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目的探讨放射治疗机房中有用束主屏蔽区的宽度的计算方法。方法按照国家标准《放射治疗机房的辐射屏蔽规范》计算出有用束主屏蔽区的宽度,与准直器角度为45°,机架角为135°时的治疗束到墙最大射野宽度比较;并在某医院加速器机房实测辐射防护。结果按照国家标准计算的有用束主屏蔽区宽度比最大射野宽度小,理论上存在射线泄露区域,实测结果也证实理论上的射线泄露区域确实存在。结论国家标准中放射治疗机房的有用束主屏蔽区的宽度计算方法及监测条件仅仅考虑机架角为90°、180°或者270°的情况,考虑的情况不足,存在防护漏洞。据此本文推导出正确的有用束主屏蔽区的宽度计算方法,并给出已建放射治疗机房的补救方法。
Objective To explore the method of calculating the width of the main shielding zone of useful beam in radiotherapy room. Methods According to the national standard “Radiation Shielding Room for Radiation Therapy,” the width of the main shielding zone of the useful beam was calculated and compared with the maximum width of the beam from the treatment beam to the wall when the collimator angle was 45 ° and the gantry angle was 135 °. And in a hospital accelerator room measured radiation protection. Results According to the national standard, the width of the main shielding zone of the useful beam is smaller than that of the maximum beam width. There is theoretically a ray leakage area. The measured results also confirm that the theoretical ray leakage area does exist. Conclusion The calculation method and monitoring conditions of the width of the main shielding zone of the useful beam in the radiotherapy room in the national standard only consider the situation where the frame angle is 90 °, 180 ° or 270 °. Considering the situation is insufficient, there are protective loopholes. Based on this, we derive the correct method of calculating the width of the main shielding zone of useful beam and give the remedies of the existing radiation therapy room.