International Journal on Magnetic Particle Imaging (IJMPI)
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Magnetic particle imaging of vascular inflammation in abdominal aortic aneurysm in murine model
No full textAbdominal aortic aneurysm (AAAs) is a vascular disease, currently one of the leading causes of death in developed countries. Vascular inflammation plays a crucial role in the disease progression and substantially impacts many determinants in AAAs advancement. Superparamagnetic iron oxide nanoparticles (SPION) have been shown to be suitable agents for molecular targeting of vascular inflammation. The quantitative ability of MPI in mapping of SPION makes MPI a valid tool for monitoring of AAA progression. In this study, we examined the feasibility of MPI for imaging vascular inflammation in AAA in Angiotensin II-infused ApoE-/- mice with MPI suitable SPION, ferucarbotran (Resovist ®). The results were validated by histological analysis and magnetic particle spectroscopy (MPS)
Recent Developments on System Function/Matrix Representation, Hybrid Simulation Techniques, and Magnetic Actuation
No full textThe first issue of the sixth volume of the International Journal on Magnetic Particle Imaging presents four papers focusing on different aspects of the image reconstruction problem in magnetic particle imaging (MPI) and developments in magnetic actuation. The original research articles provide deeper insights into system function/matrix representation in terms of Chebyshev polynomials and they exploit a singular value decomposition (SVD) approach to reduce the size of the imaging problem. Introducing new experimental techniques enable gathering insights in the MPI methodology and magnetic actuation applications benefit from the development and analysis of new tools.
Int. J. Mag. Part. Imag. 6(1), 2020, Article ID: 2010001, DOI: 10.18416/IJMPI.2020.201000
Exploring Parameters of Magnetic Particles in 1D Field Excitation
No full textThis work explores how different parameters, e.g. magnetic anisotropy and core radius, influence the signal/spectrum of magnetic particles in a one-dimensional excitation field. Simulations are performed using a model considering both the mechanical and magnetization dynamics of the particle. The performed simulations show an increase of amplitude at higher harmonics for anisotropy constants within a certain range. This increase is also observed for different magnetic radii. The obtained knowledge can help to improve the performance of magnetic particles in magnetic particle imaging.
Int. J. Mag. Part. Imag. 6(2), 2020, Article ID: 2004001, DOI: 10.18416/IJMPI.2020.200400
Blind Source Separation for Multi-Color MPI
No full textIn magnetic particle imaging (MPI), different magnetic nanoparticles (MNPs) in the same field-of-view can be distinguished via color-MPI techniques. Existing system-function-based techniques require extensive calibration scans, whereas x-space-based approaches require either multiple scans at different drive field parameters, or rely on the underlying mirror symmetry of the adiabatic MPI signal. In this work, we propose a novel blind source separation technique for multi-color MPI, exploiting the distinct signal delays of different MNPs. The proposed technique blindly decomposes the MPI signals from different MNPs, which can then be individually reconstructed and assigned to separate color channels to form a multi-color MPI image.
Int. J. Mag. Part. Imag. 6(2), Suppl. 1, 2020, Article ID: 2009058, DOI: 10.18416/IJMPI.2020.200905
2D Image using 2nd Harmonic Response Improved by Application of System Function
No full textIn general, a third harmonic component of a magnetic response is used for magnetic nanoparticle imaging (MPI). However, when applying a high AC modulated magnetic field to magnetic nano-particles (MNPs), the size of the apparatus become large, and a high power source is required. Thus, we have been investigating an imaging method using a second harmonic with a signal intensity higher than that of the third harmonic. Since the signal of the second harmonic component has positive and negative peaks, signal processing is necessary to represent the position of the MNPs. Therefore, we investigated a method to quantitatively represent the position and the content of magnetic nanoparticles not using differentiation but applying a system function. Results showed that the identification of the amount and the position of MNPs was possible.
Int. J. Mag. Part. Imag. 6(2), Suppl. 1, 2020, Article ID: 2009043, DOI: 10.18416/IJMPI.2020.200904
Reducing displacement artifacts by warping system matrices in efficient joint multi-patch magnetic particle imaging
No full textThe reconstruction of multi-patch magnetic particle imaging data requires a compromise between image quality and calibration time. While optimal image quality is ensured by the joint reconstruction approach, a system matrix needs to be acquired for each patch. One can reuse system matrices by shifting them in space, which decreases the calibration effort but leads to distortions due to field imperfections. In this work, we introduce a method for reducing displacement artifacts in the efficient joint multi-patch reconstruction. Based on the magnetic fields we propose a mapping that warps the central system matrix to capture the spatial displacement of off-center system matrices. In this way, we can maintain the low calibration time while significantly improving the image quality.
Int. J. Mag. Part. Imag. 6(2), Suppl. 1, 2020, Article ID: 2009030, DOI: 10.18416/IJMPI.2020.200903
MPI visualization and inductive heating of hybrid implant fibers
No full textIn this study, we evaluate the hyperthermia efficiency of polypropylene (PP) fibers with incorporated magnetic nanoparticles (MNP), which are used to develop inductive heatable stents in cancer therapy. Further, we investigate their depiction in magnetic particle imaging (MPI). We show that the intrinsic loss power (ILP) value depends on the MNP agglomeration state and their concentration inside the fibers, while the intensity values in the MPI images show a linear response with MNP concentration. We conclude that MNP dynamic magnetic behavior strongly changes with different MNP agglomeration states and magnetic field settings.
Int. J. Mag. Part. Imag. 6(2), Suppl. 1, 2020, Article ID: 2009024, DOI: 10.18416/IJMPI.2020.200902
Magnetic performance of Synomag® nanoparticles in various environments
No full textThis work is an assessment of changes in magnetic properties of magnetic nanoparticles in various biological environments. To mimic variations in biological conditions, we have evaluated magnetic performance of Synomag® nanoparticles in two experiments: the effect of viscosity by varying the ratio of glycerol/water mixture and the effect of immobilization after blocking the Brownian relaxation by freeze-drying (to mimic uptake in macrophages). The magnetic response was measured with the Superparamagnetic quantifier. Synomag® exhibits a slight decrease (7.9%) of magnetic response under increased viscosity from ?1=0.95 to ?6=259.71 mPa.s, and a dramatic magnetic signal drop (78.2%) after freeze-drying. Synomag® nanoparticles are less sensitive to viscosity due to an additional relaxation mechanism of disordered spins within the nanoflowers. However, the magnetic performance has been reduced due to the blocking of Brownian relaxation after immobilization.
Int. J. Mag. Part. Imag. 6(2), Suppl. 1, 2020, Article ID: 2009022, DOI: 10.18416/IJMPI.2020.200902
Development of a microfluidic platform for the synthesis of MPI tracer materials
No full textTo avoid the disadvantages of classical batch-wise coprecipitation in the synthesis of iron oxide nanoparticles we developed a microfluidic synthesis platform with continuous flow mode which enables a faster and more efficient adjustment of relevant parameters like pH-value, temperature and educt concentration. Initial results of the electrostatically stabilized particles demonstrate the high potential for the use as tracer in magnetic particle imaging or contrast agent in magnetic resonance imaging outperforming the efficacy of the current gold-standard Resovist®.
Int. J. Mag. Part. Imag. 6(2), Suppl. 1, 2020, Article ID: 2009007, DOI: 10.18416/IJMPI.2020.200900
Single harmonic based narrow-band magnetic particle imaging
No full textIn this study, we present a narrow-band Magnetic Particle Imaging (MPI) system based on the measurement of the 3f0 harmonic of magnetic nanoparticles. A spot sample is used to measure the point spread function (PSF). The spatial resolution of the system estimated from the full width at half maximum of the PSF is 2 mm and 2.5 mm in z- and x-direction, respectively. Phantom experiments are performed to demonstrate the feasibility of the proposed method for MPI using a single harmonic. In addition, the experimental results indicate that two lines of the MNP sample with a distance of 3 mm can be distinguished in x- and z-directions. It indicates that the measured spatial resolution is better than 2.5 mm, which fits very well with the estimated spatial resolution from the PSF