Reinhardt Julia, Nguyen-Trong Thien-Hoa, Hähnel Stefan, Bellemann Matthias E, Heiland Sabine
Sektion Experimentelle Radiologie, Neurologische Universitätsklinik Heidelberg, Im Neuenheimer Feld 400, D-69120 Heidelberg, Germany.
Z Med Phys. 2009;19(4):278-87. doi: 10.1016/j.zemedi.2009.06.002. Epub 2009 Jun 25.
The aim of this study was to qualitatively and quantitatively study MR artifacts of various stents on the basis of in vitro experiments. We were particularly interested whether sequence type and orientation of the stent with respect to the static magnetic field influences the artifact.
We examined 18 stents of different material (nitinol, stainless steel, cobalt alloy), different design of the stent meshes (AccuLink, OmniLink, DynaLink, Xact, Protoge, Wallstent Monorail), different diameter (5-10mm) and different length (18-58 mm) with a turbo spin echo (TSE), a 2D-fast low angle shot (FLASH) and a 3D-FLASH sequence. The MR images were examined qualitatively with respect to possible artifacts. Furthermore we examined the MR data quantitatively: The contrast-noise-ratio (CNR) was determined both within the stent and outside (within the tube); based on these values we calculated the transparency factor P, furthermore we calculated the apparent vascular lumen within the tube and within the stent.
The stents made of stainless steel and cobalt alloy displayed severe susceptibility artifacts. Therefore the vessel lumen within the stent could not be assessed. The nitinol stents showed different artifact patterns: The AccuLink and DynaLink stents showed less artifacts compared to the Xact and Protoge stents. Besides the susceptibility artifacts we found artifacts due to RF shielding by the stent mesh, particularly in TSE sequences.
A MR control of patients after stenting is possible and may yield diagnostic information when using the AccuLink or DynaLink stents. However, it is important to make sure that the stent is MR safe for the field strength used for the examination.
本研究旨在基于体外实验对各种支架的磁共振（MR）伪影进行定性和定量研究。我们特别关注序列类型以及支架相对于静磁场的方向是否会影响伪影。
我们使用涡轮自旋回波（TSE）、二维快速低角度激发（FLASH）和三维FLASH序列，对18个不同材料（镍钛合金、不锈钢、钴合金）、不同支架网眼设计（AccuLink、OmniLink、DynaLink、Xact、Protoge、Wallstent Monorail）、不同直径（5 - 10毫米）和不同长度（18 - 58毫米）的支架进行了检查。对MR图像的可能伪影进行了定性检查。此外，我们还对MR数据进行了定量检查：在支架内部和外部（管腔内）测定对比噪声比（CNR）；基于这些值计算透明度因子P，此外还计算了管腔内和支架内的表观血管腔。
由不锈钢和钴合金制成的支架显示出严重的磁化率伪影。因此，无法评估支架内的血管腔。镍钛合金支架呈现出不同的伪影模式：与Xact和Protoge支架相比，AccuLink和DynaLink支架显示出的伪影较少。除了磁化率伪影外，我们还发现了由于支架网眼的射频屏蔽导致的伪影，特别是在TSE序列中。
支架置入术后对患者进行MR检查是可行的，使用AccuLink或DynaLink支架时可能会产生诊断信息。然而，重要的是要确保支架对于检查所使用的场强是MR安全的。
