A novel preclinical dual-topology magnetic particle imaging scanner

Abstract

Magnetic Particle Imaging (MPI) is a relatively new biomedical imaging modality that can provide excellent sensitivity, contrast and resolution utilising superparamagnetic iron oxide nanoparticles. In MPI, spatial selectivity is achieved through selection fields created by either a permanent magnets or electromagnets. Selection fields generated by different arrangements of magnets result in different topologies of operation for MPI scanners. Among these scanner topologies, most prominent ones are Field Free Point (FFP) and Field Free Line (FFL) scanners, which differ in their advantages and disadvantages. Most importantly, FFL scanners provide improved sensitivity and rapid imaging, but offer only projection format images. FFP scanners offer 3D volumetric acquisition (and thus flexibility in acquiring an image from only a region or slice of interest), but can suffer from relatively lower sensitivity and longer scan times. In standard MPI scanners, as one topology has to be chosen when building a scanner, advantages of the other topology will be forgone. This thesis proposes a hybrid topology that functions as FFL by default, but can be swapped electronically into an FFP topology with the use of a saddle coil pair. This dual-topology scanner allows projection format images that can be used for rapid 2D projecton imaging or serve the purpose of a localizer, which can then be followed by 3D volumetric imaging of a region of interest. A preclinical hybrid scanner utilising the proposed topology is designed and constructed. Additionally, a novel double tuning mechanism that improves ease of tuning and allows for consistently achieving higher decoupling for gradiometer receive coils is introduced, built, and demonstrated.