Allegro的calibration

Imaging Characteristics of a 3-Dimensional GSO Whole-Body PET Camera
Suleman Surti, PhD; and Joel S. Karp, PhD
THE JOURNAL OF NUCLEAR MEDICINE • Vol. 45 • No. 6 • June 2004

For an accurate measurement of interaction position in the detector and the deposited energy, a PMT gain matching needs to be performed to compensate for the PMT gain differences. Additionally, the collected light has a maximum of 20% difference between events at a PMT center and its edges. This is due to loss of collected light in the gaps between the hexagonally packed PMTs and small variations between light outputs of indi- vidual crystals. To achieve good system energy resolution, a position-based energy correction (scaling) is performed through a lookup table. The final data correction before sinogram binning involves identification of crystal boundaries. This must take into consideration the spatial nonlinearity of the calculated position, which is a characteristic of all Anger-logic detectors. An automated search algorithm previously developed for the G-PET (1) brain scanner has been adapted for Allegro. This algorithm detects the minima (between crystals) within a high-count flood histogram, defines the crystal boundaries around each crystal, and assigns a real position to all events that occur within each bound- ary region.

After all of these corrections have been performed, the acquired data from the scanner are binned into a sinogram with 161 angles
and 295 rays for every ring combination (total of 29^2=