Radiation dosimetry of [124I]-metaiodobenzylguanidine (mIBG) dynamic PET/CT in pediatric neuroblastoma through animal-to-human extrapolation with MCNPX code and OLINDA/EXM software

Iodine-124 metaiodobenzylguanidine (mIBG) positron emission tomography (PET)/computed tomography (CT) is well-established for imaging and pre-therapeutic dosimetry in pediatric neuroblastoma. However, direct dosimetry in children poses ethical and practical challenges. This study innovatively integrates animal-to-human extrapolation with Monte Carlo (MC) simulations using a pediatric model to estimate absorbed doses (ADs) of [ 124 I]-mIBG and benchmarks these results against clinical and computational methods. Human organ-specific time-integrated activity coefficients (TIACs) were derived from a prior animal study using a relative mass scaling factor. These TIACs were then utilized to calculate the final absorbed doses (ADs) in target organs, including the liver, kidneys, lungs, pancreas, stomach wall, spleen, urinary bladder wall, and brain. Results were validated in two steps: first by comparing MCNPX-derived ADs with OLINDA/EXM v1.1 outputs using relative percentage error (RPE), and then by benchmarking our animal-to-pediatric extrapolated data against an independent adult-to-pediatric extrapolation study. The MCNPX-derived ADs closely aligned with OLINDA/EXM results (RPE < 7 %) and with adult-to-pediatric extrapolation data (RPE < 6 %). The liver consistently absorbed the highest radiation dose, followed by the kidneys and lungs. This study underscores the feasibility and precision of using animal-to-human extrapolation in pediatric dosimetry, overcoming challenges of direct dosimetry within this population. By providing a reliable framework for [ 124 I]-mIBG dosimetry, it offers a path forward for personalized, safer treatment planning, enhancing the therapeutic efficacy of [ 131 I]-mIBG in pediatric neuroblastoma. • Developed a mice-to-human dosimetry framework for pediatric neuroblastoma. • Benchmarked MCNPX results against OLINDA/EXM and clinical data. • The liver received the highest absorbed dose, followed by the kidneys and lungs. • Achieved <7 % RPE between MCNPX and OLINDA/EXM results. • Enhanced pediatric dosimetry to optimize treatment planning and safety.