Lambert Jack W, Edic Peter M, FitzGerald Paul F, Torres Andrew S, Yeh Benjamin M
University of California , Department of Radiology & Biomedical Imaging, 505 Parnassus Avenue, San Francisco, California 94143, United States.
GE Global Research , 1 Research Circle, Niskayuna, New York 12309, United States.
J Med Imaging (Bellingham). 2015 Jul;2(3):033503. doi: 10.1117/1.JMI.2.3.033503. Epub 2015 Sep 21.
Metal artifacts have been a problem associated with computed tomography (CT) since its introduction. Recent techniques to mitigate this problem have included utilization of high-energy (keV) virtual monochromatic spectral (VMS) images, produced via dual-energy CT (DECT). A problem with these high-keV images is that contrast enhancement provided by all commercially available contrast media is severely reduced. Contrast agents based on higher atomic number elements can maintain contrast at the higher energy levels where artifacts are reduced. This study evaluated three such candidate elements: bismuth, tantalum, and tungsten, as well as two conventional contrast elements: iodine and barium. A water-based phantom with vials containing these five elements in solution, as well as different artifact-producing metal structures, was scanned with a DECT scanner capable of rapid operating voltage switching. In the VMS datasets, substantial reductions in the contrast were observed for iodine and barium, which suffered from contrast reductions of 97% and 91%, respectively, at 140 versus 40 keV. In comparison under the same conditions, the candidate agents demonstrated contrast enhancement reductions of only 20%, 29%, and 32% for tungsten, tantalum, and bismuth, respectively. At 140 versus 40 keV, metal artifact severity was reduced by 57% to 85% depending on the phantom configuration.
自计算机断层扫描(CT)问世以来,金属伪影一直是与之相关的一个问题。近期用于减轻这一问题的技术包括利用通过双能CT(DECT)生成的高能(keV)虚拟单色光谱(VMS)图像。这些高能keV图像存在的一个问题是,所有市售造影剂提供的对比度增强会大幅降低。基于原子序数较高元素的造影剂在可减少伪影的较高能量水平下能够维持对比度。本研究评估了三种此类候选元素:铋、钽和钨,以及两种传统造影元素:碘和钡。使用一台能够快速切换工作电压的DECT扫描仪对一个基于水的体模进行扫描,该体模中的小瓶装有这五种元素的溶液以及不同的产生伪影的金属结构。在VMS数据集中,观察到碘和钡的对比度大幅降低,在140 keV与40 keV相比时,碘和钡的对比度分别降低了97%和91%。相比之下,在相同条件下,候选造影剂在140 keV与40 keV相比时,钨、钽和铋的对比度增强降低分别仅为20%、29%和32%。根据体模配置,在140 keV与40 keV相比时,金属伪影严重程度降低了57%至85%。