International Journal on Magnetic Particle Imaging (IJMPI)
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A Simulation Study for an Open-Sided Hybrid MPI-MRI Scanner
No full textMagnetic particle imaging (MPI) provides background-free images of magnetic nanoparticle distribution. MPI would benefit from an additional imaging technique that reveal the anatomical background information, requiredin many applications. Here, we present a simulation study based on our in-house open-sided prototype MPI system, in which the coils can be utilized interchangeably for MPI and MRI data acquisitions. The system can providea selection field gradient of 0.5 T/m for MPI in field free line topology, and B0 field of up to 50 mT for MRI. We analyze the system-induced deviations on MRI images for different B0 values and pulse sequence parameters
Pulsed rotational drift spectroscopy sequences for magnetorelaxometry
No full textRotational Drift Spectroscopy (RDS) is a novel spectroscopic method for magnetic nanoparticles. It is based on measuring therotational drift of magnetic nanoparticle ensembles in a rotating magnetic field, which is below the magnetic field strength necessary forrotating the magnetic nanoparticles synchronously. Magnetorelaxometry (MRX) measures the decaying magnetization after applying amagnetic pulse, allowing to determine the zero-field relaxation time of magnetic particle systems. It is used, e.g., for general particlecharacterization or bioassay applications. The following work presents pulsed RDS sequences for measuring the zero-field relaxationbehavior of magnetic particles. Measuring the zero-field relaxation using an RDS setup provides the advantage of allowing the combinationof additional measurement sequences for more specific particle characterizations. The pulse sequence can be tailored to the necessaryrelaxation time range of the particle system, allowing to cover a wide range of different relaxation times
Adaptive Permissible Region Strategy for Magnetic Particle Imaging
No full textMagnetic particle imaging (MPI) is a new kind of molecular imaging technique which is designed to locate the superparamagnetic iron oxide (SPIO) with high resolution and sensitivity. The inverse problem of MPI is a challenge problem and many reconstruction methods have been proposed. In this paper, we proposed the adaptive permissible region (APR) strategy to promote the reconstruction efficiency. We apply APR strategy on Kaczmarz method and verify its performance with OpenMPI data set. As a general strategy, APR strategy can obviously reduce the reconstruction time in all conditions, and even promote the reconstruction result with proper parameter
Magnetoviscoelastic models in the context of magnetic particle imaging
No full textSome mathematical models of magnetic particle imaging include the Landau-Lifshitz-Gilbert equation that is known to model the dynamic behavior of the magnetization vector in the micromagnetic theory. Bearing in mind the fluid-structure interaction of the magnetic particles in a viscoelastic environment like blood or tissue, we discuss a modeling approach of the underlying physics that takes a magnetoviscoelastic coupling into account. In particular, we discuss applicability of models for the evolution of magnetoviscoelastic materials consisting of the incompressible Navier-Stokes equations, an evolution equation for the deformation gradient and the Landau-Lifshitz-Gilbert equation. We also consider potential implications of recent work by the authors about two-component magnetoviscoelastic materials for an advanced mathematical modeling of magnetic particles embedded into viscoelastic materials
In vivo therapeutic cell tracking using magnetic particle imaging
No full textWhite blood cells (WBCs) are a key component of our immune system. They play an essential role in surveillance, defense and adaptation against foreign pathogens during an immune response. Immunotherapies and immunomodulatory medications have become indispensable for treating cancer and immune disorders. Hence, imaging the immune response could help medicine diagnose and treat infections, inflammatory diseases like cardiovascular disease, and cancer. Currently, doctors rely on imaging tools like In-111 WBC scans to visualize the immune response. However, these tools destroy CAR-T and CAR-NK cells with radiation before they home to a tumor. A new biomedical imaging tool, Immuno-MPI, could remedy this pitfall and help doctors and researchers optimize immunotherapy for solid tumors. MPI uses no radiation to track cells. Its tracers also have infinite persistence. Here, we compare the effects and sensitivity limits of MPI to In111-WBC scintigraphy
Rapid TAURUS for Real-Time Color MPI A Feasibility Study
No full textRecent developments in color magnetic particle imaging (MPI) provided additional functionalities to MPI, such as distinguishing magnetic nanoparticles (MNPs) by type or by their environmental conditions. In this work, we propose rapid TAURUS (TAU estimation via Recovery of Underlying mirror Symmetry) to achieve relaxation-based real-time color MPI. The method can successfully map the effective relaxation time constants in a relatively wide field-of-view (FOV) at frame rates exceeding 5 frames-per-second (FPS). We present the first simulation results demonstrating that rapid TAURUS is capable of generating high fidelity and high FPS color MPI images in real time
Shift coil assembly for a rotating permanent magnet FFL human-scale fMPI imager
No full textWe present the fabrication and characterization of a shift coil assembly designed for a rotating permanent magnet FFL human fMPI imager. The realized system consists of two sets of inner and outer coils (“racetracks”), each driven by an independent amplifier. Hollow conductors and a highly parallel water-cooling circuit provide heat removal during operation. The measured electrical characteristics of the coils (Rinner = 310 mOhms, Linner = 26 mH, Router = 399 mOhms, Louter =41 mH, M = 22.6 mH) match simulated values well, and field efficiency measurements demonstrate ability to shift a 1.03 T/m FFL over a 20 cm FOV within driving capabilities of the amplifier system (field efficiency = 0.215 mT/A)
Encapsulation in human and murine erythrocytes of the Synomag®-D-PEG-OMe tracer for MPI application
No full textRecently, the potential of red blood cells (RBCs) loaded with superparamagnetic iron oxide (SPIO)-based nanoparticles as new blood-pool tracer material for the Magnetic Particle Imaging (MPI) has been investigated. It was shown that the encapsulation of SPIO-based contrast agents in the RBCs increase the circulation time in blood of these nanomaterials. However, not all iron oxide nanoparticles are eligible to the encapsulation into RBCs, depending on several factors such as dispersant agent nature, nanoparticle size and synthesis protocol. Therefore, we have recently started a program to identify those nanoparticles that can be potentially loaded with our method into RBCs. The goal is to produce biocompatible SPIO-RBCs carriers that can be used as new intravascular magnetic susceptible agents in biomedical applications, such as MRI and MPI. Here, we report the in vitro results obtained by using the Synomag®-D-PEG-OMe nanoparticle suspension (micromod Partikeltechnologie GmbH) with both human and murine red blood cells. MPS analysis showed that human Synomag®-D-PEG-OMe-loaded RBCs produced a signal that is weaker respect to the remarkable signal obtained with ferucarbotran loaded-RBCs prepared at the same condition, but it is to be noted that the encapsulation efficiency of Synomag®-D-PEG-OMe into cells is lower compared to ferucarbotran nanoparticles.
Int. J. Mag. Part. Imag. 8(1), 2022, Article ID: 2209001, DOI: 10.18416/IJMPI.2022.220900
Influence of magnetic nanoparticles interactions on their magnetic particle imaging performance
No full textAbstract: The here presented study investigated the influence of magnetic particle-particle interactions within the MPI tracer MNP on the imaging performance of the tracers. To realize a proper separation and to increase the distances between the individual tracer MNP (which results in reduced particle-particle interactions), the MNP were diluted by non-magnetic SiO2 spacers in the nanometer range. The obtained MNP/SiO2 mixtures were characterized and used to build up measurement phantoms by embedding the mixture into a long-term stable polymer matrix. In MPS and MPI measurements it was found that reduction of the magnetic interactions encompassed by increasing the MNP distances leads for the tested tracer system to a weaker decrease of higher harmonics in the MPS spectra after immobilization of the particles and thereby, a higher spatial MPI resolution can be achieved
Instrument markers for magnetic particle and magnetic resonance imaging
No full textFor MPI, with its huge potential for cardiovascular applications, there is the need to develop dedicated interventional instruments. Especially, for MPI-MRI hybrid imaging approaches the instruments must be both, safe and visible in each modality. The purpose of this study was to manufacture bimodal instrument markers for MPI and MRI. To guarantee sufficient imaging performance in both modalities, the markers are based on two different particle types