International Journal on Magnetic Particle Imaging (IJMPI)
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Design and safety considerations of I/O modules
No full textIn Magnetic Particle Imaging, numerous data inputs and outputs are required to receive and process signalsfrom the feedback and receive coils, and to control the output associated with the drive and selection field coils.Previously used conventional input/output (I/O) boards have shown limitations in regard to the initial start-upprocedures, safety assurance and usability. In order to address these issues, a more sophisticated I=O-Unitwas designed, incorporating and expanding the functionality of twelve measurement cards. These cards arehoused within the I=O-Unit as shielded, interchangeable modules and built up as synchronised multi channelI/O system
Separating Nanoparticle Induced Delays from Relaxation Time Constant in TAURUS
No full textMagnetic nanoparticles (MNPs) exhibit relaxation behavior, introducing a delay in their magnetization alignment.The TAURUS method enables simultaneous estimation of the signal delay and the effective relaxation time constant.In this study, we propose a method to separately estimate the MNP induced delay and the system induced delay.We then demonstrate that the MNP induced delay and the relaxation time constant estimated via TAURUS showdifferent trends, implying that they capture different aspects of the MNP response
A study of flow dynamics in a realistic aneurysm phantom using MPI, MRI and OT
No full textThe flow dynamics in a realistic aneurysm phantom were investigated using real-time 3D Magnetic Particle Imaging (MPI). As reference, the flow dynamics were determined using Optical Transmission (OT) and 4D flow Magnetic Resonance Imaging (MRI). The measured flow dynamics with MPI, OT and MRI are in good agreement
Phase-sensitive signal processing in the DiffMag handheld probe
No full textSentinel Lymph Node Biopsy (SLNB) is a surgical procedure that employs a tracer and a handheld detection device to assess lymphatic metastasis. Superparamagnetic iron oxide nanoparticles (SPIONs) have been used as tracers, with handheld magnetometers utilised for detection. The differential magnetometry processing technique (DiffMag) effectively suppresses interference from stationary magnetic materials. However, movement of magnetic materials introduces signal artefacts---referred to as motion artefact---due to the sequential nature of the processing technique. Continuous manoeuvring of surgical equipment during SLNBs generates such artefact, potentially extending surgery time. To address this drawback, we propose an extension of DiffMag using phase-sensitive signal processing to measure phase lag---a property unique to signals from SPIONs. This extension demonstrates potential to differentiate SPION signals from motion artefacts. In this study, we examined phase lag across various SPION types (Magtrace, Resotran, Resovist, Ferrotrace) within clinically relevant parameter for SLNB, including low SPION concentrations and increased environmental viscosity. Implementing the processing technique in the DMH yielded highly stable phase measurements characterised by low noise levels and negligible drift. Notably, SPIONs across all tested conditions exhibited a distinct measurable phase difference to those of motion artefacts. In conclusion, phase-sensitive signal processing utilised in the DMH-probe demonstrates strong potential for differentiating SPION signals from motion artefacts
Improved image quality with a receive-only coil for the Bruker MPI scanner
No full textSensitivity and resolution in MPI depend, amongst others, on the used scanner hardware and the iron concentration in the measured sample. Typically, to reconstruct samples with low iron amount, in the system matrix (SM) based reconstruction, only low frequency components with high signal-to-noise ratio are used, which limits the achievable spatial resolution. Here, Bruker’s preclinical MPI scanner is used to compare the image quality of samples at decreasing iron concentrations measured with either the built-in transmit-receive (TxRx) coil or a dedicated smaller receive-only (Rx) coil. The results show that the Rx coil allows visualization of significantly lower iron concentrations. Additionally, the image quality of measurements with the TxRx coil can be enhanced by using the SM of the Rx coil for reconstruction, which is beneficial for objects that do not fit into the Rx coil
Three-Dimensional Magnetic Particle Imaging Resolution Enhancement Method Based on Structured Distillation Contrast Learning
No full textMagnetic Particle Imaging (MPI) is a novel imaging technique for visualizing the spatial distribution of magnetic nanoparticles. Due to variations in gradient field strength and scanning trajectories, MPI resolution shows anisotropy. This paper presents CSDNet, a model based on structured distillation contrast learning. It extracts low-resolution directional features from a two-dimensional isotropic teacher network to guide the training of the student network and improve the resolution in three dimensions through deblurring. The introduced contrast loss significantly improves the ability to extract image details. Experimental results confirm CSDNet’s superior performance in detail recovery and accuracy
Model-Based Reconstruction in MPI accounting for Field Imperfections
No full textTo date a system matrix has to be obtained through a tedious calibration measurement when employing a system matrix-based reconstruction in magnetic particle imaging. This problem can be effectively addressed by model-based reconstruction, which takes into account both particle and scanner parameters. In this study, we focus on the scanner parameters and in particular on the fact that the fields of experimental systems are imperfect. For experimental Lissajous-type data we show that the modeling error can be substantially reduced by about 18% by incorporating field imperfections in both the transmit and receive coils
Efficient solvers for coupled Brown-Néel Fokker-Planck equations
No full textIn magnetic particle imaging (MPI), achieving efficient and accurate solutions to forward models is crucial for solving inverse problems. This work investigates the coupled Brown/Néel model, which leads to a convection-dominated Fokker-Planck equation defined over a higher-dimensional domain. To handle these challenges, we propose a joint angular-temporal discretization of this partial differential equation (PDE) combined with a reduced basis approach. Preliminary numerical results on simplified models demonstrate the efficacy of our approach, indicating its potential for broader applications in MPI
Advancing clinical MPI: safety assessment of medical implants in a human cadaver model
No full textMagnetic Particle Imaging (MPI) is a 3D imaging technology that offers high temporal resolution without ionizing radiation, making it ideal for cardiovascular imaging and the real-time visualization of endovascular interventions. A key safety concern is the potential heating of metallic implants during MPI scans. This study evaluated the thermal behavior of various commercially available medical implants in a perfused human cadaver model. The measurements showed no detectable heating of the tested endovascular devices. A temperature increase of 0.04 K was observed in the tested femoral gamma nail. The study concludes that some commercial medical implants do not heat significantly in the used MPI scanner-setup under realistic conditions, indicating their safety for clinical use
Comparison of receive inserts for non-human primate fMPI in a human brain scanner
No full textThe receive coil geometry significantly influences MPI detection sensitivity, a primary distinguishing characteristic when competing with other tracer-based imaging methods. Here, we compare four gradiometric receive inserts for non-human primate functional MPI to identify a coil geometry that maximizes sensitivity while accommodating the primate head. A cylindrical coil with a diameter of 14 cm provided the highest sensitivity while fitting the macaque. Smaller cross-section gradiometers offered better rejection of noise originating from the shift coil amplifiers