318 Campus Drive
Palo Alto
CA 94305
2:00-2:45 PM | Prof. Pawel Moskal
“Positronium Imaging with the J-PET Scanner”
Head of the Department of Experimental Particle Physics and Applications Marian Smoluchowski Institute of Physics
Jagiellonian University, Poland
2:45-3:00 PM | Prof. Ewa Stepien
“Preclinical studies of positronium and extracellular vesicles biomarkers”
Head of the Department of Medical Physics
Marian Smoluchowski Institute of Physics
Jagiellonian University, Poland
Abstract
As modern medicine develops towards personalized treatment of patients, there is a need for highly specific and sensitive tests to diagnose disease. Our research aims at improvement of specificity of positron emission tomography (PET) in assessment of cancer by use of positronium as a theranostic agent. During PET scanning about 40% of positron annihilations occur through the creation of positroni-um. “Positronium,” which may be formed in human tissues in the intramolecular spaces, is an exotic atom composed of an electron from tissue and the positron emitted by the radioinuclide. Positronium decay in the patient body is sensitive to the nanostructure and metabolism of human tissues. This phenomenon is not used in present PET diagnostics, yet it is in principle possible to exploit such envi-ronment modified properties of positronium as diagnostic biomarkers for cancer assessment. Our first in-vitro studies have shown differences of the positronium mean lifetime and production probability in healthy and cancerous tissues, indicating that they may be used as indicators for in-vivo cancer classifi-cation. For the application in medical diagnostics, the properties of positronium atoms need to be determined in a spatially resolved manner. For that purpose we have developed a method of positroni-um lifetime imaging in which the lifetime and position of positronium atoms are determined on an event-by-event basis. This method requires application of β+ decaying isotope that also emits a prompt gamma ray. We will argue that with total-body PET scanners, the sensitivity of positronium lifetime imaging, which requires coincident registration of the back-to-back annihilation photons and the prompt gamma, is comparable to the sensitivities for metabolic imaging with standard PET scanners.
Our research involves also development of diagnostic methods based on the extracellular vesicles (EVs), which are micro and nano-sized, closed membrane fragments. They are produced by native cells to facilitate the transfer of different signaling factors, structural proteins, nucleic acids or lipids even to distant cells. They are present in all body fluids and they are specific to their parental cells.
Our presentation will be divided into two parts. In the first, the method of positronium imaging and the pilot positronium images obtained with the J-PET detector (the first PET system built based on plastic scintillators) will be reported. This part of the presentation will include also description and perspec-tives of development of the J-PET technology in view of total-body PET imaging. The second part will concern preliminary results of the preclinical studies of positronium properties in cancerous and healthy tissues sampled from patients as well as in the frozen and living healthy and cancer skin cells in-vitro. The second part will include also description of the novel method for the diagnosis of diabetes and melanoma based on EVs used as biomarkers and drug delivery systems.