Optimization of enhanced energy window on a whole-body DOI PET system

The use of depth of interaction (DOI) detectors is one effective technique to improve the spatial resolution of whole-body PET imaging. We have developed a whole-body PET system with DOI detectors that achieves less than 3 mm (FWHM) uniform spatial resolution, independent of the radial position in the transaxial field of view. On the other hand, improvements in sensitivity and noise equivalent count rate (NECR) were expected by implementing the DOI-dependent extended energy window (DEEW) method, employing a different energy window for each layer. Furthermore, the energy-based selective coincidence (ESC) method reduces multiple coincidences. In this study, we investigated sensitivity and NECR improvements using the DEEW method and the optimized enhanced energy window setting. The DOI detector consists of dual-layer GSO crystals, and the DOI detectors are arranged into a circular detector ring with a diameter of 664 mm. We evaluated the sensitivity and NECR performance based on the NEMA NU2-2001 standard. ESC and DEEW (1^st layer: 412-624 keV, 2^nd layer: 200-300 keV + 400-624 keV) resulted in better system performance than the conventional method.