摘要目的：探讨利用二维电离室矩阵进行 VMAT 患者透射剂量实时验证的临床价值。方法将二维电离室矩阵面板粘贴固定在加速器 EPID 探测面板上，源到 EPID 探测面板距离为140 cm。电离室矩阵面板上加8 mm 的 RW3固体水以提高信躁比。选取食管癌、前列腺癌、肝癌患者计划，在圆柱形 Cheese 模体上照射测量5次，研究患者计划在模体中剂量验证的可行性与准确性。患者每次治疗时进行实时测量，第1次测量结果作为参考剂量，利用γ分析比较分次间剂量误差。结果采用3％3 mm 标准，Cheese 模体 VMAT 计划的γ通过率为98％左右，食管癌、前列腺癌和肝癌患者实时照射γ通过率分别约为92％、92％和94％。整个治疗过程中各分次的γ通过率都在90％以上。结论二维电离室矩阵可以进行患者 VMAT 过程中患者透射剂量的实时监测，有利于提高患者治疗准确性。

abstractsObjective To study the real?time dose verification with 2D array ion chamber array in volumetric modulated arc therapy ( VMAT) with a 2D array ion chamber array. Methods The 2D ion chamber array was fixed on the panel of electronic portal imaging device (EPID). Source?detector distance (SDD) was 140 cm. 8 mm RW3 solid water was added to the 2D array to improve the signal noise ratio. Patient plans for esophageal, prostate and liver cancers were selected to be delivered on the cylindrical Cheese phantom 5 times in order to validate the reproducibility of doses. Real?time patient transit dose measurements were performed at each fraction. Dose distributions were evaluated using gamma index criteria of 3 mm DTA and 3% dose difference referred to the first time result. Results The gamma index pass rate in the Cheese phantom were about 98%;the gamma index pass rate for esophageal, prostate and liver cancer patient were about 92%, 92% and 94%, respectively. Gamma pass rate for all single fraction were more than 90%. Conclusions The 2D array is capable of monitoring the real time transit doses during VMAT delivery. It is helpful to improve the treatment accuracy.