Pulse Pile-Up, Dead Time, Derandomization, and Count Rate Capability in Scintillation Gamma Cameras

A Monte Carlo calculation has been performed to simulate the count rate capability of a complete scintillation gamma camera system. The model includes an initial paralyzable dead time, pile-up rejection, a second paralyzable dead time, energy windowing, an N-bin derandomizer and a non-paralyzable dead time. This model has been successfully used to test the performance of existing cameras as well as to investigate the fundamental limitations of count rate performance. Parametric studies were made with each of the major system variables. Study of pile-up rejection demonstrates that the effective resolving time doubles by removing all pulses consisting of more than one event. Optimization of the derandomizer is analyzed. Factors limiting the current count rate capability and future potential are examined in terms of resolution and data loss.