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目的通过测量医用直线加速器放射治疗射野外低剂量辐射场的剂量,建立射野外低剂量辐射场的剂量分布模型。方法用环境剂量巡测仪测量医用直线加速器在治疗射野外的GT方向和左右向的不同距离的剂量,测量不同射野时射野外离等中心点100处的剂量;测量不同型号的加速器射野外低剂量辐射场的剂量分布,比较不同加速器间的射野外低剂量辐射场的剂量分布差别。测量数据进行统计学分析。结果 10cm×10cm放疗射野外70cm范围内,GT方向的散射线剂量与侧向的相同点的散射线剂量差别不大,相对均匀,70cm以上,逐渐降低;射野外低剂量辐射场的剂量随射野的增大而增加;射野外低剂量辐射场的剂量随加速器出束MU数的增加而增加;同一厂家生产的同类不同型号的加速器散射线剂量分布基本相同。结论放疗患者所处的低剂量散射线辐射场剂量分布是在放疗射野外一定范围相对均匀,且随射野增大和出束MU数的增加而增加,患者在接受根治性肿瘤放疗时,除射野穿透部位以外,躯干处于一个相对均匀的散射线辐射场中,特别是年轻患者所受剂量有必要予以评估。
OBJECTIVE To establish the dose distribution model of low-dose radiation fields in the field by measuring the dose of low-dose radiation field outside the field of medical linear accelerator radiation therapy. Methods The dosimeter was used to measure the dose of the medical linear accelerator in the GT direction and the left and right directions at different distances from the therapeutic field. The dose of the linear accelerator at different distances from the isocenter at different fields was measured. The dose distribution of low-dose radiation field is compared with that of the low-dose radiation field in different fields of accelerator. Measurement data for statistical analysis. Results In the field of 10 cm × 10 cm, the dose of scattered radiation in the direction of GT was not significantly different from that in the lateral direction at a distance of 70 cm, which was relatively uniform over 70 cm. The dose of low dose radiation field The field dose increases with the increase of the number of MU in the accelerator field; the dose distribution of accelerator scatter lines of the same type produced by the same manufacturer is basically the same. Conclusion The radiation dose distribution of low-dose scattered radiation in radiotherapy patients is relatively uniform in the field of radiotherapy and increases with the increase of the radiofrequency and the increase of the number of MU in the radiotherapy. In patients undergoing radical radiotherapy, In addition to the penetrating site, the torso is in a relatively uniform field of scattered radiation, and in particular the dose to young patients needs to be assessed.