A STATIONARY SAMPLING SCHEME FOR MULTILAYER POSITRON TOMOGRAPHS

A stationary sampling scheme applicable to tomographic instruments inc orporating two or more detector layers is described and tested. In thi s concept, the detectors in adjacent layers are angularly offset by ha lf the interdetector distance. By reconstructing in one single slice a ll lines of response defined by two adjacent rings of detectors, a fou rfold increase in the number of coincidence lines is obtained and a un iform sampling distance equal to one-quarter the interdetector spacing is achieved. Whereas this is obtained at the expense of a 100 percent degradation of the resolution in the axial direction, with the recent breed of PET scanners using nearly square cross section detectors, th e resolution loss may be tolerable in many situations. In addition, no rmal reconstruction of the individual coincidence planes is always pos sible. The sampling concept was investigated experimentally with the h elp of the Universite de Sherbrooke PET camera simulator.