Improving timing performance of double-ended readout in TOF-PET detectors

Area of Science:

• Medical Imaging
• Nuclear Physics
• Detector Technology

Background:

• Long scintillation crystals are crucial for high detection efficiency in clinical time-of-flight positron emission tomography (TOF-PET).
• However, crystal length degrades TOF-PET detector performance, specifically time and spatial resolution, due to photon travel time variations and parallax errors.

Purpose of the Study:

• To investigate double-ended readout TOF-PET detectors for improved coincidence time resolution (CTR).
• To analyze timing performance using various correction methods for depth-dependent effects in long crystals.

Main Methods:

• Studied double-ended readout TOF-PET detectors with long scintillation crystals coupled to SiPMs at both ends.
• Evaluated timing correction methods: individual photodetector trigger times, simple average, and weighted average based on inverse variances.
• Utilized a 3 mm × 3 mm × 25mm unpolished lutetium fine silicate (LFS) crystal with head-on irradiation.

Main Results:

• Achieved a CTR of 246 ps FWHM using depth-dependent timing correction and weighted average method.
• This represents a significant improvement over the 280 ps FWHM from the simple average method and 393 ps FWHM from single-ended readout.
• Demonstrated up to a 37% improvement in CTR compared to single-ended readout.

Conclusions:

• Depth-dependent timing correction with a weighted average is effective for double-ended readout TOF-PET detectors.
• This approach successfully corrects trigger time variations in long, unpolished crystals, enhancing CTR.
• The double-ended readout strategy offers a substantial performance gain for TOF-PET imaging.