[en] Background: Harmonizing [¹⁸F]FDG brain PET/CT quantification aims to reduce variations across equipment, reconstruction algorithms, and protocols, ensuring consistent and reliable results. It is crucial for establishing PET as a robust biomarker for clinical decision-making and research since cross-population and center comparisons contribute to better understanding and treating neurodegenerative diseases. Harmonization strategies for quantitative PET have been validated clinically for various tumours. However, harmonizing PET/CT for neurodegenerative diseases still represents a challenge because some strategies require expensive phantoms and complex analysis. This study aims to evaluate whether a simple method using only a cylindrical phantom, originally developed for oncologic PET, can be applied to PET brain harmonization.