闪速放射治疗(FLASH)技术对机房屏蔽设计带来的挑战

与常规放疗技术相比, FLASH治疗技术在保护正常组织方面具有优势, 但剂量率提升100倍以上。如果按照现有标准对机房进行屏蔽设计, 将显著提升改造成本, 且仍有可能无法满足标准要求, 导致FLASH治疗技术无法开展。通过调研国内外标准及文献, 分析了FLASH治疗技术对机房屏蔽设计带来的挑战, 并着重对比了不同国家在放疗机房屏蔽设计时采用的剂量率控制标准。部分国家屏蔽设计时采用考虑实际治疗工况下的平均剂量率;我国主要采用考虑居留因子条件下的瞬时剂量率方法进行控制。如果在我国开展FLASH治疗技术, 瞬时剂量率的要求将很难满足。为了提高FLASH等高剂量率放射治疗技术, 在管理目标限值不变的前提下, 建议考虑对现有标准进行修订, 采用一定时间内的平均剂量率限值进行控制, 或增加FLASH治疗条件下的控制标准。

Challenge of shielding design for FLASH radiotherapy

Compared with conventional radiotherapy, FLASH radiotherapy has advantages in protecting normal tissues, while the dose rate is increased by more than 100 times. If the shielding design of the treatment room is carried out according to the existing standard, the thickness and cost of the shielding wall will be significantly increased, or even hardly to meet the requirement of the standards, resultsing in the failure of the application of FLASH radiotherapy. By investigating the domestic and foreign standards and literature, this paper analyzes the challenges brought by FLASH radiotherapy technology to the shielding design of radiotherapy treatment room in China. Dose rate control standards adopted by different countries in the shielding design are emphatically compared as well. In several countries, the average dose rate under the actual treatment conditions was considered in the shielding design. In China, the method of instantaneous dose rate taking acount of occupancy factor is adopted. However, if FLASH radiotherapy technology is applied, the requirement of instantaneous dose rate will be difficult to meet. In order to improve the high dose rate radiotherapy technology such as FLASH radiotherapy, the revision of the existing standards is advised if the authorized limits are not changed. To use the average dose rate limit within a certain period of time for control, or to raise the control standard in the case of flash radiotherapy, are also avaliable.