title: Model of the point spread function of monolithic scintillator PET detectors for perpendicular incidence.
abstract: OBJECTIVE
  Previously, we demonstrated the potential of positron emission tomography detectors consisting of monolithic scintillation crystals read out by arrays of solid-state light sensors. We reported detector spatial resolutions of 1.1-1.3 mm full width at half maximum (FWHM) with no degradation for angles of incidence up to 30 degrees, energy resolutions of approximately 11% FWHM, and timing resolutions of approximately 2 ns FWHM, using monolithic LYSO:Ce3+ crystals coupled to avalanche photodiode (APD) arrays. Here we develop, validate, and demonstrate a simple model of the detector point spread function (PSF) of such monolithic scintillator detectors.
  
  
  METHODS
  A PSF model was developed that essentially consists of two convolved components, one accounting for the spatial distribution of the energy deposited by annihilation photons within the crystal, and the other for the influences of statistical signal fluctuations and electronic noise. The model was validated through comparison with spatial resolution measurements on a detector consisting of an LYSO:Ce3+ crystal read out by two APD arrays.
  
  
  RESULTS
  The model is shown to describe the measured detector spatial response well at the noise levels found in the experiments. In addition, it is demonstrated how the model can be used to correct the measured spatial response for the influence of the finite diameter of the annihilation photon beam used in the experiments, thus obtaining an estimate of the intrinsic detector PSF.
  
  
  CONCLUSIONS
  Despite its simplicity, the proposed model is an accurate tool for analyzing the detector PSF of monolithic scintillator detectors and can be used to estimate the intrinsic detector PSF from the measured one.
authors.affiliation: Delft University of Technology, Mekelweg 15, 2629 JB Delft, The Netherlands.
authors.forename: Marnix C
authors.initials: MC
authors.lastname: Maas
authors.forename: D J
authors.initials: DJ
authors.lastname: van der Laan
authors.forename: Carel W E
authors.initials: CW
authors.lastname: van Eijk
authors.forename: Dennis R
authors.initials: DR
authors.lastname: Schaart
authors.forename: Freek J
authors.initials: FJ
authors.lastname: Beekman
authors.forename: Peter
authors.initials: P
authors.lastname: Bruyndonckx
authors.forename: Cedric
authors.initials: C
authors.lastname: Lemaître
mesh_terms: D000465:Algorithms; D016477:Artifacts; D002563:Cerium / Q000737:chemistry; D003198:Computer Simulation; D004867:Equipment Design / Q000379:methods; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D015233:Models, Statistical; D009010:Monte Carlo Method; D017785:Photons; D049268:Positron-Emission Tomography / Q000379:methods*; D015203:Reproducibility of Results; D012542:Scattering, Radiation; D012588:Scintillation Counting; D014159:Transducers
chemical_list: D002563:Cerium