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.