Dosimetric saturation effect study and correction calculation method of ionization chamber at ultra-high dose rate (FLASH)

IF 2.8 3区物理与天体物理 Q3 CHEMISTRY, PHYSICAL

Radiation Physics and Chemistry Pub Date : 2024-10-22 DOI:10.1016/j.radphyschem.2024.112344

Xinle Lang , Zhenguo Hu , Min Li , Kai Tang , Juan Li , Faming Luo , Zhiguo Xu , Ruishi Mao , Chuan Huang , Jiali Fu , Zulong Zhao , Guoqing Xiao

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引用次数: 0

Abstract

Background

and Purpose: FLASH radiotherapy has aroused strong interest among researchers, but how to monitor dose in real time and lack of generally accepted ion correction model are one of the challenges. This study is based on previous research work, the dosimetric verification of FLASH ionization chamber was performed using a 200 keV electron beam irradiation platform at an ultra-high dose rate. At the same time, the finite element program is written to analyze and calculate the ion correction factor. In addition, the results are compared with the calculation results of Boag model.

Methods

In this study, the pressure of the sensitive volume in the detector was adjusted to 16 mbar for the purpose of dosimetry of dose rates in excess of 100 Gy/s. In order to monitor the response of the detector, the beam frequency and pulse width were adjusted accordingly. However, due to the saturation effect of the ionization chamber, the processes of electron ion pair drift, attachment, recombination and diffusion in the sensitive volume were modelled on the basis of the relevant physical principles. Finally, the correction factor was calculated by the finite element analysis.

Results

The experimental results demonstrate that the FLASH ionization chamber is capable of meeting the requirements of dose measurement and beam monitoring of the electron beam at ultra-high dose rates. Furthermore, the analytical model is able to more accurately describe the saturation effect and calculate the correction factor.

Conclusion

In this paper, the method of reducing air pressure is employed for the purpose of monitoring the dose of ultra-high dose rate. Simultaneously, the finite element method was employed to analyze the physical process of electron–ion pairs within the chamber and to calculate the ion correction factor analytically. A comparison with the Boag model indicates that the proposed approach is effective. However, the results exhibit a certain degree of divergence from experimental outcomes. This discrepancy may be attributed to the influence of the input parameters, which require further calibration to enhance the accuracy and the robustness of the model.

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超高剂量率电离室（FLASH）的剂量饱和效应研究和修正计算方法

背景与目的：FLASH放射治疗引起了研究人员的强烈兴趣，但如何实时监测剂量以及缺乏公认的离子校正模型是难题之一。本研究在前期研究工作的基础上，利用 200 keV 电子束辐照平台在超高剂量率下对 FLASH 电离室进行了剂量学验证。同时，编写了有限元程序来分析和计算离子校正因子。方法在这项研究中，为了对超过 100 Gy/s 的剂量率进行剂量测定，探测器中敏感容积的压力被调整为 16 mbar。为了监测探测器的反应，光束频率和脉冲宽度也做了相应的调整。然而，由于电离室的饱和效应，电子离子对的漂移、附着、重组和在敏感体积内的扩散过程都是根据相关的物理原理模拟的。实验结果表明，FLASH 电离室能够满足超高剂量率下的剂量测量和电子束监测要求。结论本文采用减小气压的方法来监测超高剂量率的剂量。同时，采用有限元法分析了腔体内电子-离子对的物理过程，并对离子校正因子进行了分析计算。与 Boag 模型的比较表明，所提出的方法是有效的。然而，计算结果与实验结果存在一定程度的偏差。这种差异可能是由于输入参数的影响，需要进一步校准以提高模型的准确性和稳健性。

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

Radiation Physics and Chemistry 化学-核科学技术

CiteScore

5.60

自引率

17.20%

发文量

574

审稿时长

12 weeks

期刊介绍： Radiation Physics and Chemistry is a multidisciplinary journal that provides a medium for publication of substantial and original papers, reviews, and short communications which focus on research and developments involving ionizing radiation in radiation physics, radiation chemistry and radiation processing. The journal aims to publish papers with significance to an international audience, containing substantial novelty and scientific impact. The Editors reserve the rights to reject, with or without external review, papers that do not meet these criteria. This could include papers that are very similar to previous publications, only with changed target substrates, employed materials, analyzed sites and experimental methods, report results without presenting new insights and/or hypothesis testing, or do not focus on the radiation effects.