Time-based signal sampling using sawtooth-shaped threshold.

Area of Science:

• Nuclear Instrumentation
• Medical Imaging Physics

Background:

• Time-over-threshold (TOT) is a cost-effective method for energy measurement in silicon photomultiplier (SiPM) positron emission tomography (PET) systems.
• However, TOT suffers from poor energy resolution and linearity, limiting the performance of high-end PET detectors.
• Conventional analog-to-digital converter (ADC) approaches offer better performance but are more complex and power-hungry.

Purpose of the Study:

• To introduce a novel time-based signal-sampling method, sawtooth threshold sampling (STS), to overcome the limitations of TOT in PET scintillation detectors.
• To evaluate the performance of STS in terms of energy and timing resolution compared to TOT and high-speed ADC.

Main Methods:

• Developed an adaptive sawtooth-shaped threshold signal generator for scintillation pulse sampling.
• Estimated scintillation pulse amplitude by analyzing the time difference between rising and falling edges of the digital pulse train.
• Employed curve-fitting and numerical integration methods for energy estimation from STS samples.
• Conducted coincidence measurements using identical PET detector modules featuring SiPMs and LGSO crystals.

Main Results:

• The STS method achieved superior energy resolution (10.5% ± 0.21%) and timing resolution (200 ± 5.8 ps) compared to simple TOT (16.4% ± 0.52% and 224 ± 8.2 ps).
• STS performance was comparable to high-speed ADC (9.84% ± 0.11% and 193 ± 4.3 ps).
• The proposed STS circuit demonstrated its effectiveness in PET detector applications.

Conclusions:

• The novel sawtooth threshold sampling (STS) method significantly improves energy and timing resolution for PET scintillation detectors.
• STS offers a cost-effective alternative to conventional methods, enhancing PET system performance.
• This technique presents a promising solution for data acquisition in future SiPM-based PET systems.