Comparison of different imaging geometries of brain SPECT systems

Since many different configurations of brain SPECT systems are available for clinical imaging, it is informative to investigate whether there are significant differences in their performance potentials. However, the difference in configurations and performance characteristics make direct comparison between systems difficult. To clarify the issue, we have developed a method to analyze the relative merits of different basic system geometries and configurations. This method is based on the calculated system geometric efficiency (SGE) which is obtained when the system spatial resolution is normalized to a reference level under a specified imaging condition. During the normalization process, the design parameters and performance of the collimators are iteratively adjusted to match the system resolution of an appropriately defined reference specification. After the collimator is normalized, the geometric efficiency (GE) of the collimator is calculated by summing the point source geometric efficiency (PSGE) over a brain source model while imposing narrow-beam attenuation effect. The SGE is then derived for each system configuration based on the calculated GE for each collimator. This analysis has been applied to many existing geometries and detector-collimator configurations of current brain SPECT systems