International Journal on Magnetic Particle Imaging (IJMPI)
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Depth detection capability of handheld magnetic particle imaging under multiple excitation waveforms
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Configuring magnetoresistive sensor array for head-sized magnetic particle imaging
No full textMagnetoresistive (MR) sensors offer a solution to enable unidirectional detection of sub-pT signal. Magnetic particle imaging (MPI) can benefit from this high sensitivity to challenge its operability under low excitation fields. Here, we built a prototype of brain MPI scanner by using MR sensor array to directly map stray fields of the magnetized magnetic nanoparticles. The array was a 13×13 matrix with 15 mm sensor pitch and installed at 100 mm apart from excitation coil with 200 mm in diameter. We magnetically compensated both the drive field and geomagnetism to position MR sensor at field-free environment. Preliminarily, we were able to detect a 37 mgFe ferrofluid sample at 50 mm apart from the array under field amplitudes up to 100 ?T/?0 at 10 kHz. The resulting noise level appears independent to the applied field, which becomes an advantage to further implement higher drive fields within magnetostimulation safety limits
Comparative study of 3 types of MPIs based on permanent magnet movement and FMMD technology
No full textMagnetic Particle Imaging (MPI) is a relatively new medical imaging technology that can find information about the location of a specific disease using nanomagnetic particles with superparamagnetism. After Gleich and Weizencker published a paper on the basic theory and application of MPI in 2005, many studies have published various techniques for MPI. Our research team has made three types of MPI system so far and obtained the images for mouse-sized samples. The generation of Field Free Line (FFL) is basically based on permanent magnets, and the acquisition and processing of signals is based on FMMD. The first one is to hold the permanent magnet stationary and move the imaging object. The second system is to create FFL by mixing a permanent magnet and an electromagnet. The generated FFL is moved mechanically [2]. The third method uses permanent magnets to create FFL and moves them mechanically. Compared to the electromagnet based MPI system, all three MPI systems above can be manufactured and operated at a very low cost in the power and cooling system. However, this study shows that even if the same FFL generation and signal acquisition principles are used, the development direction of commercialization and large-scale research can be different depending on whether the sample is fixed or moved). Since the issues discussed here can be applied to MPI based on permanent magnets in common, it is considered that this can contribute to the development of MPI
Improving single harmonic MPI performance Using perpendicular magnetization
No full textIn single harmonic magnetic particle imaging (MPI), a reconstructed image can be obtained by deconvolution using the point spread function (PSF) of the 3rd harmonic. However, harmonic signals from superparamagnetic iron oxide nanoparticles (SPIOs) at the edge of the field of view (FOV) cannot be picked up, leading to artifacts in the reconstructed image. We propose an improved single harmonic MPI method using perpendicular magnetization to compensate for harmonic data loss. Experimental results show that the image reconstruction quality is improved using our method
Low-cost standalone magnetic particle spectroscopy device for fast and sensitive immunoassays
No full textThe recent pandemic has shown how important reliable assays are for determining whether someone is infectious. One promising alternative to the established testing methods are immunoassays with magnetic nanoparticle (MNP) markers using magnetic particle spectroscopy (MPS). In this work we present the development of our “immunoMPS” which was especially built at low cost for immunoassays with infectious samples. It is a completely self-contained, mobile device with total costs of only 300€ that could be used in S2+ laboratories. The device delivers high performance on par or exceeding our lab equipment. Thus, we achieved a significantly lower limit of detection (LOD) of 4x10^8 viruses/mL of our magnetic immunoassays (MIAs) for the detection of mimic SARS-CoV-2 which is about one order of magnitude better than previous results in this research topic. In addition, it is possible to further improve the limit by optimizing the experimental setup and using DC fields
Development of Optimized Magnetic Particle Imaging Tracers Utilizing Genetically Engineered Magnetosomes
No full textThe imaging quality of Magnetic Particle Imaging (MPI) is not just limited by the MPI system but also by the quality of available tracers. The tracer quality can be improved by optimizing the shape, core size and shell of the nanoparticles. However, such a defined synthesis is quiet challenging. Biogenic magnetic nanoparticles, so-called magnetosomes, synthesized by magnetotoactic bacteria, might provide a promising alternative. In this study, magnetosomes isolated from different Magnetospirillum gryphiswaldense mutant strains biomineralizing particles with varying core diameters were investigated with regard to their usability as tracers for MPI
Insight COMPASS – the physics behind
No full textCritical Offset Magnetic PArticle SpectroScopy (COMPASS) is a new method that allows to detect slight changes in the mobility of particles in a solution very sensitively. While first applications in detecting biomarkers such as SARS CoV 2 antibodies show very promising results, the full potential of the technique and the underlying physical effects were yet only considered superficially. Here we present the first results of a detailed study of the behavior of the particle signal under variations of relevant system parameters with a focus on particle size, viscosity and temperature of the solution to win more information about the behavior of the effect and find new interesting application possibilities
Realistic vascular 3D printed phantom for real-time bolus tracking in a human-sized MPI scanner
No full textPhantoms of blood vessels are an important part of flow measurements and should behave as realistic as possible compared to human blood vessels. A step-by-step guide is presented on how to obtain realistic 3D models of blood vessels applicable for 3D printing and simulation studies. The resulting 3D models have realistic dimensions, are waterproof and could be used in a human-sized MPI scanner. The 3D printed phantoms with vascular pathologies like aneurysm or stenosis were used in static and real-time bolus tracking measurements
Modular Simulation Framework for Magnetic Particle Imaging
No full textSimulations are of high interest in all areas of scientific research, especially for finding novel approaches or optimizing existing methods. For the young field of Magnetic Particle Imaging (MPI) only few quite specific simulation frameworks exist, which cover the entire process from hardware simulation and signal generation to data reconstruction and final visualization. With the presented modular simulation framework consisting of three cooperating packages, all important steps can be provided. Each package is a tool for specific purpose, Magnetic Field Simulator for signal generation, Reconstruction Framework for data reconstruction and 3D Visualization Tool for data visualization, which can be used as framework, stand-alone or in combination with third party software packages
Model-based voltage predictions for arbitrary waveform excitation in Magnetic Particle Imaging
No full textIn recent works, arbitrary waveform or pulsed excitation in Magnetic Particle Imaging (MPI) was proposed to offer better resolution and sensitivity. Generating these excitation fields poses a new challenge in MPI hardware design. This work proposes a method which models the excitation chain as a linear system and predicts the required input voltage for the desired output field. The initial prediction is then iteratively improved to compensate for inaccuracies of the model. The method is demonstrated to achieve accurate field waveforms in both linear and slew rate limited regions of the amplifier