Recommended administered activities for 68Ga-labelled peptides in paediatric nuclear medicine

The aim of this study was to establish a method for determining administered activities for Ga-68-labelled peptides. Dose calculations were based on the weight-independent effective dose model proposed by the EANM paediatric dosage card for use in paediatric nuclear medicine. Previously published time-integrated activity coefficients for Ga-68-DOTATATE, Ga-68-DOTATOC and Ga-68-pentixafor were used to calculate age-independent effective doses. Consequently, the corresponding weight-dependent effective dose coefficients were rescaled according to the formalism of the EANM dosage card to determine the radiopharmaceutical class of Ga-68-labelled peptides (multiples) and to calculate the baseline activities based on an upper limit for administered activity (185 MBq) in an adult. All calculated normalization factors suggest that the Ga-68-labelled peptides are class B radiopharmaceuticals. The baseline activity for all compounds is 12.8 MBq. In analogy to F-18-fluoride, we recommend a minimum activity of 14 MBq. For paediatric nuclear medicine applications involving Ga-68-labelled peptides, we suggest determining administered activities based on the formalism proposed in this work. The corresponding effective doses from these procedures will remain age-independent.