Abstract: The present invention provides terbium or lutetium garnet x ray scintillators activated with a rare earth metal ion, such as cerium, and treated by annealing in a controlled atmosphere comprising a predetermined amount of oxygen for a predetermined time and temperature to reduce radiation damage that would otherwise occur when the scintillator material is exposed to high energy radiation, such as the type of radiation required to use the scintillator for medical radiographic imaging and the like. In an embodiment, a single crystal or a polycrystalline scintillator comprising the general formula (Tb1−xLuxCey)3Al5O12 (where 0<×≦0.5, and y is in the range from about 0.0005 to about 0.2, and annealed at 1400° C. to 1500° C. in a controlled atmosphere comprising 1×10−6 to 0.22 atm oxygen shows an increased resistance to radiation damage.