To investigate the dose effect of isocenter difference during IMRT dose verification with the 2D chamber array. The samples collected from 10 patients were respectively designed for IMRT plans, the isocenter of which was independently defined as PO, PX and PY. PO wasfixed on the target center and the other points shifted 8cm from the target center in the orientation of x/y. The PTW729 was used for 2D dose verification in the 3 groups which beams of plans were set to 0°. Theg-analysis passing rates for the whole plan and each beam were gotten using the different standards in the 3 groups, The results showed the mean passing rate ofγ-analysis was highest in the PO group, and the mean passing rate of the whole plan was better than that of each beam. In addition, it became worse with the increase of dose leakage between the leaves in PY group. Therefore, the determination of isocenter has a visible effect for IMRT dose verification of the 2D chamber array, The isocenter of the planning design should be close to the geometric center of target.%探讨静态调强放疗计划设计中射野等中心选择对二维电离室矩阵剂量验证通过率的影响.选10例患者资料,以相同目标约束条件分别设计以靶区中心(PO)、x/y方向各偏离靶中心8 cm(PX/PY)为射野等中心的3组计划,采用PTW729二维电离室矩阵行机架角归零式二维绝对剂量验证,以不同验证条件行计划整体和单野γ分析.发现PO通过率最高,整体高于单野,PY组随窄缝漏射量的增加而变差.表明射野等中心选择直接影响验证通过率,设计中应尽量靠近靶区中心.
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