Means for measuring the depth interaction of gamma-rays in scintillation crystals in order to improve the spatial resolution of positron imaging systems

摘要

Arrays of scintillation crystals disposed on the circumference of a cylinder are used to detect the annihilation photons emitted after positron decay of isotopes within a body section. At the point of equi-probable depth of gamma ray interaction the surface treatment of each crystal is modified to absorb the light which otherwise would have been reflected by a small length of that surface. While light emitted from the rear of the crystal is nearly constant with depth, light emitted from the top front of the crystal is much reduced if the gamma ray interacts behind the absorbing band. When readout devices measure the light emitted from the top-front and rear face simultaneously it is possible to detect the region of interaction. This can be used to improve the spatial resolution of a positron imaging system.