Ruth C, Joseph P M
Hospital of the University of Pennsylvania, Department of Radiology, Philadelphia 19104, USA.
Med Phys. 1995 Dec;22(12):1977-82. doi: 10.1118/1.597495.
Lanthanide-based compounds such as Gd-DTPA are currently used as contrast agents in MRI. Recent experiments using CT and transmission radiography show that Gd agents can increase image contrast by up to a factor of 2 relative to more commonly used iodinated agents on an equi-molar basis. It has also been suggested that beam hardening artifacts may be reduced with Gd. This hypothesis was experimentally tested on three different CT scanners using a circular water equivalent phantom with contrast filled tube inserts. It was found that the artifacts were a factor of 1.3-1.8 more pronounced with the iodinated contrast compared with Gd-DTPA. A theoretical model which uses an experimentally derived photon energy spectrum is proposed which relates the strength of beam hardening artifacts to the variance (over the energy spectrum) of the attenuation coefficient of the contrast agent. This allows easy assessment of the relative magnitudes of the artifact for different contrast agents.
基于镧系元素的化合物，如钆喷酸葡胺（Gd-DTPA），目前在磁共振成像（MRI）中用作造影剂。最近使用计算机断层扫描（CT）和透射射线照相术进行的实验表明，在等摩尔基础上，相对于更常用的碘化造影剂，钆造影剂可将图像对比度提高多达2倍。也有人提出，使用钆造影剂可能会减少硬化伪影。该假设在三台不同的CT扫描仪上，使用带有造影剂填充管插入物的圆形水等效体模进行了实验测试。结果发现，与钆喷酸葡胺相比，碘化造影剂产生的伪影明显1.3至1.8倍。提出了一个理论模型，该模型使用实验得出的光子能谱，将硬化伪影的强度与造影剂衰减系数的方差（在能谱范围内）相关联。这使得可以轻松评估不同造影剂伪影的相对大小。
