Implementation and imaging with a versatile 180 mm magnetic-particle-imaging field-generator

Magnetic Particle Imaging (MPI) is a non-invasive imaging technique based on the detection of the non-linear magnetization curve of magnetic nanoparticles. The spatial encoding of the particle-distribution measurement relies on the combination of an alternating magnetic field, the excitation field, and a constant or slowly changing field, the selection field. The homogeneous excitation field undergoes a harmonic distortion caused by the particles. This distortion can be assigned to a certain location within the measurement field by utilizing the selection field. MPI scanners presented so far use coil designs that lead to selection fields with a field free point or a field free line and have a bore diameter between 30 mm and 120 mm. A recently published system has an elliptical bore with 190 mm width in the narrower dimension. Since the invention of MPI, the bore diameter of MPI systems has not changed significantly. Here, we show the entire process of the design, implementation, and operation of an MPI system that offers a bore diameter of 180 mm. It includes the hardware which enables the generation of a selection field with a field free point and one with a field free line, which accounts for the versatility of the scanner. It enables the preclinical investigation of laboratory animals with the corresponding dimensions by imaging a field of view of 40 mm × 40 mm. This study is an incremental step towards the design and operation of larger MPI scanners to finally reach clinical applications.