LSO PET/SPECT spatial resolution: critical on-line DOI rebinning methods and results (original) (raw)

This aiticlc reports on PET-mode transaxial spatial rcsolution for a new hybrid PET/SPECT system. This systciii is based on a rotating dual-head tomograph using LSO/Nal scintillators and is capable of depth-of-interaction (DOI) measurement. For this LSO PET/SPECT, each detector head contains two 84x 120 planar arrays of crystalsone array NaI, the other LSO. LSO and Nal crystals are each 0 . 4 4~0 . 4 4~1 cm. In PET mode, each head is radially offset 36 cm from FOV center. Relative orientation of the two heads is 158 degrees. Dual-level DO[ discriminates LSO versus Nal by scintillation pulse decay time. While significant for good image resolution, dual-level DO1 isolates gamma detection only to the ( 1 cni) long axis depth of each individual crystal. Critical to delivery of excellent spatial resolution are additional methods to precisely characterize the depth of the centroid of the probability of gamma interaction along the crystal long axis. This depth is measured to +/-0.01 cm for each of 4 planar arrays and applied for more accurate LOR positioning in super-fast real-time rebinning hardware. With DO1 and measured centroid depth applied, FWHM transaxial spatial resolution is 0.4 cm at FOV center and 0.6 cm at I O cni off center. Without DOI, resolution degrades as much as 33%.