Evaluation of in‐stent stenosis by magnetic resonance phase‐velocity mapping in nickel‐titanium stents

Abstract

Purpose:To evaluate different grades of in-stent stenosis in a nickel-titanium stent with MRI. Materials and Methods:Magnetic resonance phase velocity mapping (MR-PVM) was used to measure flow velocity through a 9-mm NiTi stent with three different degrees of stenosis in a phantom study. The tested stenotic geometries were 1) axisymmetric 75%, 2) axisymmetric 90%, and 3) asymmetric 50%. The MR-PVM data were subsequently compared with the velocities from computational fluid dynamic (CFD) simulations of identical conditions.Results: Good quantitative agreement in velocity distribution for the 50% and 75% stenoses was observed. The agreement was poor for the 90% stenosis, most likely due to turbulence and the high-velocity gradients found in the small luminal area relative to the pixel resolution in our imaging settings. Conclusion:The accuracy of the MRI velocities inside the stented area renders MRI a modality that may be used to assess moderate to severe in-stent restenosis (ISR) in medium-sized vascular stents in peripheral vessels, such as the iliac, carotid, and femoral arteries. Advances in MR instrumentation may provide sufficient resolution to obtain adequate velocity information from smaller vessels, such as the coronary arteries, and allow MRI to substitute for invasive and expensive catheterization procedures currently in clinical use.

Neurovascular stent artifacts in 3D‐TOF and 3D‐PCMRI: Influence of stent design on flow measurement

“…On the one hand, in vivo investigations considered mainly velocity information measured outside the stent by comparing PCMRI flow rates with control values or by detecting flow modifications during the follow‐up . On the other hand, in vitro experiments showed the possibility to capture directly the flow modifications induced by the stenosis within the stent lumen …”

“…Currently limited to research purposes, various attempts to evaluate the intra‐aneurysmal and parent vessel hemodynamics using phase contrast MRI (PCMRI) have been carried out in the presence of FDSs. The additional velocity information of PCMRI offers the possibility to quantify the flow modifications induced by FDS implantation and assess indirectly the level of potential in‐stent stenosis . However, near‐stent PCMRI velocities are potentially affected by device related artifacts which strongly depend on the stent properties.…”

DPIV Prediction of Flow Induced Platelet Activation—Comparison to Numerical Predictions

“…4 MRI measurements and numerical predictions using the Wilcox k-x turbulence model (the same one used by us) show similar velocity profiles for flow through various stenosis models. Depending on the constriction severity, the difference between numerical and measured velocity ranges from about 4 cm/s to 40 cm/s 13 . The authors noted the presence of recirculation zone present downstream of the constriction.…”

“…A blood analog fluid (a mixture of 36% glycerol and 64% water solution with dynamic viscosity of l = 3.5 mPa s, closely approximating that of blood) was seeded with reflective particles (14 lm, Optimage, Edinborough, UK) and circulated past an optically clear scaled up (5:1) compliant stenosis model ( Fig. 1) 13 which mimics coronary vessel wall properties. The transparent models were illuminated by an Argon-Ion laser (Innova 70) light sheet (1 mm thick) and sequential images were recorded using a 768 Â 480 CCD camera (Pulnix TM-9701).…”

MRI Evaluation of a Stented Abdominal Aorta of a Rabbit

“…and 90% stenosis 28 . The present study adds to our previous results by demonstrating the capability of MRI to assess the lumen of smaller stented arteries such as the coronary both clinically and in vitro.…”