Stent Tracking by Magnetic Particle Imaging

Abstract

Magnetic Particle Imaging (MPI) is a very promising methodology for periinterventional imaging. Interventional instruments have been considered invisible for MPI so far. Currently, MPI visibility is realized by special marking technologies. These modifications cause changes in the biomechanical characteristics of the instruments. In this work, a bare metal stent without nano-modification was tracked with high accuracy by MPI. To check potential MPI signal generation, nine commercial endovascular stents were tested in an MPI system. Two of the stents revealed sufficient MPI signal. As one of these two stents showed relevant heating, subsequent imaging experiments at different setups were performed with a single stent type (Boston Scientific/Wallstent-Uni Endoprothesis, diameter: 16 mm, length: 60 mm) only. The nitinol stent mounted on the delivery system, the fully expanded stent and solely the delivery system were placed at 49 defined spatial positions in a meandering pattern by a robot during MPI scans. Image reconstruction was performed and the mean absolute errors (MAE) between the signals’ centers of mass (COM) and the ground truth positions were calculated. The results of this work show that the tracking of the stent and its delivery system was feasible without nano-modifications. The MAE of the COM were 1.5 mm (pixel resolution: 2 mm) for the stent mounted on the delivery system, 3.7 mm for the expanded stent and 1.5 mm for the delivery system without the stent. In conclusion, accurate stent tracking without nano-modification is possible by MPI in the case of signal generating metal stents.