Magnetic Particle Imaging: Current Applications in Biomedical Research

Abstract

Magnetic particle imaging (MPI) is a new imaging modality with the potential for high‐resolution imaging while retaining the noninvasive nature of other current modalities such as magnetic resonance imaging (MRI) and positron emission tomography (PET). It is able to track location and quantities of special superparamagnetic iron oxide nanoparticles without tracing any background signal. MPI utilizes the unique, intrinsic aspects of the nanoparticles: how they react in the presence of the magnetic field, and the subsequent turning off of the field. The current group of nanoparticles that are used in MPI are usually commercially available for MRI. Special MPI tracers are in development by many groups that utilize an iron‐oxide core encompassed by various coatings. These tracers would solve the current obstacles by altering the size and material of the nanoparticles to what is required by MPI. In this review, the theory behind and the development of these tracers are discussed. In addition, applications such as cell tracking, oncology imaging, neuroimaging, and vascular imaging, among others, stemming from the implementation of MPI into the standard are discussed.Level of Evidence: 5Technical Efficacy Stage: 3J. Magn. Reson. Imaging 2020;51:1659–1668.

Challenges in the development of nanoparticle‐based imaging agents: Characterization and biology

“…Magnetic particle imaging (MPI) or MRI of SPIO nanoparticle contrast agents, such as Feraheme, have been used extensively for immune cell labeling and tracking. MPI is a translatable molecular imaging technology with simultaneous high‐resolution, high‐sensitivity, and real‐time imaging (Panagiotopoulos et al, 2015; Talebloo, Gudi, Robertson, & Wang, 2020). MPI produces linearly quantitative images of SPIO‐tagged cells, and has been used in regenerative medicine to track stem cells (mesenchymal and neural progenitor cells [NPCs]), and in cancer immune therapy to track T‐cells in order to predict clinical outcomes (Zheng et al, 2015; Zheng et al, 2016).…”

Current Progress and Perspective: Clinical Imaging of Islet Transplantation

“…MPI's linear quantitation arises from the linear signal change with nanoparticle concentration, which occurs independent of tissue depth. We anticipate that MPI will be used in addition to MRI (i.e., MPI does not replace MRI, it simply augments MRI as an extra layer of information, like PET/MRI) and is very promising for clinical applications in the future [54,55].…”

Recent progress of magnetic nanoparticles in biomedical applications: A review

“…In the presence of an external alternating magnetic field, any tracer particle present in the FFP undergoes magnetization process which induces current in a secondary receiver coil. [ 249 ] The sharp zero points at the center of magnetic setup is surrounded by a consistent and strong magnetic field gradient. Hence, all other particles outside the FFP point exhibits different magnetization signal compared to the particles present in the FFP.…”

“…As all other particles are in saturation, this time‐varying magnetization in the FFP point induces a voltage that is received by a detector coil. [ 249,251,252 ] As mentioned earlier, the FFP point is not fixed and is relative to the position of outside magnetic poles and sample position; by varying their relative distance, the FFP is rastered over the sample to obtain the signals for each point in the samples which is later reconstructed to generate a heat map of tracer position. [ 253 ] Figure 18 exhibits the image constructed with FDA approved nanoparticles ferumoxytol and ferucarbotran at different concentrations.…”