Bare-Metal Stent Tracking with Magnetic Particle Imaging.

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.

[Magnetic particle imaging : From research to the prospect of clinical use]. / "Magnetic particle imaging" : Von der Forschung zur klinischen Perspektive.

BACKGROUND: Magnetic particle imaging offers far-reaching potential with a unique range of applications. OBJECTIVES: Identification of application scenarios with added value for clinical use. METHODS: Overview of previous application scenarios in phantom and small animal models, evaluation of dual-use potential. RESULTS: With its unique application profile, magnetic particle imaging offers a solution for clinical use where common, established imaging techniques reach their limits. As a tracer imaging technique, it is particularly characterized by its high speed, sensitivity and contrast-to-noise ratio. The low magnetic fields and low power consumption allow imaging to be mobile and taken to locations that were previously inaccessible. CONCLUSION: Magnetic particle imaging has seen rapid development in recent years. The applications demonstrated in the small animal model and phantom were able to support the versatility and added value of the method. With the availability of human imaging systems, the technology must face clinical verification studies.