Seminaria Instytutowe

Positronium Imaging with the J-PET scanner

by Paweł Moskal (IF UJ)

The modern medicine, developing towards personalized treatment of patients, requires high specificity in assessing the disease. Our research aims at improvement of specificity of the PET diagnosis by use of positronium as a theranostic agent. During the positron emission tomography about 40% of positrons annihilations occur through the creation of positronium. Positronium is formed in human tissues in intramolecular spaces, as exotic atom composed of an electron from tissue and a positron emitted by a radioisotop.  Positronium decays in the patient body are sensitive to the nanostructure and metabolism of the tissues. This phenomenon is not used in the present PET diagnostics, yet it is in principle possible to use environment modified properties of positronium as diagnostic biomarkers for cancer therapy. First in-vitro studies show differences of positronium mean lifetime and production probability in the healthy and cancerous tissues, indicating that they may be used as indicators for in-vivo cancer classification. For the application in medical diagnostics the properties of positronium atoms need to be determined in a spatially resolved manner. For that purpose we developed a method of positronium lifetime imaging in which the lifetime and position of positronium atoms is determined on an event-by-event basis. The method requires application of β+ decaying isotope emitting prompt gamma. We will argue that with the total-body PET scanners the sensitivity of the positronium lifetime imaging, which requires coincident registration of the back-to-back annihilation photons and the prompt gamma is comparable to the sensitivities for the metabolic imaging with standard PET scanners.
P. Moskal et al., Nature Reviews Physics 1 (2019) 527.
J-PET: P. Moskal et al., Nature Communication 12 (2021) 5658.
J-PET: P. Moskal et al., Science Advances 7 (2021) eabh4394.