鼻咽癌常规放疗两种射野衔接方式的剂量分布研究

目的：通过拍片方式比较鼻咽癌常规照射中心矢状面共线和完全共线两种衔接方式的剂量分布。方法：剂量胶片置于6cm厚的固体水模中间，射野分别采用中心矢状面共线衔接和完全共线衔接两种方式布野。90°和270°射野γ-设定为7．3cm，各出束200MU拍片，0度颈切野Y＋设定为7．4cm为出柬400MU后再拍片，测量胶片的剂量曲线分布。结果：完全共线衔接方式拍片，中间的剂量跌落区宽度为2~3mm；中心矢状面共线衔接方式拍片，中间剂量跌落区宽度为1~2mm。结论：临床鼻咽癌常规放疗可采用矢状面共线方式衔接，并适当重叠照射。

A study of the dose distribution of conventional radiation therapy for NPC with two different ways of abutting fields

Objective： To compare the dose distribution between two different ways of abutting fields in conventional radiation therapy for NPC. Methods： Dose-film was placed in the center of 6 cm-thick phantom, abutting fields were designed in two ways： shared line at central-sagittal-plane and shared line completely. The Y- of the 90° field and 270° field were 7.3 cm, the film was exposed to 200 MU for each field, The Y＋ of the 0° field was 7.4 cm, the film was exposed to 400 MU. Then, the dose distribution was measured. Results： There was 2-3 mm width of low dose region when shared line completely, and 1 ~2 mm when shared line at central-sagittal-plane. Conclusion： The way of abutted the fields with shared line at central-sagittal-plane can be adopted for conventional radiation therapy for NPC with appropriate overlap.