A scintillator for positron emission tomography is provided. The scintillator includes a garnet compound of a formula of A3B2C3O12 and an activator ion consisting of cerium. A3 is A2X. X consists of at least one lanthanide element. A2 is selected from the group consisting of (i), (ii), (iii), and any combination thereof, wherein (i) consists of at least one lanthanide element, (ii) consists of at least one group I element selected from the group consisting of Na and K, and (iii) consists of at least one group II element selected from the group consisting of Ca, Sr, and Ba. B2 consists of Sn, Ti, Hf, Zr, and any combination thereof. C3 consists of Al, Ga, Li, and any combination thereof. The garnet compound is doped with the activator ion.