Slat collimator design issues for dual head coincidence imaging systems

This work investigates optimum slat collimator design parameters for dual head coincidence imaging systems. Noise equivalent count rate was examined with respect to the activity concentration under various system conditions. All results are derived from Monte Carlo simulations with a digital anthropomorphic phantom. The DHCI system was modeled after the Millennium VG gamma camera (GEMS, Waukesha, Wisconsin). The dead-time characteristics of the camera were experimentally determined. The authors´ results suggests that substantial NEC gains can be achieved by varying the slat to slat separation, such that the peak of the NEC curve is located at clinically relevant levels (i.e., 0.07-0.10 μci/cc). The NEC was also found to increase by using longer slats with appropriately selected slat to slat separation. Furthermore, the NEC performance also depends on the count rate performance (i.e., deadtime losses) of the system. Therefore as improvements are made to the count rate capabilities of DHCI systems, the slat geometry should be modified. Further study is required to determine the effect slat collimator design has on image quality and lesion detection for clinically realistic imaging situations