Dual-Threshold Time-over-Threshold Nonlinearity Correction for PET Detectors.

Area of Science:

• Medical Imaging
• High-Energy Physics
• Signal Processing

Background:

• Time-over-Threshold (ToT) is a power-efficient analog-to-digital signal processing technique for detector data acquisition.
• ToT systems exhibit inherent nonlinear responses that require correction for accurate data extraction.
• Accurate calibration is crucial for applications like Positron Emission Tomography (PET) imaging.

Purpose of the Study:

• To investigate and compare three distinct calibration methods for correcting the nonlinear response of ToT data.
• To evaluate the feasibility of fast and accurate calibration for ToT data in PET imaging.
• To assess the impact of calibration methods on detector energy resolution.

Main Methods:

• Investigated three calibration approaches: 1) using various energy gamma-ray sources, 2) employing internal electronic gain variation with a single gamma-ray source, and 3) using internal gain variation with an embedded pulse charge generator.
• Compared the accuracy and efficiency of each calibration method.
• Assessed the energy resolution degradation of LabPET II detectors post-calibration.

Main Results:

• Electronic gain calibration achieved correction accuracy comparable to gamma-ray source calibration.
• The electronic gain variation method allows for faster calibration using a single gamma-ray source and automated gain sweeping.
• Energy resolution degradation was minimal (<12% and <8% for methods 1 and 2, respectively) compared to conventional ADC systems.

Conclusions:

• Fast and accurate calibration of ToT data nonlinearity is feasible for PET imaging.
• Electronic gain calibration presents a practical and efficient alternative for ToT data correction.
• The developed calibration techniques support the implementation of daily quality control for PET systems.