Bartels L W, Smits H F, Bakker C J, Viergever M A
Department of Radiology, Image Sciences Institute, University Medical Center Utrecht, Heidelberglaan, The Netherlands.
J Vasc Interv Radiol. 2001 Mar;12(3):365-71. doi: 10.1016/s1051-0443(07)61918-6.
The purpose of this in vitro study was to examine the various sources of artifacts in magnetic resonance (MR) imaging and angiography of vascular stents.
Five low-artifact stents-Wallstent (cobalt alloy), Memotherm (nitinol), Perflex (stainless steel), Passager (tantalum), and Smart (nitinol)-were imaged in a vascular flow phantom, consisting of a thin-walled cellulose vessel model connected to a pump system. The echo time and the angulation of the stents with respect to the direction of the main magnetic field were varied. Spin echo and gradient echo images as well as three-dimensional MR angiograms were obtained to study the effects of flow, magnetic susceptibility, and radiofrequency-induced eddy currents.
Susceptibility artifacts were restricted to the stents' direct environment and were mildest at short echo times and with the stents aligned with the main magnetic field. Nitinol stents showed less artifacts than steel stents did. Radiofrequency artifacts obscuring the stent lumen and flow-related lumen displacement were seen in all stents. The extent to which these occurred depended on strut geometry and orientation.
For low-artifact stents, the material the stent is made of is not the only important factor in the process of artifact formation. Susceptibility artifacts, radiofrequency eddy currents and flow-related artifacts all contribute to the image distortion, and are dependent on the geometry and orientation of the struts and on the orientation of the stent in the main magnetic field.
本体外研究的目的是检查血管支架磁共振成像（MR）和血管造影中伪影的各种来源。
在一个血管流动模型中对五个低伪影支架进行成像，该模型由一个连接到泵系统的薄壁纤维素血管模型组成。这五个支架分别是Wallstent（钴合金）、Memotherm（镍钛合金）、Perflex（不锈钢）、Passager（钽）和Smart（镍钛合金）。改变回波时间以及支架相对于主磁场方向的角度。获取自旋回波和梯度回波图像以及三维MR血管造影，以研究血流、磁敏感性和射频感应涡流的影响。
磁敏感性伪影局限于支架的直接周围环境，在短回波时间且支架与主磁场对齐时最为轻微。镍钛合金支架显示出的伪影比钢支架少。在所有支架中均可见掩盖支架管腔的射频伪影以及与血流相关的管腔移位。这些情况出现的程度取决于支柱的几何形状和方向。
对于低伪影支架，支架的制造材料并非伪影形成过程中唯一重要因素。磁敏感性伪影、射频涡流和与血流相关的伪影均会导致图像失真，并且取决于支柱的几何形状和方向以及支架在主磁场中的方向。
