Design, Characterization and Validation of a Single-Sided Field Free Line Scanner for Magnetic Particle Imaging

Abstract

Magnetic particle imaging (MPI) is an emerging tracer based imaging modality capable of detecting superparamagnetic iron oxide (SPIO) nanoparticles with high sensitivity, positive contrast, and without ionizing radiation. These properties make MPI promising for a wide range of biomedical applications, including cancer detection, cell tracking, vascular imaging, and image guided interventions. Preclinically, MPI has demonstrated strong performance, but translation to human scale imaging has remained limited by hardware constraints. Traditional closed bore MPI scanners are not scalable to full human imaging, as the magnetic field strengths required over such volumes demand infeasible power consumption. As a result, hardware development remains an active area of research in MPI, with many groups exploring alternative scanner designs targeted to specific anatomies or employing non conventional geometries. One promising alternative is the single-sided scanner geometry. Single-sided geometries confine all hardware to one side of the imaging subject, enabling open access and accommodating anatomies that cannot be imaged using traditional closed bore designs. However, this topology also presents inherent challenges, most notably inhomogeneous magnetic fields which complicate imaging and limit penetration depth. Additionally, scanners of this topology have traditionally suffered from insufficient sensitivity, restricting them from biological applications where microgram sensitivity is required, such as in-vivo applications. This dissertation presents the design, development, characterization, and validation of a single-sided field free line (FFL) MPI scanner, with a future goal of translation to breast imaging applications. The system addresses challenges traditionally associated with single-sided MPI through multiple design choices, including the use of an FFL for spatial encoding, which provides increased sensitivity. Demonstrated in this work are a theoretical analysis, numerical simulation, and experimental validation of the scanner. Imaging studies using a variety of phantoms establish technical performance and demonstrate suitability for anatomical imaging. In addition, ex vivo imaging of labeled cancer cells demonstrates biologically relevant detection sensitivity, and preliminary in vivo imaging studies in mice further support the translational potential of this approach. Together, these results advance single-sided MPI as a viable imaging topology and outline a potential pathway for extending MPI toward clinical applications.