A Time-Walk Correction Method for PET Detectors Based on Leading Edge Discriminators

Area of Science:

• Nuclear Instrumentation and Detectors
• Medical Imaging Physics

Background:

• The leading-edge timing pick-off technique is a simple method for timing extraction in PET detectors.
• This technique suffers from inherent time-walk, degrading timing resolution, which is critical for time-of-flight (TOF) PET.
• Existing time-walk correction methods often rely on external reference detectors.

Purpose of the Study:

• To propose and evaluate a novel time-walk correction method for leading-edge timing discriminators in PET detectors.
• To improve the timing resolution of PET detectors without requiring external dedicated reference detectors.
• To assess the performance of the proposed method against conventional constant-fraction timing techniques.

Main Methods:

• A time-walk correction method was developed using timing information from two identical detectors, with one serving as a reference.
• Time-walk in the reference detector was minimized by selecting events within a narrow energy window (508.5–513.5 keV).
• A coincidence detector pair comprising SensL MicroFB SiPMs and LYSO crystals was assembled to validate the method.

Main Results:

• The proposed leading-edge based time-walk correction improved coincidence timing resolution from 389.0 ± 12.0 ps to 367.3 ± 0.5 ps (425–650 keV window).
• Further improvement was observed in a wider energy window (250–750 keV), with resolution changing from 670.2 ± 16.2 ps to 413.7 ± 0.9 ps.
• The achieved timing resolution was comparable to methods using a constant-fraction reference detector and superior to standard constant-fraction discriminators.

Conclusions:

• The proposed leading-edge based time-walk correction method effectively improves timing resolution in PET detectors.
• This technique offers an alternative to external reference detectors, simplifying system design.
• The method provides timing resolution performance equivalent to advanced techniques, demonstrating its practical viability.