为 FLASH RT 临床前动物实验和未来的临床人类方案，委托建造超高压率脉冲电子束医用 LINAC。

Commissioning of an ultra-high dose rate pulsed electron beam medical LINAC for FLASH RT preclinical animal experiments and future clinical human protocols.

机构信息

Institute of Radiation Physics, Lausanne University Hospital and Lausanne University, Rue du Grand-Pré 1, Lausanne, CH-1007, Switzerland.

Radio-Oncology Department, Lausanne University Hospital and Lausanne University, Rue du Bugnon 46, Lausanne, CH-1011, Switzerland.

出版信息

Med Phys. 2021 Jun;48(6):3134-3142. doi: 10.1002/mp.14885. Epub 2021 May 14.

DOI:10.1002/mp.14885

PMID:33866565

Abstract

PURPOSE

To present the acceptance and the commissioning, to define the reference dose, and to prepare the reference data for a quality assessment (QA) program of an ultra-high dose rate (UHDR) electron device in order to validate it for preclinical animal FLASH radiotherapy (FLASH RT) experiments and for FLASH RT clinical human protocols.

METHODS

The Mobetron device was evaluated with electron beams of 9 MeV in conventional (CONV) mode and of 6 and 9 MeV in UHDR mode (nominal energy). The acceptance was performed according to the acceptance protocol of the company. The commissioning consisted of determining the short- and long-term stability of the device, the measurement of percent depth dose curves (PDDs) and profiles at two different positions (with two different dose per pulse regimen) and for different collimator sizes, and the evaluation of the variability of these parameters when changing the pulse width and pulse repetition frequency. Measurements were performed using a redundant and validated dosimetric strategy with alanine and radiochromic films, as well as Advanced Markus ionization chamber for some measurements.

RESULTS

The acceptance tests were all within the tolerances of the company's acceptance protocol. The linearity with pulse width was within 1.5% in all cases. The pulse repetition frequency did not affect the delivered dose more than 2% in all cases but 90 Hz, for which the larger difference was 3.8%. The reference dosimetry showed a good agreement within the alanine and films with variations of 2.2% or less. The short-term (resp. long-term) stability was less than 1.0% (resp. 1.8%) and was the same in both CONV and UHDR modes. PDDs, profiles, and reference dosimetry were measured at two positions, providing data for two specific dose rates (about 9 Gy/pulse and 3 Gy/pulse). Maximal beam size was 4 and 6 cm at 90% isodose in the two positions tested. There was no difference between CONV and UHDR mode in the beam characteristics tested.

CONCLUSIONS

The device is commissioned for FLASH RT preclinical biological experiments as well as FLASH RT clinical human protocols.

摘要

目的

介绍验收和调试过程，确定参考剂量，并为超高压率（UHDR）电子设备的质量评估（QA）计划准备参考数据，以便验证其在临床前动物FLASH 放射治疗（FLASH RT）实验和临床人类 FLASH RT 协议中的应用。

方法

采用 9 MeV 的电子束在常规（CONV）模式和 6 MeV 和 9 MeV 的 UHDR 模式（标称能量）下对 Mobetron 设备进行评估。验收工作按照公司的验收协议进行。调试工作包括确定设备的短期和长期稳定性、在两个不同位置（使用两种不同的脉冲剂量方案）和不同准直器尺寸下测量百分深度剂量曲线（PDD）和剂量分布曲线，并评估改变脉冲宽度和脉冲重复频率时这些参数的变化。测量工作采用冗余且经过验证的剂量学策略，使用丙氨酸和放射色胶片以及 Advanced Markus 电离室进行部分测量。

结果

验收测试均符合公司验收协议的公差要求。在所有情况下，线性度与脉冲宽度的偏差均在 1.5%以内。在所有情况下，脉冲重复频率对剂量的影响均不超过 2%，但在 90 Hz 时，最大偏差为 3.8%。参考剂量学在丙氨酸和胶片中具有良好的一致性，变化幅度小于 2.2%。短期（长期）稳定性均小于 1.0%（1.8%），在 CONV 和 UHDR 模式下相同。在两个位置测量了 PDD、剂量分布曲线和参考剂量学，为两个特定剂量率（约 9 Gy/脉冲和 3 Gy/脉冲）提供了数据。在测试的两个位置，最大束流尺寸在 90%等剂量线处为 4 cm 和 6 cm。在测试的束流特性方面，CONV 和 UHDR 模式之间没有差异。