**Abstract**

Nowadays, the value of paediatric nuclear diagnostic medical imaging has been well established within the medical community. Despite decades of nuclear medicine practice, studies in nuclear medicine to achieve the lowest possible radiation dose to the patient while ensuring the optimized image quality have to be continued. Numerous studies highlighted a long list of objectives, in order to obtain the minimum possible absorbed dose, achieve short scan times and generate images with a high signal to noise ratio (SNR) and spatial/temporal resolution. For the development of guidelines, it is necessary to study the handling of radiopharmaceuticals, the dose splitting processes, the quality control protocols, the plan design of infrastructures, the availability of optimized dose calibrators for the corresponding radiopharmaceuticals, the development of new more sensitive radiopharmaceuticals, and optimized protocols for diagnostic or therapeutical examination of the patient. Anthropomorphic phantoms are used to model paediatric patients, but anatomical models and their pharmacokinetic data are not applied directly to any specific patient. There is a need for the development of personalized dosimetry in children. Factors regarding age, weight and biological and molecular background of the pathology must be included in paediatric personalized dosimetry. The developmental process of the child, as shape, mass, volume, anatomy, physiological indices (metabolism, heart rate, etc.) and variations due to pathologies should be taken under consideration. Corrections of radiation time of the target organ, in relation to neighbouring tissues, blood supply, estimation of residual activity/time and clearance rate are parameters in the calculations of paediatric dosimetry in nuclear medicine. In hybrid imaging examinations with computed tomography modality, the contribution of absorbed dose from CT to the paediatric patient must also be calculated.

**Keywords:** paediatric dose phantoms, PDRL, effective dose, image gently, paediatric radiosensitivity, individualize dosimetry
