Department of Radiation Oncology, University Hospital Zurich and University of Zurich, Zurich, Switzerland.
Department of Radiation Oncology, University Hospital Zurich and University of Zurich, Zurich, Switzerland.
Radiother Oncol. 2023 Oct;187:109822. doi: 10.1016/j.radonc.2023.109822. Epub 2023 Jul 27.
Radiotherapy delivery with ultra-high dose rates (UHDR) has consistently produced normal tissue sparing while maintaining efficacy for tumour control in preclinical studies, known as the FLASH effect. Modified clinical electron linacs have been used for pre-clinical studies at reduced source-surface distance (SSD) and novel intra-operative devices are becoming available. In this context, we modified a clinical linac to deliver 16 MeV UHDR electron beams with an isocentric setup.
The first Varian TrueBeam (SN 1001) was clinically operative between 2009-2022, it was then decommissioned and converted into a research platform. The 18 MeV electron beam was converted into the experimental 16 MeV UHDR. Modifications were performed by Varian and included a software patch, thinner scattering foil and beam tuning. The dose rate, beam characteristics and reproducibility were measured with electron applicators at SSD = 100 cm.
The dose per pulse at isocenter was up to 1.28 Gy/pulse, corresponding to average and instantaneous dose rates up to 256 Gy/s and 3⋅10 Gy/s, respectively. Beam characteristics were equivalent between 16 MeV UHDR and conventional for field sizes up to 10x10cm and an overall beam reproducibility within ± 2.5% was measured.
We report on the first technical conversion of a Varian TrueBeam to produce 16 MeV UHDR electron beams. This research platform will allow isocenter experiments and deliveries with conventional setups up to field sizes of 10x10 cm within a hospital environment, reducing the gap between preclinical and clinical electron FLASH investigations.
超高剂量率（UHDR）放射治疗在临床前研究中始终能够实现对正常组织的保护，同时保持肿瘤控制的疗效，这被称为FLASH 效应。经过修改的临床电子直线加速器已应用于降低源皮距（SSD）的临床前研究，并且新型术中设备也正在普及。在此背景下，我们对一台临床直线加速器进行了改装，使其在等中心位置产生 16 MeV 的 UHDR 电子束。
首台瓦里安 TrueBeam（SN 1001）于 2009 年至 2022 年期间投入临床使用，随后退役并改装为研究平台。18 MeV 电子束被转换为实验用的 16 MeV UHDR。瓦里安公司对其进行了多项修改，包括软件补丁、更薄的散射箔片以及束流调整。在 SSD = 100 cm 处，使用电子适形器测量剂量率、束流特性和重复性。
等中心处的每个脉冲剂量高达 1.28 Gy/脉冲，对应的平均和瞬时剂量率分别高达 256 Gy/s 和 3⋅10 Gy/s。在 16 MeV UHDR 和常规条件下，对于 10x10 cm 大小的射野，束流特性相当，并且测量到的整体束流重复性在 ± 2.5%以内。
我们报告了首台瓦里安 TrueBeam 临床直线加速器改装为产生 16 MeV UHDR 电子束的技术。该研究平台将允许在医院环境中进行等中心实验和常规设置的治疗，治疗射野大小可达 10x10 cm，从而缩小临床前和临床电子 FLASH 研究之间的差距。
