Radiation detector developments in medical applications: Inorganic scintillators in positron emission tomography

In recent years, a number of new gamma-ray scintillators are commercially available. These scintillators are either derived from known scintillators, e. g. Lu(1-x)Y(x)AlO(3): Ce (LuYAP) from LuAlO(3): Ce and Lu(2(1-x))Y(2x)SiO(5): Ce (LYSO) from Lu(2)SiO(5): Ce or are the result of new discoveries, e. g. LaCl(3): Ce and LaBr(3): Ce. The first two materials are primarily of interest because of the relatively high detection efficiency and fast response; LYSO has found application in time-of-light (TOF) positron-emission tomography ( TOF PET) and the LuYAP-LYSO combination is used in small-animal PET. The halide scintillators have an excellent energy resolution of similar to 3% at 662 keV and they have a relatively high light yield. LaBr3: Ce is being studied for application in TOF PET. At the same time, the search for and research on new scintillator materials are going on. For example, LuI(3): Ce is a new material with a very high light yield (similar to 90 000 photons MeV(-1)). Other examples of new materials are (C(6)H(13)NH(3))(2)PbI(4) and (C(3)H(7)NH(3))(2)PbBr(4), organic-inorganic hybrid compounds, of which the former has a very fast sub-nanosecond response. The new scintillators show great promise for new developments in medical applications, in particular, for PET systems.