探讨瓦里安加速器治疗床对放射治疗剂量的影响

Effect of VARIAN accelerator treatment couch on radiotherapy dose

目的探讨加速器治疗床在临床放射治疗中的安全性。方法将固体水模置于治疗床的中心处，改变机臂角度，从不同角度让不同能量的高能x射线穿透治疗床的各种床板，通过对比测量，计算出不同治疗床板对X射线的穿透因子。结果瓦里安加速器治疗床中的网状板对6MVX射线的穿透因子在0．981～0．997，对15MVX射线的穿透因子在0．990-0．999；延长板对6MVX射线的穿透因子在0．854～0．987，对15MVX射线的穿透因子在0．899～0．996。结论放射治疗对后野时应选用网状板，因为整个后野范围的x射线穿透因子平均在0．981～0．999，而延长板主要起延长支撑作用，而此板的X射线穿透因子最小达0．854。在同一角度下，相同床板对6MVX射线穿透因子要小于15MVX射线的，而且在相同能量x射线下，穿透因子随床板厚度的增加而减小。

Objective To investigate the safety of the VARIAN accelerator couch in radiotherapy. Methods The solid water phantom was fixed at the center of the couch plank, and changed the angle of the machine gantry. The different X-ray dose of high energy penetrated different couch plank from different angle, and the penetration factor of X-ray decline was calculated by measurement and comparison. Results The penetration factors of 6 MV and 15 MV X-ray decline were within the average of 0.981 - 0.997 and 0.990 - 0.999 respectively when the plexiglass web winder body plank in the VARIAN medical linear accelerator couch plank were used. The penetration factors of 6 MV and 15 MV X-ray decline were within the average of 0.854 - 0.987 and 0.899 - 0.996 respectively when the head extending couch plank was used.Conclusion The web couch plank should be chosen in the radiotherapy of the back field, because the dose penetration factors are within the average of 0.981 - 0.999 in the total back field. The main function of the head extending couch plank is extensible and supportable, and it would reduce the dose at least 0.854. The penetration factor of 6 MV X-ray is smaller than that of 15 MV X-ray at the same angle. The penetration factors are reducing when the thickness of the couch plank increasing, under the same energy of irradiating X-ray.