Linear magnetic nanoparticle structures as key feature in magnetic particle imaging

Physics in Medicine and Biology, vol. 70

Abstract

Abstract Objective: Magnetic particle imaging (MPI) opens huge possibilities in image-guided therapy. Its effectiveness is strongly influenced by the quality of the magnetic nanoparticles (MNP) used as tracers. Besides MNP optimization following different synthesis routes, MNP assembly into linear structures can significantly enhance their performance in MPI. The present study investigates the influence of linear MNP structures on MPI signal for different MNP types. With regard to theranostic applications the role of linear structures in hybrid stent imaging is explored. Approach: Three MNP types were used to create linear MNP structures. MNP respectively the MNP structures were immobilized in a hydrogel and positioned at various orientations relative to the coordinate system of the MPI. A multi-channel reconstruction approach was applied to assess the orientation-specific signal. The insights gained were used to reconstruct a fibre-based polymer stent with incorporated linear structures. Main results: Different linear structure orientations could be delineated and visualized in multi-colour images. Linear structures orientated parallel to the direction of a magnetic excitation field lead to the highest signal intensities and peak positions of MPI frequency spectra were located near multiples of the frequency of the excitation coil. Image reconstructions of the stent were very sensitive to the orientation of linear structures within the fibres. Significance: This study reveals that the assembly of MNP results in non-linear contributions to the MPI signal. Consequently, the MPI signal intensity is not as usual merely linearly correlated with MNP concentration increasing the complexity in image reconstruction. The findings demonstrate the necessity of accounting for MNP structure orientation in image reconstruction. They also reveal the high potential of MPI to detect different MNP types and structures. Linear structures cause either significant signal reduction or signal increase depending on the angular position of the linear structures relative to the direction of MPI magnetic fields.

Authors 8

1. Max Schoenen Aachen Institute of Applied Medical Engineering Medical Faculty

   RWTH Aachen University

   Affiliation as printed

   Institute of Applied Medical Engineering, Helmholtz Institute, Medical Faculty, RWTH Aachen University, Pauwelsstraße 20, 52074 Aachen, Germany

   Institute of Applied Medical Engineering, Helmholtz Institute, RWTH Aachen University Medical Faculty, Pauwelsstraße 20, Aachen, 52074, GERMANY

2. Lennart Göpfert Aachen Institute of Applied Medical Engineering Medical Faculty

   RWTH Aachen University

   Affiliation as printed

   Institute of Applied Medical Engineering, Helmholtz Institute, Medical Faculty, RWTH Aachen University, Pauwelsstraße 20, 52074 Aachen, Germany

   Institute of Applied Medical Engineering, Helmholtz Institute, RWTH Aachen University Medical Faculty, Pauwelsstraße 20, Aachen, 52074, GERMANY

3. Benedict Bauer Aachen Institut für Textiltechnik

   RWTH Aachen University

   Affiliation as printed

   Institut für Textiltechnik, RWTH Aachen University, Otto-Blumenthal-Str. 1, 52074 Aachen, Germany

   Institut für Textiltechnik, RWTH Aachen, Otto-Blumenthal-Str. 1, Aachen, 52074, GERMANY

4. Caroline Emonts Aachen Institut für Textiltechnik

   RWTH Aachen University

   Affiliation as printed

   Institut für Textiltechnik, RWTH Aachen University, Otto-Blumenthal-Str. 1, 52074 Aachen, Germany

   Institut für Textiltechnik, RWTH Aachen, Institut für Textiltechnik, Aachen, 52074, GERMANY

5. Thomas Gries Aachen Institut für Textiltechnik

   RWTH Aachen University

   Affiliation as printed

   Institut für Textiltechnik, RWTH Aachen University, Otto-Blumenthal-Str. 1, 52074 Aachen, Germany

   Institut für Textiltechnik, RWTH Aachen, Otto-Blumenthal-Str. 1, Aachen, 52074, GERMANY

6. Eva Miriam Buhl Aachen Institute of Pathology, Electron Microscopy Facility Institute of Pathology, Electron Microscopy Facility

   Universitätsklinikum Aachen · RWTH Aachen University

   Affiliation as printed

   Institute of Pathology, Electron Microscopy Facility, RWTH Aachen University Hospital, Pauwelsstraße 30, 52074 Aachen, Germany

   Institute of Pathology, Electron Microscopy Facility, RWTH Aachen University Medical Faculty, Pauwelsstraße 30, Aachen, 52074, GERMANY

7. Thomas Schmitz‐Rode Aachen Institute of Applied Medical Engineering Medical Faculty

   RWTH Aachen University

   Affiliation as printed

   Institute of Applied Medical Engineering, Helmholtz Institute, Medical Faculty, RWTH Aachen University, Pauwelsstraße 20, 52074 Aachen, Germany

   Institute of Applied Medical Engineering, Helmholtz Institute, RWTH Aachen University Medical Faculty, Pauwelsstraße 20, Aachen, 52074, GERMANY

8. Ioana Slabu Aachen Institute of Applied Medical Engineering Medical Faculty

   RWTH Aachen University

   Affiliation as printed

   Institute of Applied Medical Engineering, Helmholtz Institute, Medical Faculty, RWTH Aachen University, Pauwelsstraße 20, 52074 Aachen, Germany

   Institute of Applied Medical Engineering, Helmholtz Institute, RWTH Aachen University Medical Faculty, Pauwelsstraße 20, Aachen, 52074, GERMANY