EXPERIMENTAL STUDIES ON THE ANGULAR-DISTRIBUTION OF SCINTILLATION LIGHT FROM SMALL BGO CRYSTALS

The angular distribution of light emitted when a 511 keV gamma ray imp inges on a small 2 x 2 x 20 mm BGO scintillation crystal is calculated by Monte-Carlo simulation and experimentally verified via its intensi ty distribution on a CCD sensor at various distances. Direct compariso n of calculated and experimental images confirms that the angular dist ribution of the scintillation light is Lambertian with an index of dir ectivity between 0.8 and 1.0. The long-term goal of our project is the construction of a dual positron emission tomography (PET) - magnetic resonance imaging (MRI) scanner. Accurate knowledge of the angular dis tribution of light emitted from small crystals is crucial for the impl ementation of fibre-optic bundles that will efficiently transport the scintillation light out of the high magnetic field and constrained spa tial volume of the MRI magnet bore, to a convenient and low-held regio n meters away.