[Influence of count rate on image quality in three-dimensional PET acquisition].

ABSTRACT

OBJECTIVE: In FDG-PET examinations, optimization of the injected dose and duration of acquisition are important in determining the physical performance of PET or the PET/CT scanner. This study was intended to elucidate the influence of count rate on image quality. METHODS: Three PET/CT scanners (Biograph sensation 16, Discovery ST, and Aquiduo) were used in this study. Body and scatter phantoms (NEMA 2001) and a cylindrical phantom (for QC use) were also used. Data acquisition was performed repeatedly for about 6 h to achieve a fixed 15 million counts of true plus scatter. The count rate performance and image quality (signal-to-noise ratio and contrast) of each frame were analyzed after data acquisition. The relationship between the count rate and image quality was also analyzed. RESULTS: A positive correlation between the random fraction (ratio of random to prompt count rate) and signal-to-noise ratio was found in all PET/CT scanners, but with differing effects of the count rate's influence on image quality. Image contrast was not correlated with count rate. CONCLUSION: Acquisition parameters must be determined by considering each scanner's effect on how count rate influences image quality.