Note: inproceedings

Abstract: Background: Magnetic Particle Imaging (MPI) is a quantitative imaging modality that resolves super-paramagnetic iron oxide particles (SPIO) with non-linear magnetization by means of static and oscillating magnetic fields. In addition, MPI provides a high temporal resolution, a fully 3D spatial resolution and a high sensitivity for resolving the distribution of SPIOs1,2. With these characteristics MPI has been successfully used for localizing and quantifying SPIO labeled cells in mice over long periods3. Further, multi-spectral MPI has been deployed for cardio-vascular interventions where blood pool tracers can be discriminated from coated instruments4. Usually the SPIOs are available in a fluid form. But coating instruments with liquid SPIOs can be challenging since the particles have to be fixated to the solid material of the instruments. Furthermore as the nanoparticles are imobilized within the PLA, the magnetic relaxation mechanisms are only given by the Neel rotation while the brownian rotation motion is inhibited. Purpose: The purpose of this study is to investigate long-term stable imobilized MPI sensitive nanoparticles embedded within 3D printable and easy to process PLA suitable for instrument coating and multi-spectral MPI imaging. Methods: We embedded imobilized Co particles d= 12nm inside a synthetic polymere structure of polylactic acid (PLA) and coated the tip of 4 catheters of type GLIDECATH Cobra 3 (C3) Fr. 5 0.97mm with different masses of Co of 0.13mg, 0.18mg, 0.34mg and 0.45mg. The catheters were simply coated by dipping them into the melt of CoPLA. As liquid tracer perimag (micromod) in concentration c=2.5mmol/L was filled inside a straight vessel phantom with inner diameter of 2.5mm and the coated catheters were placed inside the vessel phantom. During the real-time measurements with the Bruker Preclinical MPI scanner the catheters were pulled back manually. Results: The tip of catheter 4 (red) with the highest Co mass of 0.45mg was clearly separable from the surrounding perimag (green) and the manual pullback movement as seen in Fig. 1 can be identified in the temporal highly resolved images. The tips of catheters 1-3 were also discernable within the solution of perimag but the contrast was weaker linear corresponding to their lower mass. The measurements were repeated after three months and they show no differences in signal strength and separability. Discussion & Conclusion: The instrumentation coating with CoPLA has shown to be a long-term stable, easy to apply and allows for multi-spectral MPI. It was clearly separable with high contrast from the liquid used blood pool tracer and could be identified in real-time measurements. The use of CoPLA as a embeddable tracer material is not limited to instruments and could be build inside all desirable forms such as fiducials due to its ability to be 3D printable.