The emergent FLASH RadioTherapy (RT) uses ultrahigh dose-rate irradiation (up to 10⁷ Gy/s instantaneous dose-rate in each μs pulse) to deliver a single high dose of irradiation in a very short time (<200 ms). Pre-clinical studies at ultrahigh dose-rates recently showed an increased ratio between tumoricidal effect and normal tissue toxicity (therapeutic index), compared to conventional RT at standard Gy/min dose-rates. If confirmed by biological in vivo validations, this could represent a breakthrough in cancer treatment. However, the reliability and the accuracy of experimental studies are nowadays limited by the lack of detectors able to measure online the beam fluence at FLASH dose-rates. The behavior of standard beam monitors (gas-filled ionization chambers) is compromised by the volume recombination caused by the amount of charges created per unit volume and unit time, due to the large dose-rate. Moreover, due to the lack of proper monitoring devices and to the uncertainties of its future applications, very few facilities are able to deliver at present FLASH irradiations. In this contribution, we report about the physical and technological challenges of monitoring high and ultra-high dose-rates with electrons and photon beams, starting from the pre-clinical and clinical constraints for new devices. Based on the extensive experience in silicon detectors for monitoring applications in RT with external beams, the work then investigates silicon sensors as a possible option to tackle such extreme requirements and a rugged thin and large (e.g., 10 × 10 cm²) flat detector (silicon-based sensor + readout electronics) is therefore outlined. This study aims at presenting the FLASH-RT dosimetry problem and analyzing the possibilities for a silicon sensor to be employed as sensing device for several FLASH scenarios, including some ideas on the readout part. However, more detailed simulations and studies are demanded to delineate more precisely the technical choices to be undertaken in order to tackle the clinical accuracy required on the beam fluence, typically a few %, during photon and electron high and ultra-high irradiations, the required minimal perturbation of the beam and the high level of radiation resistance.

新兴的FLASH放射疗法（RT）使用超高剂量率辐射（每个μs脉冲高达10 ⁷ Gy / s的瞬时剂量率）在非常短的时间内（<200 ms）提供一次高剂量辐射。最近的临床前研究表明，与常规RT在标准Gy / min剂量率下相比，超高剂量率的杀肿瘤效果与正常组织毒性（治疗指数）之间的比率有所增加。如果经生物学证实体内验证，这可能代表癌症治疗方面的突破。但是，由于缺乏能够以FLASH剂量率在线测量束通量的检测器，如今实验研究的可靠性和准确性受到限制。由于大剂量率，单位体积和单位时间产生的电荷量导致体积重新组合，从而损害了标准束监视器（充满气体的电离室）的性能。此外，由于缺乏适当的监视设备以及其未来应用的不确定性，目前仅有很少的设施能够提供闪光灯照射。在这项贡献中，我们报告了用电子和光子束监测高和超高剂量率时的物理和技术挑战，从新设备的临床前和临床约束开始。基于在用于外部射线监测RT应用的硅探测器方面的丰富经验，该工作随后研究了硅传感器作为解决此类极端要求以及坚固耐用的薄型和大型（例如10×10 cm）的可能选择²）因此概述了平面检测器（基于硅的传感器+读出电子设备）。这项研究的目的是提出FLASH-RT剂量学问题，并分析将硅传感器用作几种FLASH场景的传感设备的可能性，包括有关读出部分的一些想法。但是，需要更详细的模拟和研究来更精确地描述要进行的技术选择，以解决在高光子和电子辐照和电子超高辐照期间光束注量所需的临床精度，通常为百分之几。光束干扰最小，辐射强度高。