TaiChi加速器机载千伏级影像质量控制体系研究

Study on the quality control system of on-board image with kV level of TaiChi accelerator

目的:对国产TaiChi加速器机载千伏级(kV)影像系统进行研究,并与美国瓦里安OBI影像系统进行对比,以期全面了解TaiChi加速器机载kV影像系统的性能。方法:使用TOR 18 FG模体、Catphan604模体、CT剂量指数(CTDI)模体及影像多功能模体,对TaiChi加速器kV影像系统图像质量的密度分辨率、空间分辨率、空间线性、图像均匀性、空间层厚重建精度、CT准确度和噪声以及影像配准精度和图像剂量与美国瓦里安OBI影像系统进行比较研究。结果:TaiChi加速器千伏级X射线二维平片(kV-kV)空间分辨率与瓦里安OBI影像系统影像质量相近,密度分辨率优于OBI影像系统;千伏级锥形束CT(kV-CBCT)空间线性和空间分辨率已与瓦里安OBI影像系统无明显差异,图像空间层厚重建精度结果优于瓦里安OBI影像图像质量,TaiChi加速器在高密度物质中CT值准确性较差,其与标准数据最大偏差为8.8%,图像均匀性测试结果逊色于瓦里安OBI影像图像质量,TaiChi加速器噪声测试结果范围23.7%~57.2%;kV-CBCT和kV-kV配准偏差均<0.5 mm;TaiChi加速器不同模式下kV-CBCT和kV-kV最大扫描剂量分别为7.058 mGy和0.042 mGy,皆小于已报道的瓦里安和医科达相对应影像剂量。结论:TaiChi加速器kV影像系统在更低的扫描剂量情况下,其图像质量、配准精度等性能参数达到市场主流设备水平。

Objective:To study the system of on-board image with kV level of TaiChi accelerator and compare it with Varian OBI image system,so as to comprehensively understand the performance of the system of the image with kV of TaiChi accelerator.Methods:TOR 18 FG phantom,Catphan604 phantom,the phantom of computed tomography dose index(CTDI),the multi-function phantom of image were used to perform comparison study for the density resolution,the spatial resolution,the spatial linearity,the image uniformity,the accuracy of the reconstructed spatial layer thickness,the CT accuracy,the noise,the accuracy of image registration as well as the image dose between the image quality of image system with kV of TaiChi accelerator and that of American Varian OBI image system.Results:The spatial resolution of two-dimensional plain film(kV-kV)of kV level of TaiChi accelerator was similar with that of image quality of Varian OBI imaging system,and the density resolution of the former was better than that of OBI imaging system,and the spatial linearity and spatial resolution of kV-cone beam CT(kV-CBCT)of the former were not significantly different with those of Varian OBI image system,and the accuracy of the reconstructed spatial layer thickness of the former was better than that of the image quality of Varian OBI.The accuracy of CT value of TaiChi accelerator in high-density materials was less.The maximum deviation between that and the standard data was 8.8%.The test result of image uniformity of the TaiChi accelerator was less than that of Varian OBI image,and the range of the noise test of TaiChi accelerator was 23.7%-57.2%.The registration deviations both of kV-CBCT and kV-kV were less than 0.5mm.The maximum image doses of kV-CBCT and kV-kV under different modes of TaiChi accelerator respectively were 7.058mGy and 0.042mGy,which were smaller than the reported corresponding image doses of Varian and Elekta.Conclusion:The performance parameters of kV image system of TaiChi accelerator under lower scan dose,such as image quality and registration accuracy,have reached to the level of mainstream devices in the field.