GAMMA RAY DETECTOR FOR POSITRON CT

摘要

PURPOSE:To obtain a gamma ray detector that suits to a positron CT of high resolving power and high S/N by so constituting the same that the outside shape of a crystal group and the shape of a photodetecting surface assume a square shape and coincide exactly and that the fluorescence from the crystals is transmitted efficiently to a PMT side. CONSTITUTION:A reflection film 3 is so constituted as to cover not only the crystal surfaces but also the PMT side surfaces downward sufficiently from the position level of a photoelectric surface. The light propagating in the outside wall direction at this time is perfectly scatttered and reflected by the BaSO4 coated on the outside wall and propagates again to the photoelectric surface side. If necessary, the reflection film on the outside wall is also formed between 1' and 1'' by a scepter such as lead tungstate so that the fluorescences of the crystals 1' and 1'' arrive effectively at the PMT side. It is also possible to form a refelection film like a wedge in the lower part of the crystal connecting surface by increasing the thickness of an optical coupling film 4 and to reflect the light in a diagonal direction in order to reduce the crosstalk of the light from both crystals.