International Journal on Magnetic Particle Imaging (IJMPI)
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A novel MPI blood assay for calculating ultra-short half-lives of magnetic tracers
No full textWe present a magnetic particle imaging (MPI)-based blood assay that can be used to accurately calculate the blood half-life of magnetic nanoparticles (MNPs) without the need of labeling them. Dual-catheterized rats received 2.0 mg Fe of Synomag®-D70, Synomag®-D50, Resovist® and Feraheme® by femoral vein injection. The MPI signal of blood samples drawn from the femoral artery at various time points was then measured. Synomag®-D70 exhibited biexponential clearance with half-lives of 3.2 and 31.2 min, Synomag®-D50 a monoexponential clearance (t1/2=11.4 min), Resovist® a biexponential clearance (t1/2=2.4 and 10.8 min), and Feraheme® a biexponential clearance (t1/2=60.9 and 4.5 min). Our results showed that this MPI assay is a sensitive and specific method for calculating blood half-life of existing MNP formulations and those in the pipeline, with exquisite sensitivity for ultra-short half-lives
Stimuli-responsive hydrogel patches for resolving pH with magnetic particle spectrometry (MPS)
No full textMagnetic particle spectrometry (MPS) enables the characterization of magnetic nanoparticles (MNPs) in terms of their nonlinear magnetic behavior, which also depends on the particles’ hydrodynamic mobility and, consequently, on the local environment. Therefore, MPS can be used to examine particle-matrix interactions. In this work, the pH value of a solution is resolved using MPS. The underlying principle is based on a pH-responsive magnetic hydrogel patch, which exhibits reversible volume alteration in response to a change in the surrounding pH value. This swelling behavior affects the particle-matrix interactions of embedded MNPs, resulting in a modified magnetic signal. A correlation was observed in which the hydrogel swelling increases with rising pH. In MPS measurements, the amplitudes of the spectra were found to correlate with the extent of swelling and, consequently, with the pH value. As a consequence, the measured MPS spectra can be assigned a specific pH value
Experimental Study on Efficient Field Measurement using Ellipsoidal Harmonics
No full textThis work demonstrates the application of ellipsoidal harmonic expansions for magnetic field representation in Magnetic Particle Imaging (MPI) using measured data. While previous studies focused on simulated fields, we validate the method with field data acquired from a selection field generator of an MPI head imaging system using an ellipsoidal t-design. The approach is validated by comparing the harmonic expansion results to dense principal axis measurements, confirming accurate field characterization. This study highlights the potential of ellipsoidal harmonics to improve the speed and accuracy of magnetic field measurements and representation in MPI
Deconvolution of direct reconstructions in 3D
No full textRecently, a direct reconstruction method for multi-dimensional magnetic particle imaging was proposed, which is based on the summation of weighted frequency components of the measured voltage signals with Chebychev polynomials of second kind. The method works fast but leads to reconstructions of the convolved spatial distribution of magnetic nanoaparticles. In a previous workwewere able to showthat using a neural network model to deconvolve these reconstruction leads to high quality images in the two-dimensional case. In this work, we take this approach one step further and demonstrate that this also applies to three-dimensional data. Therefore, in this work, we apply a neural network model on a simulated data set consisting of three-dimensional volumes containing blood vessel like structures. We show that the proposed network produces high quality deconvolution results and outperformsconventional methods on the data set
Magnetic Phase-Change Nanodroplets for Magnetic Particle Imaging and Magnetic Vaporization
No full textPhase-change nanodroplets (PCNs) are high-potent theragnostic agents for efficient and targeted drug delivery. PCNs can be functionalized to accumulate in tumors, and vaporized by external stimuli. Ultrasound (US) is the primary method for PCN vaporization and imaging. However, it has limitations due to wave propagation effects, relatively high vaporization pressure, and low scattering cross section of PCNs in the liquid phase. Here, we report magnetic phase-change nanodroplets (MPCNs) suitable for magnetic particle imaging (MPI) and vaporization with magnetic heating. MPCNs can enable quantitative monitoring of accumulation in the disease site using MPI, and vaporization with targeted magnetic heating, thereby improving the clinical potential of PCNs as a theragnostic agent
Development and Assessment of a 1D-MPS
No full textA novel one-dimensional modular magnetic particle spectrometer (1D-MPS) is herein presented, constructed to address the inherent limitations and stability issues associated with its predecessors.The design permits modifications at the component level, ensuring a flexible as well as adaptable system and features a robust decoupling of receiver and transmitter paths, effective shielding of signal components, and improved mechanical decoupling.The preliminary evaluation of the system shows promising results with regard to stability and reproducibility, indicating its potential to enhance measurement results across a range of applications
Tomographic Imaging of Implanted Tumors in a Breast Phantom with a Single-Sided MPI Scanner
No full textThe conventional closed-bore MPI scanners restrict the imaging volume. A single-sided MPI scanner design allows for an unrestricted imaging volume, uniquely enabling the imaging of objects larger than those accommodated by commercially available MPI scanners. Here, we demonstrate our single-sided scanner\u27s capabilities for potential breast cancer screening by imaging a large anatomical breast phantom
Multi-color MPI for distinguishing two different MNP systems following cellular uptake
No full textTo demonstrate the capability of multi-color magnetic particle imaging (MPI) to distinguish different magnetic nanoparticle (MNP) systems after cellular uptake, we investigated two distinct MNP samples following uptake by THP-1 monocytes. Magnetic particle spectroscopy (MPS) and MPI were employed to characterize the unique magnetic signatures of each MNP-labeled cell sample, allowing for clear differentiation. These findings establish the basis for future applications in tracking specific monocyte subpopulations, thereby enabling detailed investigation of immune cell functions and migration patterns within inflammatory processes
A smart combination: A study on viscosity influences on SMART RHESINS using COMPASS
No full textTo enable reliable quantification of magnetic nanoparticles, new methods to prevent interactions of particles with their physiological environment are necessary. An innovative approach are SMART RHESINs, where conventional nanoparticles are encapsulated in hollow nanospheres. Here, a detailed study on Perimag® based SMART RHESINs has been performed utilizing critical offset magnetic particle spectroscopy (COMPASS) to show that the influence of the surrounding medium, which was varied in viscosity, on the particle system can be suppressed using SMART RHESINs
In search of multifunctional magnetic nanoparticle design with micromagnetic simulations
No full textMagnetic nanoparticles (MNP) serve as imaging tracers, therapeutic heating agents and biosensors in biomedical applications. All the above applications rely upon the particles’ unique relaxation mechanisms, which lead to phase shifts in alternating magnetic fields and dissipation. As MNP have an intrinsic size distribution and their magnetic properties are also size-dependent, search is ongoing for the optimally sized MNP that could potentially serve for all three applications simultaneously. In this work, we present our current results on simulating the influence of core size, mono- and polydisperse size distributions as well as magnetic anisotropy on the performance of MNP for both heating and biosensing using micromagnetic dynamic magnetization simulations