International Journal on Magnetic Particle Imaging (IJMPI)
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Preliminary results: Imaging of in situ labeled Tumor-Associated Macrophages with Magnetic Particle Imaging
No full textTumor-associated macrophages (TAMs) are thought to be protumoral, enhancing and contributing to cancer progression. The presence of TAMs has been correlated with the metastasis of tumor cells and the inhibition of the antitumoral immune responses mediated by T cells. In this brief paper, we used Magnetic Particle Imaging (MPI) to detect passively targeted TAMs homing to a breast cancer model. TAMs were passively targeted using PEG-coated Magnetic Nanoparticles (PEG-MNPs). Escalating doses of PEG-MNPs were tested to evaluate TAM uptake at different time points. An MPI signal was detected in liver and tumor for all the groups except at the lowest dose. A novel quantitation workflow has also been proposed to calculate the quantity of iron inside the different tissues.
Int. J. Mag. Part. Imag. 6(2), Suppl. 1, 2020, Article ID: 2009029, DOI: 10.18416/IJMPI.2020.200902
Evaluation of spatio-temporal resolution of MPI scanners with a dynamic bolus phantom
No full textMagnetic particle imaging (MPI) is a tomographic imaging method to determine the spatial distribution of magnetic nanoparticles (MNP) within a defined volume. To evaluate the spatio-temporal resolution of existing MPI scanners, we developed dynamic MPI measurement phantoms. These segmented flow phantoms consist of a bolus of ferrofluid tracer material, pumped through a tube system. Using a hydrophobic organic carrier oil, cylindrically shaped bolus of different diameter, length, MNP concentrations, and flow velocity can be emulated. Moving boluses were imaged by MPI and the correlation of spatial resolution und velocity of the bolus was investigated. For all bolus dimension and flow velocity combinations, a decreasing spatial resolution and increasing blurring with increasing bolus velocity and decreasing bolus volume was observed.
Int. J. Mag. Part. Imag. 6(2), Suppl. 1, 2020, Article ID: 2009011, DOI: 10.18416/IJMPI.2020.200901
Magnetic Particle Imaging for intraoperative margin analysis in breast-conserving surgery
No full textBreast-conserving surgery (BCS) is a commonly utilized treatment for early stage breast cancers but has high reexcision rates due to post-surgery identification of positive margins. A fast, specific, sensitive, easy-to-use tool for assessing margins intraoperatively has been shown to reduce the need for additional surgeries, and while many techniques have been explored, the clinical need is still unmet. We assess Magnetic Particle Imaging (MPI) for intraoperative margin assessment in BCS, using a passively or actively tumor-targeted iron oxide agent and two hardware devices: a hand-held Magnetic Particle (MP) detector for identifying residual tumor in the breast, and a small-bore imager for quickly imaging the tumor distribution in the excised specimen. In this abstract, we present both hardware systems and demonstrate proof-of-concept detection and imaging of clinically-relevant phantoms
OS-MPI: an open-source magnetic particle imaging project
No full textMagnetic Particle Imaging (MPI) is an emerging imaging modality with a growing research community and commercial foundation. Despite being introduced over a decade ago and having hundreds of associated publications, the bar for entry to the field remains quite high due to instrumentation costs and the inherent design complexity. Here we introduce an open-source project, OS-MPI, with the aim of facilitating entry into the field by providing design details of a field free line (FFL)-based pre-clinical scale imager and supporting systems and software. Our initiative is hosted on GitHub and presents a selection of MPI systems including our small-bore imager, a spectroscopy device, and a magnet winding jig. We will continually update as our designs evolve and encourage community-driven development. For each system, we describe all relevant mechanical and electrical designs, design rationale and simulations, assembly guidelines, and a parts list and cost breakdown.
Int. J. Mag. Part. Imag. 6(2), Suppl. 1, 2020, Article ID: 2009059, DOI: 10.18416/IJMPI.2020.200905
Determination of 3D system matrices using a mirroring approach based on mixing theory
No full textOne approach of image reconstruction in MPI is the system matrix based reconstruction. With this approach, in addition to the particle behavior, the sequence and the scanner properties are also calibrated and stored in a system matrix, so that a linear system of equations for the image reconstruction must be solved. However, the measurement of the system matrix is very time-consuming, depending on the desired spatial resolution. Independently of this, there are some remarkable symmetries within the system matrix that could be exploited to significantly reduce the calibration time. In the context of this work the theoretical description of a system matrix about Chebyshev polynomials is used to completely build a 3D system matrix by mirroring an octant and to successfully reconstruct an image.
Int. J. Mag. Part. Imag. 6(2), Suppl. 1, 2020, Article ID: 2009051, DOI: 10.18416/IJMPI.2020.200905
Dynamic concentration reconstruction for magnetic particle imaging using splines
No full text4D Magnetic Particle Imaging (MPI) reconstructions with high temporal resolution are of high relevance for diagnostic purposes. In multi-patch measurements the data for single patches is not continuous. During the scan of one patch no data is acquired for the remaining patches. This impedes regularization by similarity of subsequent frames. We propose a method that models the dynamic tracer concentration with cubic B-splines which allows for reconstructions with high temporal resolution from only few frames.
Int. J. Mag. Part. Imag. 6(2), Suppl. 1, 2020, Article ID: 2009049, DOI: 10.18416/IJMPI.2020.200904
Co-optimisation of send and receive coils
No full textMagnetic particle imaging exploits the nonlinear magnetization behaviour of iron oxide nanoparticles, by modulating the magnetic flux density of those particles. This modulation is achieved by creating time-varying magnetic fields using a drive coil. The generated signal is picked up with a receive coil. In order to minimize mutual influence, those coils need to be optimized. The decision process for an optimal combination of drive and focus field coil and the receive coil is described with respect to the signal chain and power consumption of the scanner. It is shown that the advantages of longer coils result in a linear increase of the power loss in the scanner, while the obtained sensitivity no longer increases relevantly. Based on this analysis a coil with favourable cost-benefit ratio can be chosen.
Int. J. Mag. Part. Imag. 6(2), Suppl. 1, 2020, Article ID: 2009037, DOI: 10.18416/IJMPI.2020.200903
Characterization of noise and background components in MPI raw signals
No full textInterfering noise and background signals deteriorate the image quality of magnetic particle imaging (MPI). In this work, we present the detailed characterization of noise and background factors interfering the acquired MPI raw signals. Empty scanner measurements were obtained to analyze the temporal variations in the short-, mid- and long-term regime. These results form the basis to improve the mandatory understanding of these unwanted signal components to become able to remove or minimize their impact on image reconstruction
Int. J. Mag. Part. Imag. 6(2), Suppl. 1, 2020, Article ID: 2009028, DOI: 10.18416/IJMPI.2020.200902
Mag-Guider: permanent magnet systems to steer and image super-paramagnetic particles
No full textPermanent magnet systems are used for guiding superparamagnetic (nano)particles (SPP) on arbitrary trajectories over large volumes. The basic idea is to use two superimposed magnetic fields: one constant to magnetize and orient the particles, and the other with a constant gradient to exert a force. Changing the angle between them enables steering with constant force at a single angle/direction. The same instrument can also be used for magnetic resonance imaging (MRI) using the inherent contrast of the SPP.
The idea was realized by combining Halbach-cylinders of dipolar and quadrupolar configuration. Prototypes of various sizes and complexity were constructed for different applications (e.g. light-microscopy). An advanced system with two quadrupoles even allows canceling the force, hence stopping the SPP and moving them around sharp edges. This system also allows for MRI and some first experiments are presented. The velocity of SPPs under such conditions was also investigated and modelled.
Int. J. Mag. Part. Imag. 6(2), Suppl. 1, 2020, Article ID: 2009026, DOI: 10.18416/IJMPI.2020.200902
MPI based intracranial pressure (ICP) monitor for hydrocephalus patients
No full textIntraventricular shunts are the conventional medical devices for the treatment of hydrocephalus. The most common and life threatening complication of the implanted devices is the probability of the blockage or the misalignment of shunts after the implantation procedure. The most common way to diagnose these complications is the application of Computed Tomography. Unfortunately, frequent exposure to x-ray radiation can have degrading effects such as memory loss, stroke-like symptoms, poor brain function and even it can lead to cancer. In this study, an elastic capsule filled with super paramagnetic iron oxide nanoparticles is used for the measurement of the intracranial pressure (ICP). The diameter of the capsule is measured by the magnetic particle imaging method (MPI). The performance of the proposed method is evaluated with a Matlab/SIMULINK model.
Int. J. Mag. Part. Imag. 6(2), Suppl. 1, 2020, Article ID: 2009074, DOI: 10.18416/IJMPI.2020.200907