The ECAT HRRT: NEMA NEC evaluation of the HRRT system, the new high-resolution research tomograph

The ECAT HRRT (high-resolution research tomograph) is a three-dimensional(3-D)-only dedicated brain positron emission tomograph (PET) with LSO and GSO scintillators. The system is based on eight panels of detectors. The HRRT´s imaging performance has previously been tested with phantoms and FDG scans performed in animal and human brains that showed significantly improved spatial resolution, below 2.5 mm for animal studies and below 3 mm for brain studies. The NEC count rate performance has been evaluated based on the NU 2-2001 protocol. The results show a peak NEC approximately 30% higher than the performance of the ECAT HR+, this in spite of a more shallow detector for the HRRT, only 15 mm relative to the 30 mm for the HR+. However, peak NEC as derived from the 70-cm line source phantom is not optimized for the performance of dedicated brain scanner. NEC data derived with a 20-cm diameter, 20-cm long phantoms show a peak NEC more than 60% higher than for the HR+. The reasons for the high performance are due to several factors, the large axial coverage, the short timing window of 6 ns, and the low detector dead time, all factors that imply the use of fast LSO and GSO scintillators.