PERFORMANCE EVALUATION OF THE PC-2048 - A NEW 15-SLICE ENCODED-CRYSTAL PET SCANNER FOR NEUROLOGICAL STUDIES

We report initial experience with the Scanditronix PC 2048-15B, a 15-slice PET system using multicrystal/multi-PMT modules to obtain high spatial resolution. Design parameters include: crystal dimensions = 6 x 12 x 30 mm; crystal: PMT encoding = 16:4; ring diameter = 50.5 cm; collimator length = 9 cm; slice separation = 6.5 mm; coincidence resolving time = 20 ns. Using an orbiting Ge-68 rod source for transmission scans, random and scattered events are reduced by only accepting coincidence lines which intersect the instantaneous position of the source. Scatter correction of the emission data is removed with a deconvolution kernel, random and dead-time correction by use of observed singles rates. System efficiency for the direct and cross slices are 9.7 and 13.7 Kcps/(mu-Ci/cc) from a 19 cm flood phantom. The peak count rates are 11.7/20.0 Kcps for the direct/cross slices at concentrations of 4.5/5.1-mu-Ci/cc, respectively. Taking scatter and randoms into account, the peak noise-effective count rates are 7.1/11.3 Kcps for direct/cross slices at 3.3/3.6-mu-Ci/cc, respectively. Random coincidences are 8-9% of the total rate at 0.8-mu-Ci/cc. Over the radial range 0-9 cm from the ring center, radial transverse resolution (FWHM is wobble mode) is 4.6-6.4 mm and tangential transverse resolution is 4.6-5.1 mm using a Hanning filter. Over the same range, axial resolution varies from 6.1-6.2 mm in direct slices and from 5.4-7.1 mm in cross slices. This near-isotropic resolution allows collection of image volume data with no preferred direction for signal averaging errors.