Bare-Metal Stent Tracking with Magnetic Particle Imaging

Abstract

Franz Wegner,1 Thomas Friedrich,2 Maximilian Wattenberg,2 Justin Ackers,2 Malte Maria Sieren,1,3 Roman Kloeckner,1 Joerg Barkhausen,3 Thorsten M Buzug,2,4 Matthias Graeser,2,4 Anselm von Gladiss5 1Institute for Interventional Radiology, University of Luebeck, Luebeck, Germany; 2Fraunhofer Research Institution for Individualized and Cell-Based Medical Engineering IMTE, Luebeck, Germany; 3Department of Radiology and Nuclear Medicine, University of Luebeck, Luebeck, Germany; 4Institute of Medical Engineering, University of Lubeck, Luebeck, Germany; 5Institute for Computer Science, University of Koblenz, Koblenz, GermanyCorrespondence: Franz Wegner, University of Luebeck, Institute for Interventional Radiology, Ratzeburger Allee 160, Luebeck, 23538, Germany, Tel [phone], Fax [phone], Email [email protected]: 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

Keywords

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