国内首台单间室质子治疗系统场所辐射水平的测量与评估

Measurements and assessment of radiation levels at the radiotherapy site of the first domestic single-vault proton therapy system

目的:测量并评估国内首台单间室质子治疗系统场所内的相关辐射剂量。方法:测量治疗系统出束时和停束后治疗场所的辐射水平,并评估场所内人员年有效剂量。结果:出束过程中,探测到最高辐射剂量在设备层防护门处,γ辐射水平为2.140μSv/h,中子辐射水平为0.850μSv/h。束流停止后,中子辐射随即消失,活化产物的辐射以γ射线为主,同一地点停束时间越长,感生辐射强度越低。同一时间与受照物体的距离越远,感生辐射强度越低。评估所有人员受照年有效剂量均处于安全水平,其中物理师最高,为2.138 mSv。结论:本中心质子治疗场所辐射水平符合要求,可以安全开展质子治疗工作。

Objective To measure and assess relevant radiation doses at the radiotherapy site of the first domestic single-vault proton therapy system.Methods The radiation levels of the therapy system during and after beam irradiation were measured,and annual effective doses were assessed for personnel at the site.Results During beam irradiation,the highest radiation dose was detected at the shielded door of the equipment floor,with a gamma radiation level of 2.140μSv/h and a neutron radiation level of 0.850μSv/h.Neutron radiation disappeared immediately once the beams stopped.In contrast,the radiation activated originated mostly from gamma rays.A longer time after beams stopped was associated with lower induced radiation intensity at the same location.Furthermore,a farther distance from the irradiated object corresponded to lower induced radiation intensity at the same time.The assessment result reveal that the annual effective doses to the personnel were at the safe level,with physicists exposed to the highest dose of 2.138 mSv.Conclusions The radiation level at the studied proton therapy site meets the safety requirement,and the treatment can be performed safely at this site.