MR evaluation of stent patency - In vitro tests of 22 metallic stents and the possibility of determining their patency by MR angiography

RATIONALE AND OBJECTIVES. To determine the extent to which visualization of intrastent anatomy in stents of different composition and design is possib le by using contrast-enhanced MR angiography. METHODS. Twenty-two MR-compatible stents, most of which had a diameter of 8 mm, were positioned in a phantom filled with aqueous gadolinium solution. Coronal and axial spoiled three-dimensional gradient-echo sequences were pe rformed. Images were acquired with stents positioned at varying angulations to the main magnetic field B-0. Profiles orthogonal to the stent axis allo wed measurement of artifact sizes independent of window width and center. RESULTS. Oriented along B-0, the Cragg, Corvita, Passager, Wallstent, Strec ker, Impag, Perflex, and ZA stents allowed visualization of more than 48% o f the lumen. The Memotherm, Smart, and Jostent SelfX stents showed a promin ent reduction of the inner lumen to below 41%. The lumina of the covered Jo stent, Palmaz, Sinus, and Symphony stents were completely obscured. The Imp ag, Perflex, and Strecker tantalum stents shelved growing artifact sizes an d a lumen reduction of at least 40% with increasing angulation to B-0. CONCLUSIONS. Evaluation of the inner stent lumen by applying contrast-enhan ced, three-dimensional gradient-echo sequences is not possible for the majo rity of stents because of their large artifacts. These depend on the stent type and orientation to B-0. Even stents made of nitinol and cobalt alloys only allow qualitative patency assessment but no quantification of stenosis .