三维适形放射治疗挡铅射野质量保证的方法探讨

Quality assurance of lead block field in 3D-CRT

目的 :探讨Matri XX 2D矩阵电离室和X线模拟定位机应用于挡铅射野质量保证的方法及可靠性。方法 :用Matri XX 2D矩阵电离室测得挡铅射野的形状和大小,应用Matlab编程绘制出治疗计划系统(treatment plan system,TPS)中相对应的射野的形状和大小;利用X线模拟定位机拍摄出射野挡铅的验证片并通过计算机上的RT PACS获取保存,对尺寸较大的射野,使用Photoshop图像处理软件合成出包含挡铅射野全部信息的验证片;从TPS调出相对应的包含挡铅射野信息的数字重建影像(digital reconstruction radiography,DRR)。分别比较2对图片包含的射野信息。结果:对60个所测挡铅射野和计划射野进行比较,发现2种射野的形状总体上相符,3种方式的误差分别为(1.71±0.84)、(2.32±0.31)和(2.89±0.47)mm。结论 :利用Matri XX 2D矩阵电离室和X线模拟定位机进行挡铅射野质量保证,简单易行、快速有效,能够满足放疗质控中对射野挡铅的要求。

Objective To investigate the method and feasibility for applying 2D ionization chamber array Matri XX and Xray simulator to quality assurance of lead block field in 3D-CRT. Methods The shape and size were measured for the lead block field with 2D ionization chamber array Matri XX, and determined for treat plan system（TPS） with Matlab. RT PACS obtained and saved the portal images of the field produced by X-ray simulator, and Photoshop software was used to generate the portal images with all information of the lead block field in case of a field with large size. The digital reconstruction radiography（DRR） images with the information on lead block field were extracted from TRS, and then the two sets of images were compared for the information on lead block field. Results The comparison between 60 pairs of lead block fields and planned fields showed that the shapes of the fields accorded with each other and the errors due to the three ways were（1.71±0.84）,（2.32±0.31） and（2.89±0.47） mm respectively. Conclusion 2D ionization chamber array Matri XX and X-ray simulator can realize the quality assurance of lead block field in 3D-CRT easily and effectively.