Magnetic particle imaging for artifact-free imaging of intracranial flow diverter stents: A phantom study.

Abstract

Magnetic Particle Imaging (MPI) is a new, background- and radiation-free tomographic imaging method that enables near real-time imaging of superparamagnetic iron-oxide nanoparticles (SPIONs) with high temporal and spatial resolution. This phantom study aims to investigate the potential of MPI for visualization of the stent lumen in intracranial flow diverters (FD). Nitinol FD of different dimensions (outer diameter: 3.5mm, 4.0mm, 5.5mm; total length: 22-40mm) were scanned in vascular phantoms in a custom-built MPI scanner (in-plane resolution: ~ 2mm, field of view: 65mm length, 29mm diameter). Phantoms were filled with diluted (1:50) SPION tracer agent Ferucarbotran (10µmol (Fe)/ml; NaCL). Each phantom was measured in 32 different projections (overall acquisition time per image: 3200ms, 5averages). After image reconstruction from raw data, two radiologists assessed image quality using a 5-point Likert scale. The signal intensity profile was measured using a semi-automatic evaluation tool. MPI visualized the lumen of all FD without relevant differences between the stented vessel phantom and the reference phantom. At 3.5mm image quality was slightly inferior to the larger diameters. The FD themselves neither generated an MPI signal nor did they lead to relevant imaging artifacts. Ratings of both radiologists showed no significant difference, interrater reliability was good (ICC 0.84). A quantitative evaluation of the signal intensity profile did not reveal any significant differences (p>0.05) either. MPI visualizes the lumen of nitinol FD stents in vessel phantoms without relevant stent-induced artifacts.