Comprehensive characterization and validation of a fast-resolving (1000 Hz) plastic scintillator for ultra-high dose rate electron dosimetry

IF 3.2 2区医学 Q1 RADIOLOGY, NUCLEAR MEDICINE & MEDICAL IMAGING

Medical physics Pub Date : 2025-09-22 DOI:10.1002/mp.70006

Lixiang Guo, Banghao Zhou, Yi-Chun Tsai, Kai Jiang, Viktor Iakovenko, Ken Kang-Hsin Wang

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引用次数: 0

Abstract

Background

The normal tissue sparing effect of ultra-high dose rate irradiation (≥40 Gy/s, UHDR), as compared to conventional dose rate (CONV), has attracted significant research interest for FLASH radiotherapy (RT). Accurate, dose rate independent, fast-responding dosimeters capable of resolving the spatiotemporal characteristics of UHDR beams are urgently needed to facilitate FLASH research and support its clinical translation. Tissue-equivalent scintillators, with millimeter-level spatial resolution and millisecond-level temporal resolution, possess these required characteristics and show strong potential for use in UHDR dosimetry.

Purpose

We investigated the performance of the HYPERSCINT RP-FLASH scintillator system at up to 1000 Hz sampling frequency (f_s) for UHDR electron beam dosimetry.

Methods

The scintillator was exposed to CONV and UHDR electron irradiation using a LINAC-based FLASH platform. Its spectral characteristics were delineated with a four-component calibration, followed by a signal-to-dose calibration using 18 MeV CONV electron beam. The dose linearity and dosimetric accuracy in response to CONV and UHDR irradiation at 1 and 1000 Hz f_s were quantified against ion chamber and EBT-XD film measurements. The response of the scintillator system was investigated as a function of beam energy (6 and 18 MeV), field size (2 × 2 to 25 × 25 cm²), dose per pulse (DPP, 0.8–2.3 Gy/pulse), and pulse repetition frequency (PRF, 30–180 Hz). Relative signal sensitivity was quantified against accumulated dose to account for the scintillator's radiation degradation. Pulse-resolved dose measurements at 18 MeV UHDR, obtained using the scintillator with 1000 Hz f_s for a train of 10 pulses at 180 Hz PRF, were validated with a PMT-fiber optic scattered radiation detector.

Results

The scintillator system at 1 Hz f_s demonstrated high accuracy in dose measurements, remaining within 0.5% of ion chamber measurements over the dose range of 0.1–35 Gy under CONV irradiation. For the UHDR irradiation, the scintillator showed <3% dose error compared to film measurements up to 40 Gy at 1000 Hz f_s. Its response was found to be minimally dependent on energy, field size, and PRF. The scintillator under-responded by ∼4% over the 0.8–2.3 Gy/pulse range, although the dose difference relative to film remained within 2%. The radiation degradation of the scintillation detector followed a 2^nd-order polynomial fit between 0 and 10 kGy, and a linear fit with a slope of −2.6%/kGy in the range of 0–2 kGy. The pulse-resolved dose measured by the scintillator was verified to be within 3% accuracy when compared to the measurements obtained using the PMT-fiber optic detector.

Conclusions

With routine dose calibration to account for radiation induced degradation, the fast-responding scintillator system can accurately provide millisecond-resolved inter-pulse measurements for electron beams at conventional and ultra-high dose rates, with minimal dependence on beam parameters. This suggests that the HYPERSCINT RP-FLASH scintillator system could serve as a detector of choice for electron FLASH research.

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用于超高剂量率电子剂量测定的快速分辨（1000 Hz）塑料闪烁体的综合表征和验证

与常规剂量率（CONV）相比，超高剂量率（≥40 Gy/s， UHDR）对正常组织的保护作用已经引起了FLASH放疗（RT）的重要研究兴趣。为了促进FLASH研究并支持其临床应用，迫切需要能够解析超高dr光束时空特征的准确、剂量率独立、快速响应的剂量计。具有毫米级空间分辨率和毫秒级时间分辨率的组织等效闪烁体具有这些所需的特性，并显示出在UHDR剂量学中使用的强大潜力。目的研究了HYPERSCINT RP-FLASH闪烁体系统在高达1000 Hz采样频率下用于UHDR电子束剂量测定的性能。方法采用基于linac的FLASH平台对闪烁体进行CONV和UHDR电子照射。通过四组分校准描述了其光谱特性，然后使用18mev CONV电子束进行了信号-剂量校准。通过离子室和EBT-XD薄膜测量，定量了1和1000 Hz频率下CONV和UHDR辐照的剂量线性和剂量学精度。研究了闪烁体系统的响应随光束能量（6和18 MeV）、场大小（2 × 2 ~ 25 × 25 cm2）、脉冲剂量（DPP, 0.8 ~ 2.3 Gy/脉冲）和脉冲重复频率（PRF, 30 ~ 180 Hz）的变化规律。相对信号灵敏度与累积剂量进行了量化，以解释闪烁体的辐射退化。用pmt光纤散射辐射探测器验证了在180 Hz PRF下，使用1000 Hz的闪烁体对10列脉冲进行18 MeV UHDR的脉冲分辨剂量测量。结果在CONV辐照下，在0.1 ~ 35 Gy剂量范围内，闪烁体系统的剂量测量精度在离子室测量精度的0.5%以内。对于UHDR辐射，闪烁体显示了与薄膜测量值相比的<；3%的剂量误差，在1000 Hz fs下高达40 Gy。研究发现，其响应对能量、场大小和PRF的依赖最小。闪烁体在0.8-2.3 Gy/脉冲范围内响应不足约4%，尽管相对于薄膜的剂量差保持在2%以内。闪烁探测器的辐射衰减在0 ~ 10 kGy范围内服从二阶多项式拟合，在0 ~ 2 kGy范围内服从斜率为−2.6%/kGy的线性拟合。与使用pmt光纤探测器获得的测量结果相比，闪烁体测量的脉冲分辨剂量被证实精度在3%以内。快速响应闪烁体系统通过常规剂量校准来解释辐射引起的退化，可以在常规和超高剂量率下准确地提供毫秒级分辨的电子束脉冲间测量，对光束参数的依赖最小。这表明HYPERSCINT RP-FLASH闪烁体系统可以作为电子FLASH研究的首选探测器。

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

Medical physics 医学-核医学

CiteScore

6.80

自引率

15.80%

发文量

660

审稿时长

1.7 months

期刊介绍： Medical Physics publishes original, high impact physics, imaging science, and engineering research that advances patient diagnosis and therapy through contributions in 1) Basic science developments with high potential for clinical translation 2) Clinical applications of cutting edge engineering and physics innovations 3) Broadly applicable and innovative clinical physics developments Medical Physics is a journal of global scope and reach. By publishing in Medical Physics your research will reach an international, multidisciplinary audience including practicing medical physicists as well as physics- and engineering based translational scientists. We work closely with authors of promising articles to improve their quality.