Evaluation of image quality with four positron emitters and three preclinical PET/CT systems

Background We investigated the image quality of 11 C, 68 Ga, 18 F and 89 Zr, which have different positron fractions, physical half-lifes and positron ranges. Three small animal positron emission tomography/computed tomography (PET/CT) systems were used in the evaluation, including the Siemens Inveon, RAYCAN X5 and Molecubes β-cube. The evaluation was performed on a single scanner level using the national electrical manufacturers association (NEMA) image quality phantom and analysis protocol. Acquisitions were performed with the standard NEMA protocol for 18 F and using a radionuclide-specific acquisition time for 11 C, 68 Ga and 89 Zr. Images were assessed using percent recovery coefficient (%RC), percentage standard deviation (%STD), image uniformity (%SD), spill-over ratio (SOR) and evaluation of image quantification. Results 68 Ga had the lowest %RC ( 85%) and lowest %STD for the 5 mm rod across all systems. For 11 C and 89 Zr, the maximum %RC was close (> 76%) to the %RC with 18 F. A larger SOR were measured in water with 11 C and 68 Ga compared to 18 F on all systems. SOR in air reflected image reconstruction and data correction performance. Large variation in image quantification was observed, with maximal errors of 22.73% ( 89 Zr, Inveon), 17.54% ( 89 Zr, RAYCAN) and − 14.87% ( 68 Ga, Molecubes). Conclusions The systems performed most optimal in terms of NEMA image quality parameters when using 18 F, where 11 C and 89 Zr performed slightly worse than 18 F. The performance was least optimal when using 68 Ga, due to large positron range. The large quantification differences prompt optimization not only by terms of image quality but also quantification. Further investigation should be performed to find an appropriate calibration and harmonization protocol and the evaluation should be conducted on a multi-scanner and multi-center level.