Can tissue oxidation be sensed by positronium?

Descripción del proyecto

Un salto cuántico en la detección de la pérdida de oxígeno en tejidos humanos

La hipoxia, o baja concentración de oxígeno, desempeña un papel clave en enfermedades con alta mortalidad, incluido el cáncer. Detectar con precisión la hipoxia tiene una gran importancias, ya que este proceso influye sobremanera en la progresión de la enfermedad y en los resultados del tratamiento. El objetivo del proyecto POSITRONIUM, financiado por el Consejo Europeo de Investigación, es desarrollar un nuevo sistema de tomografía para rastrear el comportamiento del positronio: un átomo de vida corta que se forma de forma natural durante las tomografías por emisión de positrones y cuyas propiedades cambian en función de los niveles de oxígeno. El equipo del proyecto estudiará si el entrelazamiento cuántico de los fotones liberados durante la desintegración del positronio puede revelar signos de hipoxia, para lo cual se cuantificará estos fotones entrelazados con un sistema de tomografía a medida.

Objetivo

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.