Technical note: A PBS source model based independent dose calculation frame on TOPAS MC

IF 2.7 3区医学 Q1 RADIOLOGY, NUCLEAR MEDICINE & MEDICAL IMAGING

Physica Medica-European Journal of Medical Physics Pub Date : 2025-08-14 DOI:10.1016/j.ejmp.2025.105074

Xuying Shang , Yaoying Liu , Xiaoyun Le , Zishen Wang , Xiaoqing Sun , Chunfeng Fang , Baolin Qu , Yue Zou , Wei Zhao , Gaolong Zhang , Shouping Xu

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引用次数: 0

Abstract

Purpose

We endeavor to present a comprehensive methodology for establishing a versatile Monte Carlo (MC) dose calculation platform that operates independently of the treatment planning system (TPS, e.g., RayStation).

Methods

We assumed the source emission plane was at the nozzle exit. To align with the measured data, we optimized the phase space parameters (spot size, angular spread, correlation, energy spread, and nominal energy) and the beam source model’s absolute dose (the number of protons per MU) in the source emission plane. Additionally, we devised a method that automatically converts patient plans into executable MC scripts capable of running in the TOPAS MC software.

Results

Our efforts successfully established a library encompassing the source model parameters. The disparities between the measured and simulated beam spot sizes were all below 0.3 mm. Moreover, the differences in the depth-dose curve’s distal falloff (R₉₀) were less than 0.1 mm, and the mean point-to-point dose differences were less than 0.7 %. Remarkably, the 3D gamma passing rates (GPRs) for three spread-out Bragg peaks (SOBPs, 3 mm/3% criteria) were 100 %. Furthermore, when comparing TOPAS and TPS MCs for 23 pencil beam scanning (PBS) patient plans, the mean 3D GPRs for 2 mm/2% and 3 mm/3% criteria were 99.96 % and 100 %, respectively.

Conclusion

We have successfully developed a comprehensive MC framework for PBS, employing a well-defined beam source model. The method we presented for building the PBS MC framework holds potential to build a dose verification tool and for scientific research.

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技术说明：基于TOPAS MC的独立剂量计算框架的PBS源模型

目的：我们努力提出一种全面的方法，用于建立一个独立于治疗计划系统（TPS，例如RayStation）运行的多功能蒙特卡罗（MC）剂量计算平台。方法假设源发射平面在喷管出口。为了与实测数据保持一致，我们优化了相空间参数（光斑大小、角扩展、相关、能量扩展和标称能量）和源发射平面上束流源模型的绝对剂量（每MU的质子数）。此外，我们设计了一种方法，将患者计划自动转换为可执行的MC脚本，能够在TOPAS MC软件中运行。结果我们成功地建立了一个包含源模型参数的库。实测光斑尺寸与模拟光斑尺寸的差异均在0.3 mm以下。此外，深度剂量曲线远端衰减（R90）差异小于0.1 mm，平均点对点剂量差异小于0.7%。值得注意的是，三个展开布拉格峰（sobp， 3 mm/3%标准）的3D伽马通过率（GPRs）为100%。此外，当比较23例铅笔束扫描（PBS）患者方案的TOPAS和TPS mc时，2mm /2%和3mm /3%标准的平均3D gpr分别为99.96%和100%。结论采用定义良好的波束源模型，我们成功地开发了一个全面的PBS MC框架。我们提出的构建PBS MC框架的方法具有构建剂量验证工具和科学研究的潜力。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Physica Medica-European Journal of Medical Physics 生物-生物物理

CiteScore

6.80

自引率

14.70%

发文量

493

审稿时长

78 days

期刊介绍： Physica Medica, European Journal of Medical Physics, publishing with Elsevier from 2007, provides an international forum for research and reviews on the following main topics: Medical Imaging Radiation Therapy Radiation Protection Measuring Systems and Signal Processing Education and training in Medical Physics Professional issues in Medical Physics.