Abstract：
Radiotherapy is part of the treatment of over 50% of cancer patients. Its efficacy is limited by the radiotoxicity to the healthy tissue. FLASH-RT is based on the biological effect that ultra-high dose rates (UHDR) and very short treatment times strongly reduce normal tissue toxicity, while preserving the anti-tumoral effect. Despite many positive preclinical results, the translation of FLASH-RT to the clinic is hampered by the lack of accurate dosimetry for UHDR beams. To date radiochromic film is commonly used for dose assessment but has the drawback of lengthy and cumbersome read out procedures. In this work, we investigate the equivalence of a 2D OSL system to radiochromic film dosimetry in terms of dose rate independency. The comparison of both systems was done using the ElectronFlash linac. We investigated the dose rate dependence by variation of the (1) modality, (2) pulse repetition frequency, (3) pulse length and (4) source to surface distance. Additionally, we compared the 2D characteristics by field size measurements. The OSL calibration showed transferable between conventional and UHDR modality. Both systems are equally independent of average dose rate, pulse length and instantaneous dose rate. The OSL system showed equivalent in field size determination within 3 sigma. We show the promising nature of the 2D OSL system to serve as alternative for radiochromic film in UHDR electron beams. However, more in depth characterization is needed to assess its full potential.
摘要：
放射治疗是超过50%癌症患者治疗的一部分。其功效受限于对健康组织的放射性毒性。FLASH-RT基于超高剂量率（UHDR）和非常短的治疗时间可大大降低正常组织毒性的生物学效应，同时保留抗肿瘤作用。尽管有许多积极的临床前结果，由于缺乏对UHDR光束的准确剂量学，因此阻碍了FLASH-RT向临床的翻译。迄今为止,放射变色胶片通常用于剂量评估,但具有冗长且繁琐的读出程序的缺点。在这项工作中,我们在剂量率独立性方面研究了2DOSL系统与辐射变色胶片剂量学的等效性。两个系统的比较是使用ElectronFlash直线加速器完成的。我们调查了（1）模态变化对剂量率的依赖性，（2）脉冲重复频率，(3)脉冲长度和(4)源到表面的距离。此外,我们通过场尺寸测量比较了2D特征。OSL校准显示可在常规模式和UHDR模式之间转移。两种系统同样独立于平均剂量率，脉冲长度和瞬时剂量率。OSL系统在3西格玛内的田间大小测定中显示出等效。我们展示了2DOSL系统的有希望的性质，可作为UHDR电子束中辐射变色膜的替代品。然而,需要更深入的表征来评估其全部潜力。
