Quantitative evaluation of susceptibility and shielding effects of nitinol, platinum, cobalt‐alloy, and stainless steel stents

Abstract

The purpose of this study is to quantitatively estimate the shielding and susceptibility effects of commonly used metallic stents on MR signal. Two experiments were performed using a 3D gradient echo sequence with short TE to image a stent phantom: 1) short TR and high flip angle (contrast enhanced MRA parameters), and 2) long TR (TR ӷ T 1 ) and low flip angle. The factor characterizing susceptibility effects was estimated from the signal phase of the first experiment, and then the factor characterizing the shielding effects was derived from the second experiment. Susceptibility induced signal loss was negligible (<1%) for nonstainless-steel (nitinol, platinum, and cobalt-alloy) stents and totally destructive (100%) for the stainless steel stent. Signal loss due to RF shielding was 31-62% for nitinol stents, 14 -50% for platinum stents, 50 -77% for the cobalt-alloy stents (undetermined for the stainless steel stent), varied with stent orientation, diameter, and wall geometry. In summary, stents made of nitinol, platinum, and cobalt-

Non-Contrast-Enhanced Silent Scan MR Angiography of Intracranial Anterior Circulation Aneurysms Treated with a Low-Profile Visualized Intraluminal Support Device

“…Because 3D TOF-MRA uses the inflow effect to visualize blood flow signal, a higher flip angle is needed to increase the signal intensity 8,24,25 ; however, in areas of slow or turbulent flow, the saturation effect caused by a high flip angle decreases the signal intensity. Therefore, visualization of the neck remnant is difficult, even if the higher flip angle increases the signal intensity in the stent.…”

Carotid Artery Stents: In Vitro Comparison of Different Stent Designs and Sizes Using CT Angiography and Contrast-Enhanced MR Angiography at 1.5T and 3T

“…A scaled excitation angle model describing the behavior of the signal intensity inside the implants as a function of the applied nominal excitation angle was introduced. In the following time, Wang et al 13 performed a quantitative evaluation of susceptibility and radio-frequency artifacts of different stents.…”

“…Stent material generally influences artifacts on MR imaging. Wang et al 13 quantitatively estimated susceptibility and radio-frequency artifacts at 1.5T and found susceptibility artifacts negligible (Ͻ1%) for non-stainless steel (nitinol, platinum, cobalt alloy) stents and totally destructive (100%) for the stainless steel stent. Signal-intensity loss due to radio-frequency artifacts was 31%-62% for nitinol stents, 14%-50% for platinum stents, 50%-77% for the cobalt alloy stents, and undetermined for the stainless steel stents.…”

MRI Virtual Biopsies: Analysis of an Explanted Endovascular Device and Perspectives for the Future

“…Examination of the viscoelastic properties of soft tissues is also possible. Metal induced artefacts can be neutralized to permit the observation of the wires or the stents [49,50]. However, it is still premature to comment on corrosion in early stages of development.…”