International Journal on Magnetic Particle Imaging (IJMPI)
Not a member yet
555 research outputs found
Sort by
Asymmetric cancellation coil array for surface receiving coils in open-sided FFL MPI
No full textMagnetic particle imaging (MPI), as an emerging non-invasive molecular imaging technology, utilizes the nonlinear magnetic response properties of superparamagnetic iron oxide nanoparticles for imaging. Compared to body coils, surface coils provide higher filling factor, which is promising to enhance the receiving sensitivity. The field-free line MPI (FFL MPI) is rotated at multiple angles for reconstructing particle concentration images. Single cancellation coil for surface coil may be reduced in accuracy at different angles due to imperfections in the magnetic field or mechanical errors. In this paper we design an asymmetric cancellation array based on an open-sided FFL MPI system for improving the cancellation failure problem at different angles. The results show that the array cancellation is superior to the individual cancellation
Transmission magnetic particle optical scanning imaging
No full textMagnetic nanoparticles (MNPs) are widely used in biological magnetic imaging such as Magnetic Particle Imaging (MPI) and Magnetic Resonance Imaging (MRI) due to their unique magnetic and chemical properties. However, traditional magnetic imaging often comes with resolution limitations, which are typically determined by the strength of the magnetic field and the ability to spatially encode the magnetic field. To overcome the limitations of spatial resolution, we propose using optical scanning for imaging, which can achieve high imaging resolution while retaining a certain degree of penetration capability. The experimental results show that using optical scanning for MNPs imaging can achieve a resolution of 125 microns in magneto-optical signals within a 5cm * 5cm imaging range, and can penetrate 1mg/ml MNPs solution with a thickness of 1cm. The proposal of this method presents a new approach for high-precision human imaging in the future
Investigating the Limits of Solid-Liquid Phase Differentiation in Multi-Color Magnetic Particle Imaging
No full textMulti-color Magnetic Particle Imaging (MPI) offers the ability to distinguish magnetic nanoparticles (MNPs) based on their physical states, enhancing its use in functional imaging and interventional guidance. This study explores the limits of solid-liquid phase differentiation in multi-color MPI. A customized MPI setup was used to test mixed-phase samples, highlighting the relationship between the solid-liquid phase differentiation resolution and system detection resolution. Results show that improving solid-liquid phase differentiation requires both point spread function (PSF) optimization and increased system detection resolution
Measurement-based Synthesis of Field Free Line Trajectory Data
No full textCalibrating Magnetic Particle Imaging systems is time-consuming when done with a robot. Synthesizing calibrationdata from fast calibration measurements can be a significant advantage when dealing with multiple magneticparticle types and trajectories. An approach for this synthesis is presented and evaluated using measured data froman arbitrary waveform Magnetic Particle Spectrometer
DC Bias for Improved Baseline Acquisition on a Magnetic Particle Spectrometer Setup
No full textMagnetic particle spectrometer (MPS) setups typically feature a manually adjusted receive coil to minimize direct feedthrough interference. These adjustments can be compromised when a sample is physically inserted into the MPS setup or when a lengthy experiment is performed. In this work, we propose an MPS setup with a DC bias coil that can completely saturate the magnetic nanoparticle (MNP) signal, enabling baseline signal acquisition when the MNPs are inside the receive chamber
Magnetic Staging in Sentinel Lymph Node Procedures: Insights from the LowMag Trial
No full textAccurate identification of metastatic sentinel lymph nodes (SLNs) is essential for cancer prognosis and treatment planning. In the LowMag clinical trial, a magnetic sentinel lymph node biopsy (SLNB) procedure was implemented in patients with invasive breast cancer. This study evaluates the iron content and AC magnetic susceptibility of SLNs containing magnetic tracer to differentiate between metastatic and non-metastatic SLNs.
Two magnetic detection devices, the superparamagnetic quantifier (SPaQ) and the differential magnetometer handheld (DMH) probe, were used to measure iron content and magnetic susceptibility of individual SLNs. Additionally, ex vivo low-field MRI and detailed histopathology were conducted. A total of 37 SLNs from 20 consecutive patients, including four metastatic SLNs, were analysed.
Iron quantification by low-field MRI and histopathology correlated well with measurements from the DMH probe and SPaQ. A statistically significant difference in iron content was observed between metastatic SLNs (N = 4; DMH: 203.12 ± 87.67 ?g , SPaQ: 131.28 ± 53.38 ?g) and non-metastatic LNs (N =33; DMH: 92.47 ± 89.8 ?g, SPaQ: 42.45 ± 46.9 ?g). Moreover, the combination of DiffMag counts with two features derived by SPaQ from the AC susceptibility (ACS) curve - Full Width at Half Maximum (FWHM) and peak value - achieved 66.7% sensitivity for detection metastatic SLNs, 93.3% specificity for non-metastasis detection, and overall accuracy of 90.9%. These numbers for the DMH probe were 75.0% sensitivity, 78.8% specificity, and 78.4% accuracy.These findings suggest that the DiffMag method offers more precise detection of non-metastatic SLNs compared to metastatic ones. Notably, in both DiffMag and ACS modes, the SPaQ device outperformed the DMH probe in terms of specificity and overall accuracy, likely due to its specialized design
How MNP respond to dual-frequency magnetic excitation in viscous media: An in silico study
No full textMagnetic nanoparticles (MNP) enable new biomedical applications as imaging tracers, heating agents or biosensors due to their unique relaxation mechanism in alternating magnetic fields. For assessing MNP suitable for such applications, magnetic particle spectroscopy (MPS) offers a reliable method, dual-frequency excitation adding sensitivity. Biomedical applications, however, rely on MNP use in physiological environments (blood, tissue, etc.) of various viscosities, which could strongly alter the MNP relaxation behavior. In this work, we present our preliminary results of varying viscosity on the relaxation of MNP during dual-frequency MPS, studied with micromagnetic dynamic magnetization simulation
A score-based model guided by signals for magnetic particle imaging reconstruction
No full textMagnetic particle imaging (MPI) can reconstruct the distribution of magnetic nanoparticles (MNPs) from their nonlinear response signals. The traditional system matrix (SM) reconstruction method requires solving an ill-posed inverse problem using hand-crafted regularization terms that demand careful parameter tuning. Here, we proposed a score-based model guided by signals for MPI reconstruction. The measured response signals were embedded to guide the score-based model in sampling specific MPI images from noise. Simulated experiments showed that our proposed method could improve the reconstruction quality
Dual-frequency MPS enables direct MNP size reconstruction: Verification with micromagnetic simulation data
No full textMagnetic Particle Spectroscopy (MPS) allows for direct characterization of magneto-physical properties of magnetic nanoparticles (MNP), which are widely researched as imaging tracers, biosensing units and therapeutic heating agents. All these applications rely primarily on the core size-dependent magnetic particle relaxation dynamics. Therefore, knowledge about core size of any MNP sample is crucial. Dual-frequency MPS increases the characterization potential by considering frequency mixing terms of the received signal of MNP, from which their sizes can be approximated. In this work, preliminary feasibility and interpretation of a proposed size reconstruction method is tested against precisely simulated input data from stochastically coupled Néel-Brownian relaxation modeling using Monte Carlo implementation
Modular Spherical Magnetic Field Sensor Array
No full textThe characterization of magnetic field properties is an important task in magnetic imaging modalities.Emerging multi-coil field generator topologies, generating the gradient field in magnetic particle imaging, pose new challenges.If multiple coils are active, obtaining the current to field relation is not trivial, due to cross-coupling and cross-saturation effects.Singular measurements at certain operating points are not sufficient for a full system description in these non-linear systems.In this work, an adaptable measurement prototype which utilizes multiple magnetic field sensors is presented.The developed device consists of three-axis Hall-sensor ICs located on a spherical surface.Utilizing the solid spherical harmonic expansions the field inside the sphere can be approximated. The combination of high measurement accuracy, straightforward measurement procedures, and modularity enables rapid and reliable measurements