PET/CT acquisition and processing protocols in the Netherlands

To evaluate variations in acquisition and processing protocols for four of the most common PET/CT examinations in Dutch hospitals: FDG-WB, [¹⁸F]F-PSMA, [⁶⁸Ga]Ga-PSMA, and FDG-Brain.

All nuclear medicine departments in the Netherlands with a PET/CT scanner were invited to participate in a survey about acquisition and processing protocols for FDG-WB, [¹⁸F]F-PSMA, [⁶⁸Ga]Ga-PSMA, and FDG-Brain PET/CT examinations. The survey collected data on injected activity, acquisition times, and reconstruction/post-processing settings. From these data, we analyzed the weight-dependent injected activity, acquisition count statistics, and correlations with scanner performance (NEMA sensitivity).

A total of 42 hospitals responded (including all Dutch University Medical Centers), providing data from 58 PET/CT systems spanning 11 different models from 4 vendors. Injected activity and scan duration varied widely across hospitals, even for the same scanner model and examination type. A moderate negative correlation was observed between scanner sensitivity and the normalized injected activity × scan duration product for FDG-WB (R² = 0.50, slope = - 186.5) and FDG-brain (R² = 0.33, slope = - 180.8), suggesting that hospitals using higher-sensitivity scanners tend to reduce either injected activity or scan duration to maintain comparable acquisition counts. For [¹⁸F]F-PSMA (R² = 0.24, slope = - 62.6), the trend was less pronounced, indicating greater variability in how PET/CT centers adjust injected activity and scan duration for these tracers. In contrast, for [⁶⁸ Ga]Ga-PSMA (R² = 0.04, slope = - 28.3), no significant correlation was found, suggesting that scanner sensitivity plays a minimal role in protocol selection for these examinations. The observed variations in injected activity led to differences in patient radiation dose by a factor of 4 for FDG-WB, more than a factor of 10 for PSMA, and a factor of 5 for FDG-brain scans. These differences persist even after accounting for scan duration, scanner sensitivity, and overlap between scanning positions, highlighting substantial inconsistencies in PET/CT imaging protocols across Dutch hospitals.

The main objective of this survey was to determine the current state of practice in the Netherlands for three common PET/CT examinations. We observed variations in the injected activity for all PET/CT exam types, even within the same scanner model, that cannot be explained by taking into account differences in scanning times or uptake times. The direct implication of the observed variation in injected activity is a similar variation in radiation dose to the patient. We observed differences in dose to the patient of up to a factor 4 for FDG-WB, more than a factor of 5for [¹⁸F]F-PSMA, a factor of 4 for [⁶⁸ Ga]Ga-PSMA, and up to a factor of 5 for FDG-brain scans. Variations in count statistics, reconstruction, and processing settings for similar-weight patients on comparable PET/CT systems should be further investigated for their impact on lesion detectability.