Author: Jared Baggett, Wesley E. Bolch, Lukas M. Carter, Robert Joseph Dawson, Laura Dinwiddie, Adam Leon Kesner, Cameron B. Kofler, Juan Camilo Ocampo Ramos, Yitian Wang, Stefan Wehmeier 👨🔬
Affiliation: University of Chicago, Department of Medical Physics, Memorial Sloan Kettering Cancer Center, University of Florida, MD Anderson 🌍
Purpose: To develop a slice-specific computed tomography (CT) organ dose library using Monte Carlo radiation transport simulations on a newly created set of newborn, infant, and toddler computational phantoms. The developed library forms the basis for fast calculations of total organ doses based on patient measurements and clinical protocols.
Methods: The library of mesh-type reference computational phantoms (MRCPs) used in generating organ doses was created using North American population survey data which includes standing height, weight, and head circumference. Phantoms are arranged by age from 0 to 2 years at 2-month increments, and height/weight groups of 10th, 50th, and 90th percentile. Monte Carlo simulations were conducted using a validated user-based CT source term in the Particle and Heavy Ion Transport code System (PHITS). These simulations were performed on a set of phantoms to generate slice-specific dosimetry datasets, incorporating various technique factors such as kVp, collimated beam width, and bowtie filter size. Total organ absorbed doses are then calculated for several common clinical CT studies by summing slice-specific doses over a scan range defined by anatomical landmarks, which are provided by an open-source CT protocol database.
Results: A database of slice-specific dose factors was generated for a library of newborn, infant, and toddler computational phantoms using several combinations of technique factors, which enable dose reconstructions for a range of clinical protocols.
Conclusion: Organ dose values have been generated and will be normalized using physical air kerma measurements. Dose values will be further adjusted based on pitch and the impact of tube current modulation (TCM). Summing slice-specific dose values over total scan length will provide accurate patient-dependent total organ dose estimates for a given scan protocol.