TY - JOUR
T1 - The three-photon yield from e+ annihilation in various fluids
AU - Mercurio, K.
AU - Zerkel, P.
AU - Laforest, R.
AU - Sobotka, L. G.
AU - Charity, R. J.
PY - 2006/9/7
Y1 - 2006/9/7
N2 - 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 O2 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 O2 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.
AB - 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 O2 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 O2 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.
UR - http://www.scopus.com/inward/record.url?scp=33747603254&partnerID=8YFLogxK
U2 - 10.1088/0031-9155/51/17/N05
DO - 10.1088/0031-9155/51/17/N05
M3 - Article
C2 - 16912371
AN - SCOPUS:33747603254
SN - 0031-9155
VL - 51
SP - N323-N329
JO - Physics in medicine and biology
JF - Physics in medicine and biology
IS - 17
M1 - N05
ER -