Limitations of energy-based scatter correction for quantitative PET

Energy-based scatter correction (EBSC) was investigated using Monte Carlo simulation. In theory EBSC has possibilities that make it very appealing, including accounting for out-of-the-field-of-view (out-of-FOV) activity distributions without knowledge of those distributions. Out-of-FOV activity can account for a substantial portion of detected scatter in tomographs with septa retracted. Unfortunately, the majority of scattered events consist of photons which have energy too close to 511 keV to be distinguished from unscattered photons. In a head tomograph with no axial collimation, 60% of scattered events have scattered less than 30° (450 keV). For this reason EBSC is unlikely to be useful for quantitative positron emission tomography (PET) at typical energy resolutions (120 keV full width half maximum)