POSITRONIUM · Can tissue oxidation be sensed by positronium?

A method for non-invasive assessment of hypoxia (deficit of oxygen in tissue) is keenly awaited in medicine. This project is motivated by the exciting question whether it is possible to assess the concentration of oxygen in the tissue by detecting photons from positronium decays inside cells. Positronium (a bound state of an electron and positron) is copiously produced in the human body during positron emission tomography. Its properties in tissue depend on the size of the intramolecular voids and the concentration of molecular oxygen. Thus, it is plausible to expect that positronium may serve as a biomarker of tissue oxidation. Yet is this really the case? Is it at all possible to disentangle annihilation of positronium after it interacted with oxygen from the annihilation with electrons from the tissue’s atoms? This question has no a priori answer because the number of classical observables accessible by the measurement of annihilation photons is less than the number of mechanisms leading to positron annihilation in the tissue.Here we put forward the fundamentally new hypothesis that tissue oxidation may be sensed by the measurement of the degree of entanglement of photons from positronium. Theoretically, these photons are quantum entangled in polarization and exhibit non-local correlations. The entanglement is reflected in the distribution of relative angle between photons’ polarization planes. We hypothesize that such distributions are sensitive to tissue hypoxia. This leads to the expectation that the degree of entanglement for photons from positronium interacting with dissolved oxygen differs from the case when it annihilates by picking-off an electron from a molecule. Answers to these fundamental questions will be delivered for the first time. The project will be implemented by using a unique tomography system invented by the PI facilitating imaging of positronium lifetime and detecting the polarization of photons from the positronium annihilation.