Positron Age-Momentum-Correlation (AMOC) Measurements on Organic Liquids

Castellaz, P.; Siegle, A.; Stoll, Hermann

doi:10.14494/jnrs2000.3.2_r1

Cited by 13 publications

(16 citation statements)

References 12 publications

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“…The Ps yield in water was found to be 38% and in other liquids ͑organic solvents͒ as high as 70% in spite of positron recoil effects at the liquid surface. It seems reasonable to expect the yield from lower energy sources embedded in tissue, as in PET, to be higher than the 38% for water 15 due to the lack of surface effects and the lower instance of in-flight annihilation.…”

Section: Discussion: Positrons In Tissuementioning

confidence: 99%

“…The fraction of positrons forming Ps is the Ps yield. Using the technique of Positron Age-Momentum-Correlation ͑AMOC͒ Castellaz et al 15 have measured the Ps yields in a variety of liquids for an external 4 MeV positron beam. The Ps yield in water was found to be 38% and in other liquids ͑organic solvents͒ as high as 70% in spite of positron recoil effects at the liquid surface.…”

Section: Discussion: Positrons In Tissuementioning

confidence: 99%

“…Assuming that all spin states for electrons and positrons are equally probable we should expect o-Ps and p-Ps to be produced in the ratio 3:1 and this is in fact observed in liquids. 15 Once formed p-Ps is observed to decay in liquids with its vacuum lifetime ϳ125 ps. The observed lifetime of o-Ps in liquids is considerably shorter than its vacuum value due to pick-off annihilation where a second electron with opposed spin reacts with the positron in th o-Ps atom resulting in a two photon annihilation.…”

Section: Discussion: Positrons In Tissuementioning

confidence: 99%

“…Using the AMOC technique Castellaz et al 15 have observed that in solutions ''early'' Ps decays, i.e., those of p-Ps, have significantly more Doppler broadening of the annihilation spectrum than late decays, i.e., o-Ps decays. This indicates considerably more residual momentum in p-Ps at the time of decay and that the noncollinearity of annihilation radiation in PET imaging is the result of p-Ps and not o-Ps.…”

Section: Discussion: Positrons In Tissuementioning

confidence: 99%

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

Harpen¹

2003

Med. Phys.

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The PET-CT scanner, which overlays a high spatial resolution CT image on a relatively low resolution physiologic PET image, has greatly increased the efficacy of the PET imaging modality. With the resulting increase in the presence of PET imaging in the radiologic and medical physics communities, medical physicists can expect professional responsibilities in acceptance testing, quality assurance, radiation safety and resident teaching of this new modality. With this in mind we present a review of a subtle aspect of PET: the formation, symmetry properties and decay of positronium; the hydrogen like positron-electron complex which forms prior to annihilation.

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Section: Discussion: Positrons In Tissuementioning

confidence: 99%

Section: Discussion: Positrons In Tissuementioning

confidence: 99%

Section: Discussion: Positrons In Tissuementioning

confidence: 99%

Section: Discussion: Positrons In Tissuementioning

confidence: 99%

See 2 more Smart Citations

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

Harpen¹

2003

Med. Phys.

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“…The fraction of positrons forming positronium is known as the Ps yield. Using the technique of Positron Age-Momentum-Correlation (AMOC), Castellaz et al (2002) have measured Ps yields in a variety of liquids for an external 4 MeV positron beam. The Ps yield in water was found to be 38% and in other liquids (organic solvents) it can be as high as 70% in spite of positron recoil effects at the liquid surface.…”

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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Coincidence Doppler broadening study of polar and nonpolar molecules in liquid and solid states

Suzuki

Ito

et al. 2005

Chemical Physics Letters

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Positron Age-Momentum-Correlation (AMOC) Measurements on Organic Liquids

Cited by 13 publications

References 12 publications

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

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

Positron range estimations with PeneloPET

Coincidence Doppler broadening study of polar and nonpolar molecules in liquid and solid states

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