Investigation of a Model-based Time-over-threshold Technique for Phoswich Crystal Discrimination.

The best crystal identification (CI) algorithms proposed so far for phoswich detectors are based on adaptive filtering and pulse shape discrimination (PSD). However, these techniques require free running analog to digital converters, which is no longer possible with the ever increasing pixelization of new detectors. We propose to explore the dual-threshold time-over-threshold (ToT) technique, used to measure events energy and time of occurence, as a more robust solution for crystal identification with broad energy windows in phoswich detectors.

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

The Time-over-Threshold (ToT) analog-to-digital signal processing approach provides a power-efficient and cost-effective technique to extract all relevant information from detectors in high-energy physics and Positron Emission Tomography (PET) imaging. In this work, three calibration methods were investigated to correct the inherent nonlinear response of the ToT data using 1) -ray sources of various energies, 2) internal electronic gain variation in the LabPET II ASIC in combination with a single energy -ray source, and 3) internal gain variation along with an embedded pulse charge generator in replacement of a -ray source. The electronic gain calibration technique was shown to achieve equivalent correction accuracy as the -ray sources calibration.