Bare-Metal Stent Tracking with Magnetic Particle Imaging

Abstract

Purpose

Magnetic particle imaging (MPI) is an emerging medical imaging modality that is on the verge of clinical use. In recent years, cardiovascular applications have shown huge potential like, e.g., intraprocedural imaging guidance of stent placement through MPI. Due to the lack of signal generation, nano-modifications have been necessary to visualize commercial medical instruments until now. In this work, it is investigated if commercial interventional devices can be tracked with MPI without any nano-modification.

Material and Methods

Potential MPI signal generation of nine endovascular metal stents was tested in a commercial MPI scanner. Two of the stents revealed sufficient MPI signal. Because one of the two stents showed relevant heating, the imaging experiments were carried out with a single stent model (Boston Scientific/Wallstent-Uni Endoprothesis, diameter: 16 mm, length: 60 mm). The nitinol stent and its delivery system were investigated in seven different scenarios. Therefore, the samples were placed at 49 defined spatial positions by a robot in a meandering pattern during MPI scans. Image reconstruction was performed, and the mean absolute errors (MAE) between the signals’ centers of mass (COM) and ground truth positions were calculated. The stent material was investigated by magnetic particle spectroscopy (MPS) and vibrating sample magnetometry (VSM). To detect metallic components within the delivery system, nondestructive testing via computed tomography was performed.

Results

The tracking of the stent and its delivery system was possible without any nano-modification. The MAE of the COM were 1.49 mm for the stent mounted on the delivery system, 3.70 mm for the expanded stent and 1.46 mm for the delivery system without the stent. The results of the MPS and VSM measurements indicate that besides material properties eddy currents seem to be responsible for signal generation.

Conclusion

It is possible to image medical instruments with dedicated designs without modifications by means of MPI. This enables a variety of applications without compromising the mechanical and biocompatible properties of the instruments.

Keywords:

• magnetic particle imaging
• instrument tracking
• interventional instruments
• stent
• medical imaging

Acknowledgments

The authors thank Sabine Wende (Boston Scientific) for stent provision.

Disclosure

Prof. Dr. Roman Kloeckner reports personal fees from Astra Zeneca, Boston Scientific, Bristol-Myers Squibb, BTG, EISAI, Guerbet, Ipsen, MSD Sharp & Dohme, Roche, Siemens, and SIRTEX outside the submitted work. The authors report no other conflicts of interest in this work.

Additional information

Funding

This work was supported in part by the Clinician Scientist Program of the University of Luebeck under Grant CS10-2021.