In vitro stent lumen visualisation of various common and newly developed femoral artery stents using MR angiography at 1.5 and 3 tesla

Positive visualization of MR-compatible nitinol stent using a susceptibility-based imaging technique

Background

MR-compatible metallic stents have been widely used for the treatment of arterial occlusive diseases. However, conventional MR techniques have difficulty in accurately localizing the stent position and access the stent restenosis because of the susceptibility and radiofrequency (RF) shielding artifacts caused by the stent mesh. Previous studies have demonstrated that a susceptibility-based positive contrast MR method exhibits excellent efficacy for visualizing MR compatible metal devices. However, the method had not been evaluated in the visualization of stents and for the assessment of stent restenosis.

Methods

The susceptibility-based positive contrast MR method was used to visualize the nitinol stents and assess the stent restenosis by comparing two typical MR positive contrast techniques, i.e., susceptibility gradient mapping using the original resolution (SUMO) and the gradient echo acquisition for super-paramagnetic particles (GRASP) with positive contrast.

Results

Three sets of experiments were respectively performed to investigate the influence of stent orientation and spatial resolution on the susceptibility-based method, and to demonstrate the feasibility of the susceptibility-based method in evaluating the stent restenosis comparing to the two typical MR positive contrast methods, GRASP and SUMO.

Conclusions

The susceptibility-based method provides better visualization and localization of the stent than SUMO and GRASP and has the capability of assessing the stent restenosis.

In vitro stent assessment by MRI: visibility of lumen and artifacts for 27 modern stents

Purpose:

The purpose of this study was to measure artifacts and visibility of lumen for modern and most commonly used stents in vascular interventions according to a standardized test method of the American Society for Testing and Materials (ASTM).

Materials and methods:

Twenty-four peripheral self-expanding nitinol stents and three stainless steel stents with diameters between 5 and 8 mm and lengths between 30 and 250 mm from seven different manufacturers were compared on a 1.5T and a 3T magnetic resonance (MR) scanner. The visualization of lumen and artifacts was measured according to ASTM F2119 for a turbo spin echo (TSE) [repetition time(TR)/echo time (TE) 500/26 ms] and a gradient echo (GRE) (TR/TE 100/15 ms) sequence. The stents were placed parallel and perpendicular to the radio frequency field (B

Results:

There were large differences in visibility of the lumen for the stent models. The visualization of the lumen varies between 0% and 93% (perpendicular to B

Conclusion:

Reliable stent lumen visualization is possible for Misago, Supera, Tigris, and Viabahn stents, if their axis is perpendicular to B

In vitro comparison of intracranial stent visibility using various concentrations of gadolinium contrast agent under 1.5 T and 3 T MR angiography

Background and purpose

MR angiography (MRA) is an increasingly used evaluation method following intracranial stenting. However, the various artifacts created by the stent limit this technique. The purpose of this study was to investigate the effects of various concentrations of gadolinium contrast agent on the visibility and signal characteristics of two stents using the a contrast enhanced MRA technique.

Material and method

Two intracranial stents (Enterprise and Helistent) were placed in polyvinyl chloride tubes as vascular phantoms. They were filled with six different doses of gadolinium contrast agent (1.0, 2.0, 4.0, 6.0, 8.0, and 10.0 mmol/L dimeglumine gadopentetate, respectively) and imaged using 3 T and 1.5 T MR systems. Relative in-stent signal (RIS) was calculated and artificial luminal narrowing (ALN) was obtained using pixel by pixel analysis.

Result

The Enterprise stent, performed in both 1.5 T and 3 T MR systems, showed mean RIS values much less than those for the Helistent for all different doses of gadolinium solution. Increased gadolinium concentration resulted in a gradual reduction in RIS values in the Enterprise group. Also, ALN in the Enterprise group showed no or little change with various gadolinium doses.

Conclusions

The Enterprise stent demonstrated good luminal visibility regardless of gadolinium concentration. The relative in-stent signals were more predictable in the Enterprise stent with various doses of gadolinium. Therefore, the Enterprise stent has been shown to provide better in-stent visibility compared with the Helistent using various gadolinium doses.