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The three-photon yield from e+ annihilation in various fluids.

K Mercurio·P Zerkel·R Laforest·L G Sobotka·R J Charity
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Abstract

Positronium in the triplet state decays by the emission of three photons and it has been proposed that their simultaneous detection can be used for medical imaging. The three-photon yield has been observed to be enhanced in low O(2) levels in some fluids but has never been measured in biologically relevant liquids. In this study, the delayed three-photon decay yield, at both high and low O(2) levels, has been extracted by fitting the time dependence of the two-photon yield to a set of coupled differential equations. The differential equations, in a simple yet seemingly satisfactory fashion, account for the e(+) capture to form positronium, its decay and the interconversion of the two spin configurations. Our results indicate that the delayed three-photon fraction is 0.25% in water (or blood-like) samples and exhibits no (or exceedingly small) dependence on the dissolved oxygen content. If one assumes that the direct component contributes a fraction expected by annihilation on free electrons (1/372), then the total three-photon fraction is 0.52% in the samples of biological relevance.

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AlgorithmsBody FluidsComputer SimulationElectronsHumansOxygenPhotonsRadiographyRadiotherapy, ConformalTime FactorsJournal ArticleResearch Support, N.I.H., ExtramuralResearch Support, U.S. Gov't, Non-P.H.S.

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K Mercurio, P Zerkel, R Laforest, L G Sobotka, R J Charity. 2006-08-15. The three-photon yield from e+ annihilation in various fluids.. https://doi.org/10.1088/0031-9155%2F51%2F17%2Fn05

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