关于《放射治疗机房的辐射屏蔽规范第3部分:γ射线源放射治疗机房》(GBZ/T 201.3—2014)技术指标解析

Analysis for technical indexes of ‘Radiation shielding specification for radiotherapy room Part 3: the radiotherapy room of γ-ray sources'(GBZ/T 201. 3—2014)

目的对《放射治疗机房的辐射屏蔽规范第3部分:γ射线源放射治疗机房》(GBZ/T 201.3—2014)中的主要技术指标进行解析,为放射治疗机房的屏蔽估算和防护评价提供技术指导。方法以GBZ/T 201.3—2014标准文本为主线,结合常规γ射线源治疗机房的辐射屏蔽技术资料和屏蔽设计实例,阐释治疗机房屏蔽计算原则及屏蔽估算的考虑因素,剖析屏蔽估算方法相关技术指标。结果明确了常规γ射线源治疗机房的辐射屏蔽估算方法。60Co远距治疗机房辐射屏蔽估算中应分别针对主屏蔽区、与主屏蔽区直接相连的次屏蔽区、侧屏蔽墙、迷路外墙和机房入口考虑辐射束;后装治疗机房的屏蔽估算应考虑治疗源4π发射的γ射线对墙和室顶的直接照射及其散射辐射在机房入口处的照射;头部γ刀机房屏蔽只需考虑散射辐射,某些体部γ刀机房屏蔽还需考虑旋转照射时单个源的有用线束,两者在屏蔽计算中应尽可能利用已有实测的机房内散射辐射剂量场数据。结论 GBZ/T 201.3—2014提出的γ射线源放射治疗机房辐射屏蔽估算方法是可行的,在实际应用中应遵循屏蔽计算的基本原则,结合治疗装置的剂量学参数和治疗机房的具体物理模型以及辐射束类型等屏蔽计算影响因素,并对机房辐射屏蔽效果进行验证。

Objective The main technical indexes of‘Radiation shielding specification for radiotherapy room Part3:The radiotherapy room of γ-ray sources'(GBZ/T 201.3—2014) were analyzed to provide technical guidance for shielding estimation and protection assessment of radiotherapy rooms.Methods The shielding calculation principles and the factors to be considered in shielding evaluation for radiotherapy room were interpreted and the related technical criteria in the shielding evaluation method were analyzed,based on the texts of GBZ/T 201.3—2014 and radiation shielding technical data from shielding design cases of normal radiotherapy room with γ-ray sources.Results The method for shielding evaluation were identified for normal radiotherapy rooms with γ-ray sources.The radiation beams from primary shielding area,second shielding area adjacent to primary shielding area,side shielding wall,outer wall of maze and entrance of room should be taken into account in the course of radiation shielding evaluation of ^(60)Co teletherapy room,respectively.The direct exposure from primary4π γ-ray to the wall and ceiling,and the exposure from scattering radiation to the room entrance should be taken consideration into the shielding evaluation for the after-loading brachytherapy room.Only scattering radiation shielding should be calculated for the room of head γ-knife,while useful beam from single radiation source must be taken into consideration for some body γ-knife rooms.The actual data of scattering radiation dose field in the radiotherapy room should be adopted in shielding calculation of all of γ-knife room as far as possible.Conclusion The radiation shielding evaluation method issued in GBZ/T 201.3-2014 for radiotherapy room with γ-ray sources is feasible,but the basic principles of shielding calculation should be adhere to the practice application.The impact factors for shielding calculation such as dosimetric parameters of radiotherapy facilities,concrete physical mode of radiotherapy room and radiation beam type should be combined,and the radiation protection effect of room shielding should be validated.