A Multiscale Adult Female Breast Computational Mesh Model for External Beam and Internal Radionuclide Circulating Lymphocyte Dose
Abstract
Purpose
To develop tetrahedral mesh-based tissue models at the macro and micro-scale of the International Commission on Radiological Protection (ICRP) adult female mesh-type reference computational phantom (MRCP) breast inclusive of tissue-specific vasculature models for use in Monte Carlo (MC) radiation transport simulations.
Methods
Within the ICRP reference adult female, breast tissue is designated as either glandular or adipose, of which, each includes a specific quantity of homogenized blood. The current ICRP MRCP lacks distinct glandular lobular and ductal structures, which have been incorporated into this model for refined dosimetry. At the micro-scale, blood is modeled from an experimentally derived microvascular network, forming an interconnected network for both adipose and glandular tissue. At the macro-scale, blood is explicitly modeled utilizing a modified C++ vessel generation algorithm, perfusing glandular lobes as well as the homogenized adipose distributed throughout the breast. The fractional contribution of micro-scale blood is subtracted from the total blood, modifying vessel generating algorithm target parameters to capture remaining macroscale blood. MC simulations were performed in Particle and Heavy Ion Transport Code System (PHITS) for both micro and macro-scale models to compute specific absorbed fractions (SAFs) for monoenergetic photons, electrons, and alpha particles.
Results
Multi-scale models of breast glandular tissue and vasculature were created for the adult female MRCPs, subsequent dosimetry analysis indicate the inclusion of refined anatomical structures influence the distribution and quantity of dose throughout the breast.
Conclusion
The creation of refined macroscopic and microscopic models of the adult female reference breast have enhanced the anatomical accuracy and radiation dosimetry of currently utilized phantoms. This methodology can be applied for a variety of macroscopic breast sizes and microscopic vascular densities. In addition to current structures, future macro-scale fibroglandular and structure-specific micro-scale models will further enhance dosimetry and expand applicability of these models to more body morphometries.