Cerium doped silicate yttrium, YSO(Ce), belongs to monoclinic rare earth ortho-silicate crystal, it is similar with the LYSO(Ce) crystal, while generally used as a semiconductor and in photo optic applications. YSO(Ce) crystal shares the same emission peak 420 nm with LYSO(Ce), but it is less efficient in terms of light output, which is around 18,000 Photons/MeV, the decay time of YSO(Ce) 50-70 ns is slower than LYSO(Ce)`s 40 ns.