What setting restricts the number of rings that can be used for coincidence detection?

The concept of ring plane difference relates to the geometry of the PET scanning system and plays a crucial role in defining how many rings are utilized for coincidence detection. Coincidence detection refers to the process of identifying simultaneous photon pairs emitted from a positron emission event, which are then detected by the ring(s) of detectors in a PET scanner.

The ring plane difference specifically pertains to the separation between the two detector rings used in PET imaging. This setting effectively shapes how the system detects coincidences. Limiting the number of rings provides several advantages, such as optimizing spatial resolution, managing costs, and reducing complexity in image reconstruction.

In contrast, while coincidence timing, detection efficiency, and energy resolution are important parameters in the overall function of a PET scanner, they do not directly dictate the number of rings employed for coincidence detection. Coincidence timing primarily addresses the temporal window within which detected photons are considered to be coincident. Detection efficiency refers to the ability of the system to accurately detect photons, and energy resolution reflects the system's capacity to differentiate between energies of detected photons. Thus, these factors influence the performance of the PET system but do not limit the structural capacity regarding the number of active rings for coincidence detection.