Paediatric Dose Optimization for Long Axial Field-ofView FDG PET/CT

Aim/Introduction: Paediatric patients are more radiationsensitive, therefore minimizing exposure during imaging is vital, while tailoring protocols to their varying sizes and ages is complex. The European Association of Nuclear Medicine (EANM) developed the paediatric dose card, a tool helping to determine safe and sufcient tracer activity levels. This dose card relies on data from large retrospective paediatric patient cohorts. Consequently failing to incorporate recent breakthroughs in whole-body and long axial feld-of-view (LAFOV) PET/CT imaging, which hold signifcant promise for reducing radiation exposure in children. This study evaluates the potential dose reduction capabilities of LAFOV-PET/CT for paediatric [18F]FDG imaging. <br/>Materials and Methods: Between October 2021 and April 2024, 39 paediatric patients underwent [18F]FDG LAFOV-PET/CT imaging, aged 0.2 to 17 years (mean 11 ± 5.3). Post-introduction of the LAFOV system, a systematic dose reduction was implemented, resulting in a wide range of doses (0.6 to 4 MBq/kg) and scan durations (mean 9.3 ± 2.1 minutes, range 3 to 15 minutes). To facilitate data comparison, a regression model was employed to derive an average count statistic for the study cohort, so-called reference image quality (RIQ), corresponding to a dose model of 1.87 MBq/kg (1.2 MBq ofset) for a 5-minute scan. Subsequent reconstructions were generated at 100%, 75%, 50%, 25%, and 12.5% of the RIQ. Quantitative assessment focused on measuring SUV mean, max and peak within predefned liver volumes, alongside subjective clinical image quality (IQ) evaluation using a Likert scale by fve nuclear medicine physicians. <br/><br/>Results: The RIQ served as an internal reference for further dose-image quality optimization and already represents a reduction of 67% and 49% in FDG dose compared to the EANM dose cards of 2016 and 2023, respectively. Qualitative clinical IQ analysis demonstrated the possibility of additional dose reductions by 51% (0.78 MBq/kg, 3.5 MBq ofset) and 64% (0.55 MBq/kg, 3.12 MBq ofset) if the IQ is reduced to 4 and 3.5 Likert score, respectively. Quantitative image analysis revealed no signifcant reduction in mean SUV with up to a 50% dose reduction. <br/>Conclusion: This study highlights that LAFOVPET/CT can signifcantly reduce paediatric doses by a total of 88% and 81%, compared to EANM dose cards from 2016 and 2023, respectively, without compromising acceptable image quality. The dose-reducing potential can be further maximized by leveraging the ultra-high sensitivity mode of LAFOV-PET/CT, technology that has recently become available and was not covered in this work