MR-velocity mapping in vascular stents to assess peak systolic velocity. In vitro comparison of various stent designs made of Stainless Steel and Nitinol

Introduction. Peak systolic velocity (PSV) measurements of blood flow inside vascular stents allow reliable detection of in-stent restenosis. The purpose of this in vitro study was to evaluate the feasibility of obtaining PSV measurements inside vascular stents made of Stainless Steel and Nitinol, using a velocity encoded MR technique. Materials/methods: In a flow phantom, stents of Stainless Steel and Nitinol were studied. The phantom was integrated into a closed-tubing circuit driven by a MR dedicated pulsatile flow pump. MR imaging was performed on a 1.5 T system. The PSV in the tube without stent was used as the gold standard to determine the accuracy and the variability (paired t-test and Pittman's test) of the PSV measurements inside the stents. Results: PSV values inside the stents showed percentual difference in mean of -15 to 21% (P < 0.05) at a pump setting of 10 and 20 ml/s. Conclusion: PSV measurements can be accurately obtained inside stents made of Stainless Steel and Nitinol. MR-velocity measurements may be used in patients to non-invasively evaluate stent patency and in-stent re-stenosis.

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