ALGORITHMS FOR CALCULATING DETECTOR EFFICIENCY NORMALIZATION COEFFICIENTS FOR TRUE COINCIDENCES IN 3D PET

Accurate normalization of lines of response in 3D PET is a prerequisit e for quantitative reconstruction. Most current methods are component based, calculating a series of geometric and intrinsic detector effici ency factors. We have reviewed the theory behind several existing algo rithms for calculating detector efficiency factors in 2D and 3D PET, a nd have extended them to create a range of new algorithms. Three of th e algorithms described are 'fully 3D' in that they make use of data fr om all detector rings for the calculation of the efficiencies of any o ne line of response. We have assessed the performance of the new and e xisting methods using simulated and real data, and have demonstrated t hat the fully 3D algorithms allow the rapid acquisition of crystal eff iciency normalization data using low-activity sources. Such methods en able the use of scatter-free scanning line sources or the use of very short acquisitions of cylindrical sources for routine normalization.