Author: Wesley E. Bolch, Chansoo Choi, Robert Joseph Dawson, Bangho Shin, Yitian Wang ðĻâðŽ
Affiliation: University of Florida ð
Purpose: The skeleton plays a critical role in dosimetry, containing red bone marrow (RBM) and bone endosteum (BE), which are closely linked to radiation-induced leukemia and bone cancer. While several groups, including ours, have developed adult skeletal models using micro-CT images, comparable models for pediatric populations remain unavailable despite their high radiation sensitivity. This study aims to develop the first image-based pediatric skeletal models in high-quality mesh format, advancing skeletal dosimetry accuracy for pediatric populations.
Methods: Given the impracticality of acquiring micro-CT images directly from pediatric populations, detailed pediatric skeletal models in mesh format were developed using our in-house C++ code through the following steps. Adult trabecular bone models from micro-CT images were adjusted to match age-specific trabecular parameters. A 50-Ξm-thick BE was then defined, and yellow bone marrow (YBM) and RBM were assigned based on age-specific marrow parameters. Finally, the models were tetrahedralized. Note that age-specific parameters were determined from a comprehensive review of scientific literature and ICRP publications.
Results: This study developed a comprehensive set of detailed pediatric skeletal models in mesh format. A total of 39 models were developed for the newborn, 1 year, 5 years, and 10 years, respectively. For 15 years, 35 models were created for the male and 39 for the female. The models define five skeletal tissue regions: trabecular bone, RBM and YBM in shallow marrow (within the BE), and RBM and YBM in deep marrow (outside the BE). All regional volumes were matched to target parameters with an accuracy of within 1%.
Conclusion: The pediatric skeletal models developed in this study are the first image-based models for pediatric populations, addressing limitations in pediatric skeletal dosimetry resulting from the use of adult-focused models. These models are expected to enhance skeletal dosimetry for pediatric populations across various radiation exposure scenarios, including radiopharmaceutical therapy.