Suess C, Kalender W A, Coman J M
Institute of Medical Physics, University of Erlangen, Germany.
Med Phys. 1999 Feb;26(2):296-302. doi: 10.1118/1.598516.
Computed tomography (CT) has been established as a major imaging modality in diagnostic radiology. Accordingly, acceptance testing and quality control of CT scanners is of great importance. While most procedures and phantoms for testing are widely accepted, there is still discussion and uncertainty about low-contrast (LC) sensitivity. In our opinion this unsatisfactory situation is caused at least in part by the lack of suitable phantoms for LC resolution measurements. We investigated the commonly used phantoms for LC detectability, the Catphan, and for LC resolution, the ATS phantom. While the Catphan showed stable object contrasts, the ATS phantom's measured contrast exhibited a strong dependence on temperature and x-ray quality. Based on newly developed polyurethane resin materials, we designed and tested a LC resolution phantom with several different contrast steps. The object contrasts showed no dependence on temperature and beam quality. The new LC resolution phantom proved to be very suitable for measuring a scanner's low-contrast sensitivity in the image plane, one of the most important image quality parameters. To assess LC resolution in three dimensions we designed an additional phantom with rows of spherical objects. A first prototype was evaluated in a multicenter study. The setup proved to be very helpful to quantify the in-plane and axial LC sensitivity of spiral CT scan modes.
计算机断层扫描（CT）已成为诊断放射学中的一种主要成像方式。因此，CT扫描仪的验收测试和质量控制非常重要。虽然大多数测试程序和体模已被广泛接受，但关于低对比度（LC）灵敏度仍存在讨论和不确定性。我们认为，这种不尽人意的情况至少部分是由于缺乏用于LC分辨率测量的合适体模所致。我们研究了用于LC可检测性的常用体模（Catphan）以及用于LC分辨率的ATS体模。虽然Catphan显示出稳定的物体对比度，但ATS体模测量的对比度对温度和X射线质量有很强的依赖性。基于新开发的聚氨酯树脂材料，我们设计并测试了一种具有多个不同对比度步长的LC分辨率体模。物体对比度不依赖于温度和射线束质量。新的LC分辨率体模被证明非常适合测量扫描仪在图像平面中的低对比度灵敏度，这是最重要的图像质量参数之一。为了在三维空间中评估LC分辨率，我们设计了一种带有成排球形物体的附加体模。第一个原型在一项多中心研究中进行了评估。该设置被证明对于量化螺旋CT扫描模式的平面内和轴向LC灵敏度非常有帮助。
