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The three-photon yield from e+ annihilation in various fluids.
K Mercurio1, P Zerkel, R Laforest
1Department of Physics, Washington University, St Louis, MO 63130, USA.
Physics in Medicine and Biology
|August 17, 2006
Summary
Triplet positronium decays into three photons, a process studied for medical imaging. This research found the three-photon yield in blood-like samples is 0.25%, with minimal oxygen dependence, suggesting imaging potential.
Area of Science:
- Atomic and Molecular Physics
- Medical Imaging Physics
- Radiochemistry
Background:
- Triplet positronium (Ps) decay emits three photons, a phenomenon explored for medical imaging applications.
- Previous studies noted enhanced three-photon yields in low oxygen environments, but data in biological liquids were lacking.
Purpose of the Study:
- To measure the delayed three-photon decay yield of positronium in biologically relevant liquids.
- To investigate the influence of dissolved oxygen levels on this yield.
- To assess the potential of three-photon emission for medical imaging.
Main Methods:
- Utilized coupled differential equations to fit the time dependence of two-photon yield data.
- Extracted the delayed three-photon decay yield at varying oxygen concentrations.
- Modeled positron capture, positronium formation, decay, and spin state interconversion.
Main Results:
- The delayed three-photon fraction was determined to be 0.25% in water and blood-like samples.
- This fraction showed negligible dependence on dissolved oxygen content.
- Assuming a standard direct annihilation component, the total three-photon fraction was calculated as 0.52%.
Conclusions:
- The three-photon decay yield in biological samples is low and largely independent of oxygen levels.
- These findings provide crucial data for evaluating positronium three-photon emission as a medical imaging modality.
- Further research may refine the application of this technique in biological contexts.