An analytic, moment-based method to estimate orthopositronium lifetimes in positron annihilation lifetime...

The presence of tumor hypoxia is known to correlate with poor patient prognosis. Measurement of tissue oxygen concentration can be challenging, but recent advancements using positron annihilation lifetime spectroscopy (PALS) in three-dimensional positron emission tomography (PET) scans have shown promise for hypoxia detection. In this work, a novel method for estimating the orthopositronium lifetime in PALS is presented.

We have developed an analytical method based on moments of the PALS histogram to estimate the orthopositronium lifetime. The method was characterized with respect to estimation bias and variance, and the bias-minimizing moments were found for various orthopositronium lifetimes.

For sufficient statistical power, the method produces monotonic, stable estimates. For cases with a lower number of photon counts, the method was characterized, and solutions are presented to correct for bias and estimation variability. For most cases, the bias-minimizing moments were $n=10,11,12$ .

This novel method does not require curve-fitting and thus it is less computationally intensive than methods which fit the PALS histogram. This method will be extended to and continue to be improved for use in positronium lifetime imaging.