International Journal on Magnetic Particle Imaging IJMPI
Vol. 10 No. 1 Suppl 1 (2024): Int J Mag Part Imag

Short Abstracts

Disk Shaped Magnetic Thin-Film Nanoparticles Tailored for Optimal MPI Signal Generation

Main Article Content

Erik M. Mayr (ETH Zürich), Justin Ackers (Fraunhofer Research Institution for Individualized and Cell-Based Medical Engineering IMTE), Alexander Gogos (Laboratory for Particles Biology Interactions, Department Materials Meet Life, Swiss Federal Laboratories for Materials Science and Technology (Empa)), Subas Scheibler (Magnetic and Functional Thin Film Laboratory, Department Materials Meet Life, Swiss Federal Laboratories for Materials Science and Technology (Empa), Matthias Graeser (Fraunhofer Research Institution for Individualized and Cell-Based Medical Engineering IMTE, Lübeck), Michal Krupiński (Institute of Nuclear Physics, Polish Academy of Sciences, Kraków), Inge K. Herrmann (Nanoparticle Systems Engineering Laboratory, Institute of Energy and Process Engineering, Department of Mechanical and Process Engineering, ETH Zürich, Zürich, Switzerland), Hans J. Hug (Magnetic and Functional Thin Film Laboratory, Department Materials Meet Life, Swiss Federal Laboratories for Materials Science and Technology (Empa), Dübendorf, Switzerland)

Abstract


Magnetic Particle Imaging (MPI) generates signals through the nonlinear magnetization response of magnetic nanoparticle tracers to an external magnetic field. The common tracers used so far are superparamagnetic iron oxide (SPIO) nanoparticles. These particles exhibit a modest saturation magnetization and follow a Langevin-type magnetization curve, which restricts their dM/dH response. Consequently, this leads to a limited generation of higher harmonic signals in magnetic field drive oscillations, thereby affecting the sensitivity and spacial resolution achievable in MPI setups.




In our research, we have adopted a top-down approach for nanoparticle fabrication. This process begins with the sputter-deposition of multilayers on a Germanium sacrificial layer, which is evaporated onto a silicon wafer. From these layers, circular nanoscale islands are then patterned. The analysis of the magnetic properties of these islands revealed an M(H) loop characterized by a narrow switching field distribution and coercive fields below 1 mT. To create a nanoparticle suspension, these circular islands were detached from the wafer through the dissolution of the sacrificial layer. The recorded magnetic particle spectra of these disk-shaped magnetic nanoparticles showed a significant enhancement in the amplitudes of the higher harmonics when compared to perimag® particles. This advancement allows for the detection of signals up to the nth harmonic, leading to a marked improvement in MPI performance.


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