Inorganic scintillator, and radiation detector and PET apparatus employing it

xyzu The inorganic scintillator of the invention has the chemical composition represented by CeLnSiO(where Ln represents at least two elements selected from among Y, Gd and Lu. 0.001≦x≦0.1, 1.9≦y≦2.1, 0.9≦z≦1.1, 4.9≦u≦5.1) and emits fluorescence upon incidence of radiation, wherein the maximum peak wavelength in the intensity spectrum of the emitted fluorescence is a peak in the range between 450 nm and 600 nm.