Tracking short-term biodistribution and long-term clearance of SPIO tracers in magnetic particle imaging

Abstract

Magnetic Particle Imaging (MPI) is an emerging tracer-based medical imaging modality that images non-radioactive, kidney-safe superparamagnetic iron oxide (SPIO) tracers. MPI offers quantitative, high-contrast and high-SNR images, so MPI has exceptional promise for applications such as cell tracking, angiography, brain perfusion, cancer detection, traumatic brain injury and pulmonary imaging. In assessing MPI's utility for applications mentioned above, it is important to be able to assess tracer short-term biodistribution as well as long-term clearance from the body. Here, we describe the biodistribution and clearance for two commonly used tracers in MPI: Ferucarbotran (Meito Sangyo Co., Japan) and LS-oo8 (LodeSpin Labs, Seattle, WA). We successfully demonstrate that 3D MPI is able to quantitatively assess short-term biodistribution, as well as long-term tracking and clearance of these tracers in vivo.

Biodistribution, Clearance, and Long‐Term Fate of Clinically Relevant Nanomaterials

“…This is in line with the work of Levy et al, which showed residual characteristic magnetization measured by ferromagnetic resonance and a superconducting quantum interference device after 90 d in mouse liver and spleen, indicating the presence of ferromagnetic nanoparticles . Recently, Keselman et al used magnetic particle imaging (MPI) to study SPIONs over a period of 70 d . The authors found that the SPIONs were cleared out of the blood within hours and the liver and spleen showed SPION activity even after 70 d, as shown in Figure , indicating that SPIONs persist for a long time in the body …”

“…Recently, Keselman et al used magnetic particle imaging (MPI) to study SPIONs over a period of 70 d . The authors found that the SPIONs were cleared out of the blood within hours and the liver and spleen showed SPION activity even after 70 d, as shown in Figure , indicating that SPIONs persist for a long time in the body …”

Magnetic particle imaging for radiation-free, sensitive and high-contrast vascular imaging and cell tracking

“…It targets the liver within minutes 3 . The Krishnan group at University of Washington developed SPIOs with 2-fold better spatial resolution compared to Ferucarbutran and extended the circulation time of MPI SPIOs to 2+ hours in mice and 4+ hours in rats using polyethylene glycol coatings 17,18 . Alternative approaches to increasing MPI tracer circulation time include loading SPIOs into red blood cells 7,19,20 .…”

Seeing SPIOs Directly In Vivo with Magnetic Particle Imaging

“…For groups interested in developing MPI technology, challenges include (a) improving the spatial resolution of MPI, which is determined by SPIO tracer size and composition, applied magnetic fields, and SPIO relaxation times [47, 48]; (b) improving the detection sensitivity in MPI; (c) robust multi-color imaging [49, 50]; (d) theranostic MPI for guidance and real-time feedback on hyperthermia heating [51–53] (e) improving tracer circulation time and image contrast [21, 45, 54] ; (f) optimal combination of MPI with anatomic imaging modalities like CT or MRI for multi-modal imaging; (g) targeting SPIOs with great specificity to pathophysiology including cancer, cardiovascular disease, stroke; and (h) scaling up preclinical MPI hardware to human MPI, while observing FDA and EU biosafety restrictions, including peripheral nerve stimulation (PNS) and tissue heating Specific Absorption Rate (SAR) limits [27, 29] . These areas are the focus of the activities of the MPI interest group.…”