Pre-irradiation dose requirements for reference-class ionization chambers: Quantifying measurement stability

IF 2.2 4区医学 Q3 RADIOLOGY, NUCLEAR MEDICINE & MEDICAL IMAGING

Journal of Applied Clinical Medical Physics Pub Date : 2025-09-29 DOI:10.1002/acm2.70273

Takumi Yamada, Kazuki Mayumi, Satoshi Tanabe, Takayuki Nishikata, Naoki Kinoshita, Tatsuya Sakai, Hironori Sakai, Tetsuya Oka, Hiroyuki Ishikawa, Tsutomu Kanazawa

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引用次数: 0

Abstract

Background

Pre-irradiation of ionization chambers is widely recommended to stabilize output readings for reference dosimetry in radiation therapy. However, the specific pre-irradiation requirements for different chamber models, particularly under strictly controlled conditions that isolate chamber performance, remain unclear.

Purpose

This study aimed to quantitatively evaluate the pre-irradiation dose required to stabilize the output of various reference-class ionization chambers, while minimizing the influence of environmental and system-level uncertainties.

Methods

Twelve reference-class ionization chambers (Exradin A12, A1SL; IBA CC13, FC65G; PTW 30013, 31021) were evaluated under strictly controlled conditions (room temperature: 25 ± 1°C, water temperature: 25.00 ± 0.01°C, relative humidity: approximately 50%). Output stability was assessed using a 10 MV photon beam from a TrueBeam linac. Chamber readings were measured using an RT521R2 electrometer and normalized to an adjacent external monitor chamber. Readings are defined as stable if the reading variation is <0.1% and does not exhibit any trending. The optimal number of pre-irradiation exposures and corresponding doses were determined for each chamber.

Results

For the large-volume chambers (Exradin A12, IBA FC65G, PTW 30013), output variation was within ±0.05% from the first irradiation, suggesting that pre-irradiation may be unnecessary. In contrast, the middle-volume class ionization chambers (Exradin A1SL, IBA CC13, PTW 31021) exhibited variations of up to ±0.25%, and required up to 100 MU × 25 (approximately 21.25 Gy) of pre-irradiation to achieve stability under the controlled experimental conditions of this study.

Conclusions

This study demonstrated that the required pre-irradiation dose varies depending on the type of ionization chamber, and that the output variation is significantly lower than the previously reported 1%. These results may help streamline clinical reference dosimetry by tailoring procedures to each chamber.

Abstract Image

查看原文本刊更多论文

参考级电离室辐照前剂量要求：定量测量稳定性。

背景：在放射治疗中，电离室的预照射被广泛推荐用于稳定参考剂量测定的输出读数。然而，对于不同的腔室模型，特别是在隔离腔室性能的严格控制条件下，具体的辐照前要求仍不清楚。目的：本研究旨在定量评估稳定各种参考级电离室输出所需的辐照前剂量，同时尽量减少环境和系统级不确定性的影响。方法：在严格控制的条件下（室温：25±1°C，水温：25.00±0.01°C，相对湿度：约50%）对12个标准级电离室（Exradin A12, A1SL; IBA CC13, FC65G; PTW 30013, 31021）进行评价。使用来自TrueBeam直线加速器的10 MV光子束来评估输出稳定性。使用RT521R2静电计测量腔室读数，并将其归一化到相邻的外部监测腔室。结果：对于大容量腔室（Exradin A12, IBA FC65G, PTW 30013），输出变化在第一次照射的±0.05%范围内，表明可能不需要预照射。相比之下，中等体积级电离室（Exradin A1SL, IBA CC13, PTW 31021）的变化幅度高达±0.25%，在本研究的受控实验条件下，需要高达100 MU × 25（约21.25 Gy）的预辐照才能达到稳定。结论：本研究表明，所需的辐照前剂量随电离室类型的不同而变化，且输出变化明显低于先前报道的1%。这些结果可能有助于简化临床参考剂量测定，为每个腔量身定制程序。

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

Journal of Applied Clinical Medical Physics 医学-核医学

CiteScore

3.60

自引率

19.00%

发文量

331

审稿时长

3 months

期刊介绍： Journal of Applied Clinical Medical Physics is an international Open Access publication dedicated to clinical medical physics. JACMP welcomes original contributions dealing with all aspects of medical physics from scientists working in the clinical medical physics around the world. JACMP accepts only online submission. JACMP will publish: -Original Contributions: Peer-reviewed, investigations that represent new and significant contributions to the field. Recommended word count: up to 7500. -Review Articles: Reviews of major areas or sub-areas in the field of clinical medical physics. These articles may be of any length and are peer reviewed. -Technical Notes: These should be no longer than 3000 words, including key references. -Letters to the Editor: Comments on papers published in JACMP or on any other matters of interest to clinical medical physics. These should not be more than 1250 (including the literature) and their publication is only based on the decision of the editor, who occasionally asks experts on the merit of the contents. -Book Reviews: The editorial office solicits Book Reviews. -Announcements of Forthcoming Meetings: The Editor may provide notice of forthcoming meetings, course offerings, and other events relevant to clinical medical physics. -Parallel Opposed Editorial: We welcome topics relevant to clinical practice and medical physics profession. The contents can be controversial debate or opposed aspects of an issue. One author argues for the position and the other against. Each side of the debate contains an opening statement up to 800 words, followed by a rebuttal up to 500 words. Readers interested in participating in this series should contact the moderator with a proposed title and a short description of the topic