Proton dose deposition in heterogeneous media: A TOPAS Monte Carlo simulation study

Jie Li; Xiangli Cui; Lingling Liu; Bingbing Li; Zhenle Fei; Wei Han

doi:10.1016/j.apradiso.2025.111665

Proton dose deposition in heterogeneous media: A TOPAS Monte Carlo simulation study

Appl Radiat Isot. 2025 Mar:217:111665. doi: 10.1016/j.apradiso.2025.111665. Epub 2025 Jan 4.

Authors

Jie Li¹, Xiangli Cui², Lingling Liu¹, Bingbing Li³, Zhenle Fei⁴, Wei Han⁵

Affiliations

¹ University of Science and Technology of China, Hefei, Anhui, 230026, China; Institute of Health and Medical Technology, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, Anhui, 230031, China; Radiotherapy Center, Hefei Cancer Hospital, Chinese Academy of Sciences, Hefei, Anhui, 230031, China.
² Institute of Health and Medical Technology, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, Anhui, 230031, China; Radiotherapy Center, Hefei Cancer Hospital, Chinese Academy of Sciences, Hefei, Anhui, 230031, China. Electronic address: xlcui@cmpt.ac.cn.
³ Institute of Health and Medical Technology, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, Anhui, 230031, China; Radiotherapy Center, Hefei Cancer Hospital, Chinese Academy of Sciences, Hefei, Anhui, 230031, China.
⁴ Department of Oncology, The 901th Hospital of Joint Logistics Support Force of the Chinese People's Liberation Army, Hefei, Anhui, 230031, China.
⁵ Institute of Health and Medical Technology, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, Anhui, 230031, China. Electronic address: hanw@hfcas.ac.cn.

PMID: 39798271
DOI: 10.1016/j.apradiso.2025.111665

Abstract

This study investigated the influence of tissue electron density on proton beam dose distribution using TOPAS Monte Carlo simulation. Heterogeneous tissue models composed of 14 materials were constructed to simulate the dose deposition process of a 169.23 MeV proton beam. The study analyzed the relationships between electron density and key parameters such as maximum dose, total dose, and dose distribution. Results showed that increasing electron density led to higher local maximum dose, lower total dose, and decreased Bragg peak depth, range, penumbra width, and full width at half maximum (FWHM). High-density tissues caused a sharp, concentrated Bragg peak at shallower depths, while low-density tissues caused a backward shift and widening of the Bragg peak. Differences in proton energy deposition in various tissues were the fundamental reasons for dose distribution variations. This study quantified the relationship between electron density and proton beam dose distribution, providing a reference for accurate dose calculation and optimization in proton therapy.

Keywords: Dose distribution; Electron density; Heteogenerous media; Monte Carlo simulation; Proton therapy.