Author: Peter Balogh, Wesley E. Bolch, Mir Md Nasim Hossain, Nien-Wen Hu, Walter Murfee, Wyatt Smither, Julia D. Withrow 👨🔬
Affiliation: New Jersey Institute of Technology, University of Florida 🌍
Purpose: To develop 3D computational, tissue-representative models incorporating physiologically relevant microvascular network patterns for calculating local alpha particle and electron dosimetry effects. It is hypothesized that to compute scale-accurate doses for shorter range alpha particles and lower energy electrons, explicitly modeled blood and lymphatic microvasculature must be considered in radiation transport simulations.
Methods: To obtain relevant microvascular network patterns, adult rat mesenteric tissues labeled for PECAM (blood vessel marker) and Lyve-1 (lymphatic marker) were imaged. Representative images of network regions were then imported into the Creo Parametric software and converted to a 3D surface polygon mesh model that incorporated vessel diameters, lengths and patterns. Post conversion of the structures into a tetrahedral mesh with delineated material properties was performed using POLY2TET. The model was then incorporated into the Particle and Heavy Ion Transport code System (PHITS), a Monte Carlo-based radiation transport code, and absorbed fractions were computed for the blood microvascular, lymphatic and interstitial regions. Simulations were performed for alpha particles of energies 1-12 MeV in increments of 0.5 MeV and for electrons on a logarithmic energy grid from 10 keV to 10 MeV, consisting of 25 energies.
Results: The applicability of our model framework was supported by the computation of absorbed fractions for alpha particles and electrons. In the low energy simulations, absorbed fractions in non-source target regions were approximately zero due to minimal escape from the source regions. Absorbed fractions approached the volume fraction of the target region with increasing energy source particle.
Conclusion: Three microscale models inclusive of blood and lymphatic vasculature were developed with spatial variation in vasculature patterning. A data set of absorbed fractions for alpha particles and electrons in each of the regions in the model acting as sources and targets was generated.