Investigating the temporal resolution limits of scintillation detection from pixellated elements: comparison between experiment and simulation

Abstract

This study investigates the physical limitations involved in the extraction of accurate timing information from pixellated scintillation detectors for positron emission tomography (PET). Accurate physical modeling of the scintillation detection process, from scintillation light generation through detection, is devised and performed for varying detector attributes, such as the crystal element length, light yield, decay time and surface treatment. The dependence of light output and time resolution on these attributes, as well as on the photon interaction depth (DoI) of the annihilation quanta within the crystal volume, is studied and compared with experimental results. A theoretical background which highlights the importance of different time blurring factors for instantaneous ('ideal') and exponential ('realistic') scintillation decay is developed and compared with simulated data. For the case of a realistic scintillator, our experimental and simulation findings suggest that dependence of detector performance on DoI is more evident for crystal elements with rough ('as cut') compared to polished surfaces (maximum observed difference of 64% (25%) and 22% (19%) in simulation (measurement) for light output and time resolution, respectively). Furthermore we observe distinct trends of the detector performance dependence on detector element length and surface treatment. For short crystals (3 × 3 × 5 mm(3)) an improvement in light output and time resolution for 'as cut' compared to polished crystals is observed (3% (7%) and 9% (9%) for simulation (measurement), respectively). The trend is reversed for longer crystals (3 × 3 × 20 mm(3)) and an improvement in light output and time uncertainty for polished compared to 'as cut' crystals is observed (36% (6%) and 40% (20%) for simulation (measurement), respectively). The results of this study are used to guide the design of PET detectors with combined time of flight (ToF) and DoI features.

Time resolution of the plastic scintillator strips with matrix photomultiplier readout for J-PET tomograph

“…in refs. ,2012b), Spanoudaki Levin 2011, Fishburn et al 2010 and the comprehensive account on this topic may be examined e.g. in ref.…”

Estudio e implementación de algoritmos digitales para la mejora de la resolución temporal en sistemas de tomografía por emisión de positrones

“…Los cambios en la resolución temporal debidos al efecto del centellador han sido estudiados en distintos trabajos [84,88,89,90,91,92,81], debido a que, si se considera un sistema ideal donde el PMT y la electrónica no introducen ningún error, la estadística del centelleo limita la resolución temporal alcanzable.…”

“…En los nuevos modelos estadísticos, tiende a introducirse el tiempo de subida τ subida [88,93], pues esta incertidumbre comienza a ser importante en TOF PET. Shao et al, en [93], proponen el siguiente modelo para f (t):…”

“…4.16, en el termino σ tP ROP . Estos factores han sido estudiados en diversos trabajos [84,91,90,89,88].…”

“…Observando los parámetros que afectan a la resolución temporal dentro del cristal, se puede decir que las características ideales del cristal para tiempos son [88,92]: Una elevada tasa de fotones generados por energía incidente. Este factor afecta a σ tEST A .…”