European ENVISION Project for Improving Timing Resolution in PET Systems
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Hadrontherapy uses charged particles to destroy tumors. For improving the quality assurance tools, specially range verification, the European Commission funded the project ENVISION. This paper summarizes the activities carried out within the work package two devoted to improve the visualization of the spatial distribution of positron emitters that are produced during patient irradiation. Allowing the beam passage implies a reduction in the angular coverage which degrades the range assessment. The aim of the work package two was to investigate the potential use of time-of-flight information for compensating this degradation. The studies can be classified into hardware and software developments. For the former, several ASICs and DAQs have been investigated. Also, the potential application of resistive plate chambers has been assessed. Four dual-head demonstrators have been produced by the end of the project. The software developments are divided into simulations and image reconstruction. Several algorithms able to include the time-of-flight information have been developed. Direct reconstruction has been implemented and compared with conventional maximum-likelihood methods. The results show that direct time-of-flight for on-line reconstruction is possible although iterative algorithms can achieve further improvements. However, time-of-flight alone might not be sufficient due to the low emission rates.
-  http://envision.web.cern.ch/ENVISION/
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