Enhanced performance of a single-sided MPI scanner with a hybrid surface-volume excitation coil

<i>Objective.</i>Magnetic particle imaging (MPI) is a tracer-based imaging modality featuring high sensitivity and no ionizing radiation, offering strong potential for cancer detection and vascular imaging. However, clinical translation remains challenging due to the difficulty of scaling closed-bore MPI scanners. Single-sided MPI scanners offer a promising alternative by placing all hardware on one side of the subject, enabling open access and compatibility with larger anatomies. However, they suffer from magnetic field inhomogeneity and reduced sensitivity. In this work, we demonstrate a next-generation single-sided MPI scanner with targeted hardware and software upgrades to address these limitations.<i>Approach.</i>Enhancements to our single-sided field-free line (FFL) MPI scanner include a new hybrid surface-volume excitation coil that generates a stronger, more homogeneous excitation field, enabling improved sensitivity across larger imaging regions and a third selection coil. Additionally, a new FFL trajectory correction algorithm was implemented to achieve linear spatial encoding. Scanner performance was evaluated through phantom studies assessing sensitivity, spatial resolution, FFL trajectory linearization, and imaging field of view (FOV).<i>Main results.</i>Superparamagnetic iron oxide nanoparticle dilution studies demonstrated a detection threshold of 2.0 <i>µ</i>g of iron. Spatial resolution was evaluated using a two-rod phantom with 1 mm diameter rods spaced 4 mm apart, which were clearly resolved. The flat FFL control algorithm enabled linearized spatial encoding, confirmed through multi-plane imaging of a triple-rod phantom. Imaging of an anatomical mouse phantom and a spiral phantom is demonstrated across the entire 8 cm FOV, a twofold increase in FOV.<i>Significance.</i>The demonstrated imaging capabilities meet or exceed those of other human-focused MPI scanners, representing a substantial advance for single-sided scanner design. The scanner's performance and accessibility suggest suitability for clinical applications such as breast imaging and near-surface tumor detection.