Simple-to-Fabricate and Water-Stable Instrument Markers for Preclinical Magnetic Particle Imaging and Magnetic Resonance Imaging

Franz Wegner,1,2 Paul Rasmus Bielenberg,1 Thomas Friedrich,2 Eric Aderhold,2 Pascal Stagge,2 Jonas Schumacher,2 Justin Ackers,2 Mandy Ahlborg,2 Annika C Dell,2 Ankit Malhotra,2 Matthias Graeser,2,3 Maria-Josephina Buhné,4 Malte Maria Sieren,1,4 Martin A Koch,5 Julian Haegele,6 Roman Kloeckner,1 Thorsten M Buzug,2,5 Jörg Barkhausen,4 Kerstin Lüdtke-Buzug2,5 1Institute of Interventional Radiology, University Hospital Schleswig-Holstein, Lübeck, Germany; 2Fraunhofer IMTE, Fraunhofer Research Institution for Individualized Medical Technology and Engineering, Lübeck, Germany; 3Department of Metrology, University of Rostock, Rostock, Germany; 4Institute of Radiology and Nuclear Medicine, University Hospital Schleswig-Holstein, Lübeck, Germany; 5Institute of Medical Engineering, University of Lübeck, Lübeck, Germany; 6Zentrum für Radiologie und Nuklearmedizin, Grevenbroich, GermanyCorrespondence: Franz Wegner, University Hospital Schleswig-Holstein, Campus Lübeck, Institute of Interventional Radiology, Ratzeburger Allee 160, Lübeck, 23538, Germany, Email franz.wegner@uksh.dePurpose: Magnetic Particle Imaging (MPI) is a tracer-based imaging modality with high spatial and temporal resolution, very promising for cardiovascular imaging and peri-interventional guidance. However, most interventional instruments are invisible in MPI due to a lack of signal generation. Existing instrument marking approaches do not address water durability, which is essential for maintaining temporal consistency during experiments. This study aims to develop a simple and water-stable marking technique with smooth surfaces for interventional devices for preclinical MPI and MRI research.Material and Methods: Commercial superparamagnetic iron-oxide nanoparticles (SPIONs) were mixed with a transparent varnish and applied to nitinol stents via dip-coating. An impregnation solution was used to seal the markers. The coating was optically evaluated by microscopy. The water-stability of the markers was assessed after 24 hours in water by Magnetic Particle Spectroscopy (MPS) of the surrounding fluid. The imaging performance of the markers was tested in preclinical MPI and MRI systems.Results: Microscopy showed homogeneous SPION distribution and smooth marker surfaces after the sealing. MPS revealed no detectable signal of the water which surrounded the sealed markers, indicating their water-stability. The MPI-scans demonstrated sufficient visualization of individual markers at the stent ends (SNR=11.5). In MRI, susceptibility artefacts of the marked stents were 4.6 times larger compared to unmarked references.Conclusion: The presented technique allows for easy fabrication of instrument markers with commercially available components for preclinical experiments with the magnetic imaging modalities MPI and MRI.Keywords: instrument markers, interventional instruments, stents, nanoparticles