大孔径CT图像质量保证的自动化方法研究

摘要

目的:对Philips大孔径CT由系统模体自动化扫描的图像质量数据与Catphan 504模体手动扫描的数据进行对比分析,探讨图像质量保证自动化实现的可行性.方法:对2种模体以Philips内置条件扫描,并对Catphan 504模体增加一组标准条件扫描,分析图像的CT值、均匀性、噪声、高分辨率、低分辨率以及层厚等数据之间的差异,并比较时间效率.结果:以内置条件扫描2个模体的CT值为1.53 HU和17.00 HU;均匀性为-0.7 HU和-1.7 HU;噪声为0.61%和0.55%;高分辨率为5.4 lp/cm和6.0 lp/cm;低分辨率(0.3%)为4.6 mm和5.0 mm;层厚(1.5 mm)为1.74mm和1.45mm.标准扫描条件下Catphan 504的CT值为16.30HU,均匀性为-1.3HU,噪声为0.33%,高分辨率为6 lp/cm,低分辨率(1%)为2.0 mm,层厚(9.0 mm)为8.63 mm.除CT值有较大差异外,其他结果均满足厂商验收标准或国家标准.两种模体扫描分析所需时间分别为9min和45min.结论:Philips CT自动扫描分析结果能够满足临床对CT图像质量保证的要求,并极大缩短扫描数据分析所需时间,为临床物理师提供方便快捷的质量控制和质量保证工具.%Objective:To discuss the influence factors and solution of common artifact in the imaging process of multi-slice computed tomography (MSCT), so as to improve the image quality and obtain better quality for image document.Methods: 139 patients once were scanned by using PHILIPS 64-MSCT were enrolled and their documents were analyzed, and these cases included 38 cases with head artifact, 53 cases with chest artifact, 29 cases with abdominal artifact and 19 cases with pelvic artifact. To analyze the morphology and cause of every CT image artifact.Results:In 38 cases with head artifact, 24 cases were caused by hardening of bundle of rays, 1 case was caused by fault of detector, 2 cases were caused by interpolating algorithm, 1 case was caused by motion, 10 cases were caused by metal material. In 53 cases with chest artifact, 8 cases were caused by hardening of bundle of rays, 9 cases were caused by partial volume effect, 9 cases were caused by insufficient photon, 1 case was caused by under-sampling, 3 cases were caused by scattering, 21 cases was caused by motion, 1 case was caused by metal material, and 1 case was caused by data incomplete of projection. In 29 cases with abdomen artifact, 10 cases were caused by partial volume effect, 5 cases were caused by scattering, 4 cases was caused by motion, and 10 cases were caused by metal material. In 19 cases with pelvic artifact, 5 cases were caused by insufficient photon, and 14 cases was caused by metal material.Conclusion: The artifact of MSCT image are related to many factors, the optimizing scan parameters can effectively eliminate, suppress or avoid image artifact, and obtain high quality image.