Multiple-hit parameter estimation in monolithic detectors.

Area of Science:

• Nuclear physics
• Medical imaging instrumentation
• Detector physics

Background:

• Accurate localization of gamma ray interactions is crucial for medical imaging and physics research.
• Conventional methods often assume single interaction sites, limiting precision with multiple-hit events.
• Monolithic detectors offer advantages but require sophisticated methods for interaction reconstruction.

Purpose of the Study:

• To evaluate a maximum-a-priori (MAP) based multiple-hit estimator for gamma ray interaction position in monolithic detectors.
• To compare the performance of multiple-hit estimators against conventional single-hit estimators.
• To assess the impact of detector configuration and event filtering on estimator accuracy.

Main Methods:

• Utilized SCOUT, a Monte Carlo tool, for simulating gamma ray interactions in LSO block detectors.
• Employed a maximum-a-priori (MAP) method for estimating primary interaction positions with multiple hits.
• Compared bias and variance metrics between multiple-hit and conventional maximum likelihood (ML) single-hit estimators.
• Investigated the effect of likelihood-based event filtering on estimator performance.

Main Results:

• Observed a 1-12% improvement in intrinsic resolution using 1-or-2-hit estimators versus 1-hit estimators, depending on detector design.
• Demonstrated enhanced differentiation of photopeak events with multiple-hit estimators.
• Recovered over 6% of photopeak events rejected by 1-hit estimator filtering, with accurate positioning and no resolution loss.

Conclusions:

• The MAP-based multiple-hit estimation method offers significant improvements in gamma ray interaction localization for monolithic detectors.
• This advanced method enhances both the precision of interaction positioning and the accurate identification of relevant events.
• The findings suggest potential for improved performance in scintillation cameras and other gamma-ray detection systems.