非晶硅电子射野影像装置的性能研究

使用DVS(Dosimetric verifying system)软件实现对非晶硅平板探测器的影像采集,通过分析不同辐照条件下得到的射野影像的像素值,研究非晶硅电子射野影像装置(Amorphous silicon electronic portal Imagingdevice,a-Si EPID)的辐射稳定性、剂量响应线性、照射野大小的散射影响以及不同帧时间、不同电容大小等参数设置对EPID读出信号值的影响。结果显示EPID在短期内显示出极好的稳定性,伪影增加了EPID的响应信号,减少两次照射的间隔时间或者增加两次照射剂量比例可使伪影变得更加明显。a-Si EPID具有良好的剂量线性关系,随着射野的增加散射因子也随着增加。因此只要经过适当的散射修正和剂量刻度,EPID可以作为剂量仪用来显示二维剂量分布。

Study on dose-response characteristics with amorphous silicon electronic portal imaging device

The object of this study is to investigate the dose-response characteristics of an amorphous silicon electronic portal imaging device （a-Si EPID）. An in-housing developed DVS（Dosimetric verifying system） software was used to analysis the portal image captured in different conditions, and the relationship of pixel value with dose, field size, dose rate, readout signal variation in different binning mode, gain mode and integration time setting was investigated. The EPID showed an excellent temporal stability on short time .Ghosting effects could increase the sensitivity of the EPID and became more pronounced with decrement of time intervals between two exposures as well as with increment of dose though the EPID response is linear with dose. However, it will be ideal for dosimetry application if some corrections for scatter could be made.