Advances in coincidence time resolution for PET.

Area of Science:

• Medical Imaging
• Materials Science
• Nuclear Physics

Background:

• Coincidence time resolution (CTR) is crucial for time-of-flight Positron Emission Tomography (TOF-PET) performance.
• LGSO:Ce (Lu1.8Gd0.2SiO5:Ce) crystals exhibit controllable decay times (30-40 ns) and promising properties for TOF-PET applications.
• Crystal element dimensions significantly impact timing performance due to scintillation photon transit time variance.

Purpose of the Study:

• To investigate the coincidence time resolution (CTR) achievable with LGSO:Ce (0.025 mol%) crystals coupled to novel silicon photomultipliers.
• To evaluate the effect of crystal element dimensions on timing performance in TOF-PET detectors.
• To present comprehensive measurements of light yield and intrinsic decay time for LGSO:Ce (0.025 mol%).

Main Methods:

• Fabrication of LGSO:Ce crystals with controlled cerium concentrations.
• Coupling LGSO:Ce crystals of varying dimensions (2.9 × 2.9 × 3 mm³ and 2.9 × 2.9 × 20 mm³) to silicon photomultipliers.
• Measurement of coincidence time resolution (CTR) using pairs of crystal elements.
• Characterization of light yield and intrinsic decay time.

Main Results:

• LGSO:Ce (0.025 mol%) crystals demonstrated controllable decay times.
• Shorter crystal elements (2.9 × 2.9 × 3 mm³) achieved a CTR of 80 ± 4 ps FWHM.
• Longer crystal elements (2.9 × 2.9 × 20 mm³) resulted in a CTR of 122 ± 4 ps FWHM.
• Light yield and intrinsic decay time measurements were performed.

Conclusions:

• LGSO:Ce crystals, particularly shorter elements, offer excellent potential for improving CTR in TOF-PET systems.
• Crystal element length is a critical factor influencing timing resolution, balancing detection efficiency and transit time variance.
• LGSO:Ce (0.025 mol%) shows significant promise as a scintillator for advanced TOF-PET imaging.