Determining scintillation pulse shapes of fast PET scintillators

Abstract

Determining the scintillation pulse shapes of PET scintillation crystals, especially the rise time of the pulse, will yield valuable information for making choices in the design of time of flight-PET scanners, with respect to e.g. scintillator crystal material and the detector trigger schemes. This can eventually improve the image quality of PET scans by noise reduction and/or reduce the image acquisition time and the dose to the patient. Knowledge of the rise time of the scintillation pulse is also of great importance in the modelling of the physical processes involved in scintillations. Several setups are presented and assessed with the intention to develop a procedure that is relatively easy to implement and is suitable for determining scintillation pulse shapes of PET scintillation crystals, excited by 511 keV photons, with sub-nanosecond timing resolution. The emphasis is on characterizing the rising edge of the scintillation pulse. The time correlated single photon counting method was employed in all of the setup variations. A proof-of-principle of the applicability of a suitable measurement procedure is given, which achieves a timing resolution of 120 ps FWHM and was used to determine the exponential rise time of a lutetium-yttrium oxyorthosilicate (LYSO) scintillator to be 81 ps with an estimated uncertainty interval of [50,120] ps. Also recommendations for further work on the basis of this procedure are made.