive research of positronium properties inbiological samples is needed.