Tomographic Field Free Line Magnetic Particle Imaging With an Open-Sided Scanner Configuration

Abstract

Superparamagnetic iron oxide nanoparticles (SPIONs) have a high potential for use in clinical diagnostic and therapeutic applications. In vivo distribution of SPIONs can be imaged with the Magnetic Particle Imaging (MPI) method, which uses an inhomogeneous magnetic field with a field free region (FFR). The spatial distribution of the SPIONs are obtained by scanning the FFR inside the field of view (FOV) and sensing SPION related magnetic field disturbance. MPI magnets can be configured to generate a field free point (FFP), or a field free line (FFL) to scan the FOV. FFL scanners provide more sensitivity, and are also more suitable for scanning large regions compared to FFP scanners. Interventional procedures will benefit greatly from FFL based open magnet configurations. Here, we present the first open-sided MPI system that can electronically scan the FOV with an FFL to generate tomographic MPI images. Magnetic field measurements show that FFL can be rotated electronically in the horizontal plane and translated in three dimensions to generate 3D MPI images. Using the developed scanner, we obtained 2D images of dot and cylinder phantoms with varying iron concentrations between 11 µg/ml and 770 µg/ml. We used a measurement based system matrix image reconstruction method that minimizes 1-norm and total variation in the images. Furthermore, we present 2D imaging results of two 4 mm-diameter vessel phantoms with 0% and 75% stenosis. The experiments show high quality imaging results with a resolution down to 2.5 mm for a relatively low gradient field of 0.6 T/m. Index Terms-Magnetic particle imaging, field free line, open magnetic particle imaging scanner, tomography, magnetic nanoparticles. I. INTRODUCTION S UPERPARAMAGNETIC iron oxide nanoparticles (SPIONs) have been proposed as biocompatible agents for a wide variety of biomedical applications such as magnetic resonance angiography, perfusion imaging, lymph

Magnetic particle imaging: tracer development and the biomedical applications of a radiation-free, sensitive, and quantitative imaging modality

“…44,233 In terms of instrumentation, advancements in sensitivity have most frequently been from developments in coil design. 37,74,78,79,234,235 Regarding tracer development for enhanced sensitivity, the signal intensity is governed by the physical and inherent magnetic properties of the tracer, as with spatial resolution, but is mostly dependent on the Ms. 16,18,55 Although the detection sensitivity of MPI is strong currently, through significant advancement it has the potential to become comparable with that of exceptionally sensitive nuclear imaging techniques. 234 Given what has been discussed, the development of SPIONs with optimal sensitivity and spatial resolution performance has become a crucial part of MPI research.…”

“…[378][379][380] Despite these obstacles, there has been sustained work on the translation and hardware scale-up. 42,43,79,235,381,382 In the design of a functional MPI brain imager, Mason et al developed simulation studies that demonstrated promising capabilities for human-scale systems. 383 In an alternative approach Graeser et al successfully presented a human-sized MPI hardware set-up, tailored for brain applications, that has low technical requirements for fast and flexible operation in a clinical environment.…”

“…Top et al recently engineered the first open-sided FFL prototype MPI scanner. 79 Along with the ability to electronically scan the FOV to generate tomographic images, this open-sided design permits interaction with the subject for potential real-time interventional procedures. The results from initial 2D imaging experiments have shown that high quality images with comparatively low resolutions of 2.5 mm can be produced using very low gradient levels (0.6 T m −1 ).…”

Concept for using magnetic particle imaging for intraoperative margin analysis in breast-conserving surgery

“…In this process, out-of-slice imaging artifacts must be addressed by either a 3D model-based reconstruction or further encoding along the bore. These approaches have been demonstrated in x-space 36 , 95 or system matrix 96 reconstructions. To assess the degree to which the detected nanoparticles near the surface of the specimen, it is important to have 3D knowledge of the surface location.…”

The Reconstruction of Magnetic Particle Imaging: Current Approaches Based on the System Matrix

“…In 2019, Top analyzed the image quality of different FFL trajectories [ 18 ]. In 2020, Top presented the first open-sided MPI system, which can electronically scan the FOV with an FFL [ 24 ].…”