Author: Wesley E. Bolch, Carlos G. Colon-Ortiz, Robert Joseph Dawson, Lazaro Fuentes Alfonso, Shreya P. Pathak, Julia D. Withrow 👨🔬
Affiliation: University of Florida 🌍
Purpose: To develop tetrahedral mesh-based tissue models within the breasts of the International Commission on Radiological Protection (ICRP) adult female mesh-type reference computational phantom (AFMRCP) at the macro-scale level and refine the existing homogenized breast model for use in Monte Carlo (MC) radiation transport simulations.
Methods:: Within the AFMRCP, the breast is divided into adipose and glandular tissue. Adipose tissue was modeled as a homogeneous volume, while glandular tissue was modeled as a collection of lobule units and lactiferous ducts to the nipple area. Respective internal thoracic vein-artery and lateral thoracic vein-artery entry vessels were manually modeled and directed into adipose tissue, at which point a blood vessel generation algorithm was initiated to perfuse each adipose region. Additional glandular unit perfusion was included to represent glandular blood volume. The number of vessels in the algorithmically generated tree was selected to achieve organ blood content of ICRP 145. MC simulations were performed in Particle and Heavy Ion Transport Code System (PHITS) to compute specific absorbed fractions (SAFs) for monoenergetic photons, electrons, positrons, and alpha particles on a 40% glandular fraction reference model.
Results: Macro-scale breast glandular tissue and vasculature models were created for the AFMRCPs, subsequent dosimetry analysis suggested that these highly detailed models are necessary for accurately assessing radiopharmaceutical therapy dose.
Conclusion: Anatomically accurate models of the breast at reference size and glandularity were constructed for the purpose of internal dosimetry. Up to 60% of glandular and adipose blood of ICRP Publication 145 was captured for lymphocyte tracking. This process can be repeated and applied to a family of breast sizes and glandularities for refined dosimetric measurements. In addition to breast sizes, this process is also applicable to a collection of changes in breast tissue marked by pregnancy. This work was supported by NCI Grant R01 CA248901 .