Triple-head coincidence imaging with gamma camera PET system: spatial resolution, sensitivity and count rate performance

Positron emission tomography (PET) is currently performed using either dedicated PET scanner or gamma camera equipped with electronic circuitry for coincidence detection of 511 keV annihilation quanta (gamma camera PET system). While resolution limits of these two instruments are comparable, sensitivity and count rate performance of the gamma camera PET system is several times lower than that of the PET scanner. Most gamma camera PET systems are manufactured as dual-detector systems capable of performing dual-head coincidence imaging. This work investigates performance characteristics of triple-head gamma camera PET system and compares them with 2-head system. Following performance characteristics of the system were assessed: spatial resolution, sensitivity, count rate performance. Spatial resolution, expressed as full-width-at-half-maximum (FWHM), at 1 cm radius is 5.9 mm ; at 10 cm radius transverse radial resolution is 5.3 mm while transverse tangential and axial resolution are 8.9 mm and 13.3 mm respectively. Sensitivity for standard cylindrical phantom is 255 c×s-1×MBq-1, cşcounts, using 30%-width photopeak energy window. Increase of 35 % in the PET sensitivity is achievable by opening an additional 30%-width energy window in the Compton region. Count rate in coincidence mode, at the upper limit of system&#8217 ; s optimal performance, is 45 kc×s-1 using only photopeak energy window, and increases to 60 kc×s-1 when using photopeak + Compton windows. Resolution when imaging cold phantom objects (rods and spheres) is 10 mm. In conclusion, our triple-head gamma camera PET system has system sensitivity two times higher in comparison with a similar dual-head system. Spatial resolution is in the same range as in the most dual-head systems.