The scintillation properties of LaBr3 doped with 0.5% Ce3+ are presented. Under optical and gamma ray excitation, Ce3+ emission is observed to peak at 356 and 387 nm. The scintillation light output is 61 000±5000 photons/MeV at 662 keV. More than 90% is emitted with a decay time of 35 ns. An energy resolution (full width at half maximum over the peak position) of 2.85%±0.05% was observed for the 662 keV full absorption peak. A time resolution of 385 ps was obtained using BaF2 as second scintillator and gamma rays of Co60.

Abstract-A review and new data are presented on the absolute photon yield emitted by "classical" (NaI(Tl+), CsI(Tl+), CsI(Na+), CaF2(Eu2+);+BigGe30n, and CdW04) and "modern" (BaF2, GdzSiOs(Ce ), Y A l o~( c e~+ ) , Lu2Si05(Ce3+), Lu3 A15 0 1 2 (Sc3+), and K2LaCl5 (Ce3+)) scintillation crystals after absorption of X-rays and y-rays of energies ranging from 5 keV to 1 MeV. Factors influencing the energy resolution with which high energy photons can be detected with scintillatorphotomultiplier combinations are reviewed. Attention is especially focused on the effects of nonproportionality in the scintillation response on the energy resolution.

A review of medical diagnostic imaging methods utilizing x-rays or gamma rays and the application and development of inorganic scintillators is presented.

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We developed positron emission tomography (PET) detectors based on monolithic scintillation crystals and position-sensitive light sensors. Intrinsic depth-of-interaction (DOI) correction is achieved by deriving the entry points of annihilation photons on the front surface of the crystal from the light sensor signals. Here we characterize the next generation of these detectors, consisting of a 20 mm thick rectangular or trapezoidal LYSO:Ce crystal read out on the front and the back (double-sided readout, DSR) by Hamamatsu S8550SPL avalanche photodiode (APD) arrays optimized for DSR. The full width at half maximum (FWHM) of the detector point-spread function (PSF) obtained with a rectangular crystal at normal incidence equals ∼1.05 mm at the detector centre, after correction for the ∼0.9 mm diameter test beam of annihilation photons. Resolution losses of several tenths of a mm occur near the crystal edges. Furthermore, trapezoidal crystals perform almost equally well as rectangular ones, while improving system sensitivity. Due to the highly accurate DOI correction of all detectors, the spatial resolution remains essentially constant for angles of incidence of up to at least 30• . Energy resolutions of ∼11% FWHM are measured, with a fraction of events of up to 75% in the full-energy peak. The coincidence timing resolution is estimated to be 2.8 ns FWHM. The good spatial, energy and timing resolutions, together with the excellent DOI correction and high detection efficiency of our detectors, are expected to facilitate high and uniform PET system resolution.