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首页> 外文期刊>Journal of Cancer Research and Therapeutics >Commissioning of portal dosimetry using a novel method for flattening filter-free photon beam in a nontrue beam linear accelerator
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Commissioning of portal dosimetry using a novel method for flattening filter-free photon beam in a nontrue beam linear accelerator

机译：使用一种在非真光束线性加速器中展平无滤光子光束的新方法调试门控剂量法

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Aim: The aim of this study is to commission and validate the portal dosimetry (PD) system using an indirect method for flattening filter free (FFF) photon beam of the upgraded c-series linear accelerator. Background: Varian Medical System clinacs with amorphous-silicon portal imager panel (aSi-1000) do not have PD for FFF beams. Recently, our c-series linear accelerator was upgraded to deliver 6MV FFF (6MVFFF) photon beam with the highest dose rate of 1400 monitor unit (MU)/min. The study, therefore, focuses on the commissioning and validation of PD for the 6MVFFF beam. Materials and Methods: An indirect method was implemented to predict the portal dose for FFF beam in Eclipse as the treatment planning system does not have direct prediction algorithm for FFF beam (version. 11). Dosimetrical characteristics of aSi-electronic portal imaging device (EPID) were evaluated for 6MVFFF beam and validation of PD for 6MVFFF beam was performed for open fields along with pretreatment quality assurance of intensity-modulated radiation therapy (IMRT), volumetric-modulated arc therapy (VMAT), and stereotactic radiosurgery (SRS) techniques for 30 patients planned with 6MVFFF beam. Results: ASi-EPID saturates between 100 and 130 cm source to detector distance (SDD) for 6MVFFF beam and resolved at more than 140 cm SDD. The squared correlation coefficient (Rsup2/sup) for MU linearity was found to be 1 (Rsup2/sup = 1), and instantaneous dose response linearity at different SDD's was found to be 0.999 (Rsup2/sup = 0.999) for the 6MVFFF beam. Maximum gamma area index (GAI) for 3% dose difference and 3 mm distance-to-agreement criteria for IMRT, VMAT, and SRS/stereotactic radiotherapy plans was 97.9% ± 0.3%, 96.3% ± 0.5%, and 98.2% ± 0.2%, respectively. Conclusion: The results reveal that this novel method can be used to commission portal dosimetry for 6MVFFF beam as it is a convenient, faster, and accurate method.
机译：目的：本研究的目的是使用一种间接方法来扁平化升级后的c系列线性加速器的无滤波器（FFF）光子束，以调试和验证门禁剂量系统（PD）。背景：带非晶硅门禁成像器面板（aSi-1000）的Varian Medical System诊所没有FFF光束的PD。最近，我们对c系列线性加速器进行了升级，以提供最高1400监视单位（MU）/ min的剂量率的6MV FFF（6MVFFF）光子束。因此，该研究着重于6MVFFF梁的PD的调试和验证。材料和方法：由于治疗计划系统没有直接预测FFF光束的算法（版本11），因此在Eclipse中采用了一种间接方法来预测FFF光束的门剂量。对6MVFFF光束评估了aSi电子门禁成像设备（EPID）的剂量学特性，并对6MVFFF光束对PD进行了现场验证，并进行了强度调制放射治疗（IMRT），体积调制电弧治疗的预处理质量保证（ （VMAT）和立体定向放射外科（SRS）技术为30例计划使用6MVFFF光束的患者。结果：对于6MVFFF光束，ASi-EPID在100至130 cm的源到检测器距离（SDD）之间达到饱和，并在超过140 cm的SDD上分辨。 MU线性的平方相关系数（R 2 ）被发现为1（R 2 = 1），并且在不同SDD处的瞬时剂量响应线性为0.999。对于6MVFFF光束（R 2 = 0.999）。 IMRT，VMAT和SRS /立体定向放疗计划的3％剂量差异和3 mm符合协议标准的最大伽马面积指数（GAI）为97.9％±0.3％，96.3％±0.5％和98.2％±0.2 ％， 分别。结论：结果表明，该新方法可方便，快捷，准确地用于6MVFFF光束的门剂量测定。

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