Experimental Validation of an Assembly of Optimized Curved Rectangular Coils for the Use in Dynamic Field Free Line Magnetic Particle Imaging

Sequences for real-time magnetic particle imaging

Magnetic Particle Imaging (MPI) is a new imaging modality with the potential to be a new medical tool for angiographic diagnostics. It is capable of visualizing the spatial distribution of super-paramagnetic nanoparticles in high temporal and spatial resolution. Furthermore, the new spatial encoding scheme of a field free line (FFL) promises a ten-fold higher sensitivity. So far, all know imaging devices featuring this new technique feature slow data acquisition and thus, are far away from real-time imaging capability. An actual real-time approach requires a complex field generator and an application of currents with very precise amplitude and phase. Here, we present the first implementation and calibration of a dynamic FFL field sequence enabling the acquisition of 50 MPI images per second in a mouse sized scanner.

Electronic field free line rotation and relaxation deconvolution in magnetic particle imaging

It has been shown that magnetic particle imaging (MPI), an imaging method suggested in 2005, is capable of measuring the spatial distribution of magnetic nanoparticles. Since the particles can be administered as biocompatible suspensions, this method promises to perform well as a tracer-based medical imaging technique. It is capable of generating real-time images, which will be useful in interventional procedures, without utilizing any harmful radiation. To obtain a signal from the administered superparamagnetic iron oxide (SPIO) particles, a sinusoidal changing external homogeneous magnetic field is applied. To achieve spatial encoding, a gradient field is superimposed. Conventional MPI works with a spatial encoding field that features a field free point (FFP). To increase sensitivity, an improved spatial encoding field, featuring a field free line (FFL) can be used. Previous FFL scanners, featuring a 1-D excitation, could demonstrate the feasibility of the FFL-based MPI imaging process. In this work, an FFL-based MPI scanner is presented that features a 2-D excitation field and, for the first time, an electronic rotation of the spatial encoding field. Furthermore, the role of relaxation effects in MPI is starting to move to the center of interest. Nevertheless, no reconstruction schemes presented thus far include a dynamical particle model for image reconstruction. A first application of a model that accounts for relaxation effects in the reconstruction of MPI images is presented here in the form of a simplified, but well performing strategy for signal deconvolution. The results demonstrate the high impact of relaxation deconvolution on the MPI imaging process.