Department of Industrial Engineering, University of Rome Tor Vergata, Rome, Italy.
SIT S.p.A., Latina, Italy.
Med Phys. 2022 Aug;49(8):5513-5522. doi: 10.1002/mp.15782. Epub 2022 Jun 16.
A diamond detector prototype was recently proposed by Marinelli et al. (Medical Physics 2022, https://doi.org/10.1002/mp.15473) for applications in ultrahigh-dose-per-pulse (UH-DPP) and ultrahigh-dose-rate (UH-DR) beams, as used in FLASH radiotherapy (FLASH-RT). In the present study, such so-called flashDiamond (fD) was investigated from the dosimetric point of view, under pulsed electron beam irradiation. It was then used for the commissioning of an ElectronFlash linac (SIT S.p.A., Italy) both in conventional and UH-DPP modalities.
Detector calibration was performed in reference conditions, under Co and electron beam irradiation. Its response linearity was investigated in UH-DPP conditions. For this purpose, the DPP was varied in the 1.2-11.9 Gy range, by changing either the beam applicator or the pulse duration from 1 to 4 μs. Dosimetric validation of the fD detector prototype was then performed in conventional modality, by measuring percentage depth dose (PDD) curves, beam profiles, and output factors (OFs). All such measurements were carried out in a motorized water phantom. The obtained results were compared with the ones from commercially available dosimeters, namely, a microDiamond, an Advanced Markus ionization chamber, a silicon diode detector, and EBT-XD GAFchromic films. Finally, the fD detector was used to fully characterize the 7 and 9 MeV UH-DPP electron beams delivered by the ElectronFlash linac. In particular, PDDs, beam profiles, and OFs were measured, for both energies and all the applicators, and compared with the ones from EBT-XD films irradiated in the same experimental conditions.
The fD calibration coefficient resulted to be independent from the investigated beam qualities. The detector response was found to be linear in the whole investigated DPP range. A very good agreement was observed among PDDs, beam profiles, and OFs measured by the fD prototype and reference detectors, both in conventional and UH-DPP irradiation modalities.
The fD detector prototype was validated from the dosimetric point of view against several commercial dosimeters in conventional beams. It was proved to be suitable in UH-DPP and UH-DR conditions, for which no other commercial real-time active detector is available to date. It was shown to be a very useful tool to perform fast and reproducible beam characterizations in standard clinical motorized water phantom setups. All of the previously mentioned demonstrate the suitability of the proposed detector for the commissioning of UH-DR linac beams for preclinical FLASH-RT applications.
马林内利等人最近提出了一种钻石探测器原型，用于超高剂量脉冲（UH-DPP）和超高剂量率（UH-DR）射线，如在 FLASH 放射治疗（FLASH-RT）中使用。在本研究中，这种所谓的 flashDiamond（fD）从剂量学的角度进行了研究，在脉冲电子束照射下。然后，它被用于电子 Flash 直线加速器（意大利 SIT S.p.A.）的常规和 UH-DPP 模式的调试。
在 Co 和电子束照射下，在参考条件下对探测器进行校准。研究了在 UH-DPP 条件下的探测器响应线性度。为此，通过改变束流敷贴器或脉冲持续时间（从 1 到 4μs），在 1.2-11.9 Gy 的范围内改变 DPP。在常规模式下，通过测量百分深度剂量（PDD）曲线、束流轮廓和输出因子（OF），对 fD 探测器原型进行了剂量验证。所有这些测量都是在一个机动水模体中进行的。将获得的结果与市售的剂量计（即 microDiamond、Advanced Markus 电离室、硅二极管探测器和 EBT-XD GAFchromic 胶片）进行了比较。最后，fD 探测器用于完全表征 ElectronFlash 直线加速器提供的 7 和 9 MeV UH-DPP 电子束。特别是，测量了两种能量和所有敷贴器的 PDD、束流轮廓和 OF，并与在相同实验条件下照射的 EBT-XD 胶片的结果进行了比较。
fD 校准系数与所研究的束质无关。在整个研究的 DPP 范围内，探测器的响应被发现是线性的。fD 原型和参考探测器在常规和 UH-DPP 照射模式下测量的 PDD、束流轮廓和 OF 之间观察到非常好的一致性。
fD 探测器原型在常规束方面已针对几种商业剂量计从剂量学角度进行了验证。它被证明适用于 UH-DPP 和 UH-DR 条件，到目前为止，还没有其他商用实时主动探测器可用。它被证明是在标准临床机动水模体设置中进行快速和可重复的束特性分析的非常有用的工具。所有这些都证明了所提出的探测器在为临床前 FLASH-RT 应用的 UH-DR 直线加速器束的调试中的适用性。
