ABSTRACT
PET scanners use multiple rings of detectors that surround the patient to record coincidence photon pairs produced by positron annihilation. Early PET scanners placed septa between rings to collect coincidence events only within each detector ring. This is commonly referred to as 2D PET since the data consist of a stack of 2D sinograms and can be reconstructed using a 4302D filtered back projection algorithm slice by slice. * With the developments of fast scintillators and electronics, modern PET scanners no longer require septa and can accept all coincidence events. This results in a factor of 4–7 increase in sensitivity and hence increases the signal-to-noise ratio (SNR). PET without septa is commonly referred to as fully 3D PET. The higher sensitivity of fully 3D PET can be used to reduce injection dose or scan time or to improve image quality. The data, however, are overcomplete and require new reconstruction algorithms.
