Positronium: Review of symmetry, conserved quantities and decay for the radiological physicist

Harpen, Michael D.

doi:10.1118/1.1630494

Cited by 68 publications

(67 citation statements)

References 14 publications

(15 reference statements)

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“…Even larger deviations from 1801 and 511 keV are expected from longer runs (more radiation histories). Note that positrons annihilating at 1.58 MeV violate the kinetic energy 5m o c 2 condition used by Harpen to estimate the angular spread [13]. Our work simulated neither non-zero electron momentum nor positronium formation, which are not available in the Monte Carlo codes considered.…”

Section: Annihilation Under Pet Conditionsmentioning

confidence: 93%

Monte Carlo investigation of positron annihilation in medical positron emission tomography

Chin¹,

Spyrou²

2007

Nuclear Instruments and Methods in Physics Research Section A:

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Section: Annihilation Under Pet Conditionsmentioning

confidence: 93%

Monte Carlo investigation of positron annihilation in medical positron emission tomography

Chin¹,

Spyrou²

2007

Nuclear Instruments and Methods in Physics Research Section A:

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“…The observed lifetime of o-Ps in liquids is considerably shorter than its vacuum value due to pick-off effect, where a second electron with opposed spin reacts with the positron in the o-Ps atom resulting in two photon annihilation. The observed lifetime of o-Ps in water is 1800 ps, shorter than the vacuum lifetime of 140 ns (Westbrook et al 1989), but much longer than p-Ps lifetime, thus we may conclude that most annihilations in tissue result in two-gamma ray emissions despite the larger amount (3:1) of o-Ps initially formed (Harpen 2004).…”

Section: Positron Annihilationmentioning

confidence: 96%

“…Para-positronium decays only into two photons, while ortho-positronium decays into three (Harpen 2004). The fraction of positrons forming positronium is known as the Ps yield.…”

Section: Positron Annihilationmentioning

confidence: 99%

Positron range estimations with PeneloPET

Cal-González

Herraiz²,

España

et al. 2013

Phys. Med. Biol.

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Technical advances towards high resolution PET imaging try to overcome the inherent physical limitations to spatial resolution. Positrons travel in tissue until they annihilate into the two gamma photons detected. This range is the main detector-independent contribution to PET imaging blurring. To a large extent, it can be remedied during image reconstruction if accurate estimates of positron range are available. However, the existing estimates differ, and the comparison with the scarce experimental data available is not conclusive. In this work we present positron annihilation distributions obtained from Monte Carlo simulations with the PeneloPET simulation toolkit, for several common PET isotopes ( 18 F, 11 C, 13 N, 15 O, 68 Ga and 82 Rb) in different biological media (cortical bone, soft bone, skin, muscle striated, brain, water, adipose tissue and lung). We compare PeneloPET simulations against experimental data and other simulation results available in the literature. To this end the different positron range representations employed in the literature are related to each other by means of a new parameterization for positron range profiles. Our results are generally consistent with experiments and with most simulations previously reported with differences of less than 20% in the mean and maximum range values. From these results, we conclude that better experimental measurements are needed, especially to disentangle the effect of positronium formation in positron range. Finally, with the aid of PeneloPET, we confirm that scaling approaches can be used to obtain universal, material and isotope independent, positron range profiles, which would considerably simplify range correction.

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“…The ortho-positronium triplet (o-Ps) and para-positronium singlet (p-Ps) states can be distinguished and their spin alignment determines their properties. Due to the charge conjugation conservation, the o-Ps can decay only into odd number of photons, while the p-Ps decays into even number of photons, and the mean lifetime of o-Ps state in vacuum is longer (140 ns [5]) than that for p-Ps state (120 ps [5]). …”

Section: Introductionmentioning

confidence: 99%

Searches for discrete symmetries violation in ortho-positronium decay using the J-PET detector

et al. 2015

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Abstract. In this paper, we present prospects for using the Jagiellonian positron emission tomograph (J-PET) detector to search for discrete symmetries violations in a purely leptonic system of the positronium atom. We discuss tests of CP and CPT symmetries by means of ortho-positronium decays into three photons. No zero expectation values for chosen correlations between ortho-positronium spin and momentum vectors of photons would imply the existence of physics phenomena beyond the standard model. Previous measurements resulted in violation amplitude parameters for CP and CPT symmetries consistent with zero, with an uncertainty of about 10. The J-PET detector allows to determine those values with better precision, thanks to the unique time and angular resolution combined with a high geometrical acceptance. Achieving the aforementioned is possible because of the application of polymer scintillators instead of crystals as detectors of annihilation quanta.

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Positronium: Review of symmetry, conserved quantities and decay for the radiological physicist

Cited by 68 publications

References 14 publications

Monte Carlo investigation of positron annihilation in medical positron emission tomography

Monte Carlo investigation of positron annihilation in medical positron emission tomography

Positron range estimations with PeneloPET

Searches for discrete symmetries violation in ortho-positronium decay using the J-PET detector

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