A preclinical arbitrary waveform magnetic particle imaging scanner for multi-frequency imaging

Abstract

Magnetic Particle Imaging (MPI) is a tracer based tomographic imaging modal-ity that images the spatial distribution of the magnetic nanoparticles (MNPs) using their nonlinear magnetization response. MPI is a rapidly growing and safe imaging modality with high temporal and spatial resolution, together with high sensitivity. In MPI, different types of MNPs and the properties of their local environment such as viscosity and temperature can be identified via the relax-ation behavior of the MNPs. The optimal drive field (DF) frequency depends on the application of interest. In addition, the sensitivity of quantitative mapping can benefit from imaging at multiple DF frequencies. However conventional MPI systems utilize an impedance matching circuitry tuned to a specific DF frequency to mitigate the reactive power, which in turn restricts the operation of the MPI systems to that frequency. In this thesis, a preclinical arbitrary waveform (AW) MPI scanner is proposed to enable flexible functionality in a wide range of oper-ating frequencies. The AW MPI scanner features three specialized components:(1) an AW drive coil with a reduced inductance achieved by utilizing Rutherford cable windings to enable wideband imaging in a preclinical-size MPI scanner, (2) a gradiometric receive coil designed to have zero mutual inductance with the AW drive coil to alleviate the effect of the direct feedthrough signal while sensitively receiving the MNP signal, and (3) additional capacitor banks to block DC cur-rent while avoiding distortions in the DF waveform. This thesis also proposes a technique for multi-frequency imaging in a single scan using the developed AW MPI scanner. Experimental imaging results demonstrate that MPI images and relaxation maps can be successfully achieved at multiple DF frequencies using the developed AW MPI scanner and the proposed multi-frequency imaging technique.