Authors: Can Barış Top

We present the design and measurement results for the selection field generation of an open scanner configuration for field free line (FFL) magnetic particle imaging. The FFL can be rotated electronically using the designed coils. The selection of the imaging plane is possible by asymmetrical excitation of the upper and lower coil groups. The gradient of the magnetic field is orthogonal to its gradient, allowing 2D scan using a single drive coil channel. The mechanical housing of the coils are manually adjustable to provide the highest gradient level for the imaged object size. In the current configuration, a magnetic field gradient between 0.5 T/m - 0.74 T/m can be generated in a 60 mm diameter field of view. (Submission 430)

Authors: Yasushi Takemura, Suko Bagus Trisnanto

Magnetic particle imaging (MPI) requires high field gradient to acquire sharp point spread function used to refine spatial resolution for submillimeter imaging of cells and small animal models. Since the steep field gradient potentially causes difficulty in the sample handling and the signal processing, minimizing the field gradient is more practical even though it degrades the spatial resolution. By modulating relaxation responses of magnetic nanotracers at two distinctive frequencies: 2 kHz and 1MHz, we reconstructed images of Resovist® sample placed in a 1.4×1.4 mm2 field of view. This modulated MPI implements 2 sets of permanent magnets of which the same polarity faces one another to create a 2 Tm-1 symmetrical field gradient on the xy plane and 3 Tm-1 on the z axis. Although the spatial resolution appears poor to differentiate two-neighboring circular phantoms of dense liquid samples, we could visualize a 1-mm ring-shaped solid sample with 0.1 mm thickness. (Submission 427)

Authors: Florian Thieben, Marija Boberg, Patryk Szwargulski, Matthias Graeser, Tobias Knopp

Large selection-field power is required to generate a sufficient gradient strength in Magnetic Particle Imaging (MPI). Without cooling, the subsequent heat generation can limit the maximum experiment time. For commercially available MPI scanners a lot of effort was put into active cooling requiring space and infrastructure to dissipate heat. In this abstract, a promising power handling for the selection-field generation is presented. Using a pulsed instead of a continuous selection-field the gradient strength can be increased and no active cooling is required. (Submission 491)

Authors: Tuan-Anh Le, Minh Phu Bui, Jungwon Yoon

Magnetic Particle Imaging (MPI) is a fast and sensitive imaging method that can be used to measure the spatial distribution of superparamagnetic iron oxide (SPIO) nanoparticles. To overcome some limitations of general MPI, the Amplitude Modulation MPI (AM MPI), which uses a low-amplitude excitation field combined with a low-frequency drive field, was suggested. In this paper, we present the design of a rabbit scale 3D AM MPI system with a larger bore size (9 cm). The AM MPI can reach a drive-field field-of-view (DF-FOV) of 4.00 x 4.00 x 8.00 cm and a whole field-of-view (W-FOV) of 6.36 x 6.36 x 8.00 cm at 2.2 T/m. (Submission 521)

Authors: Kulthisa Sajjamark, Jochen Franke, Rainer Pietig, Heinrich Lehr, Volker Niemann

Aiming to increase spatial selectivity which provides the precision in hyperthermia therapy and high resolution in imaging, we propose a strategy to increase field gradient for Magnetic Particle Imaging (MPI) modality. In this study, a solution for an existing MPI system topology was simulated, which uses additional soft magnetic material as iron core retrofit at the center of selection field coil. Due to core property of high magnetic permeability relative to air, magnetic flux gets confined to increase selection field gradient field slope. Within this simulation study, the optimal core position is evaluated whilst its effects on the magnet system is validated. We found that this technique increases the magnetic field gradient up to a factor of 1.4 from 2.5 T/m to 3.4 T/m in z-direction, without significant loading of the drive field resonance circuit due to power losses caused by eddy currents in the MPI compatible iron core shielding. (Submission 429)

Authors: Thilo Viereck, Sebastian Draack, Melvin Kuester, Meinhard Schilling, Frank Ludwig

This contribution presents initial imaging experiments with a newly designed imaging setup that facilitates Magnetic Particle Imaging (MPI) by recording the step response of the tracer in contrast to its higher harmonic spectrum. Such a concept promises a greatly reduced complexity in hardware and enables a much simpler time-domain evaluation of the receive signals. The concept borrows from magnetorelaxometry (MRX) subjecting the tracer to a step change in excitation field to affect a relaxation of the particles’ magnetization. For that reason, all experience from MRX data evaluation and modeling of the magnetization response apply to the imaging variant as well. The hardware design of the system opens a great deal of flexibility regarding excitation patterns and signal evaluation for future experiments. (Submission 511)

Authors: Semih Kurt, Vagif Abdulla, Emine Ulku Saritas

In magnetic particle imaging (MPI), standard x-space reconstruction requires partial field-of-view (pFOV) processing steps: speed compensation of the received signal and gridding the non-equidistant field free point (FFP) positions to a Cartesian grid. Moreover, due to direct feedthrough filtering, a DC recovery algorithm must be utilized, which requires pFOVs to overlap with each other. In this work, we propose an alternative x-space reconstruction technique that does not require pFOV processing or overlapping pFOVs. The proposed technique is applicable to rapid and sparse multi-dimensional scanning trajectories where standard x-space reconstruction cannot be applied due to non-overlapping pFOVs. (Submission 514)

Authors: Christina Brandt, Inga Glöckner, Martin Möddel, Tobias Knopp

Multi-contrast magnetic particle imaging (MPI) enables the determination of different contrasts in addition to the particle concentration. For instance it is possible to discriminate multiple tracer types that differ e.g. in the particle core size. One challenge of multi-contrast MPI is that the reconstruction problem is severely ill-posed such that in practice a perfect separation of different tracer types is not achieved. In this work, we develop a method for improving the channel separation and in turn prevent leakage from one channel into the other. Our approach exploits sparsity in both the spatial and the channel dimension. By developing a tailor regularization approach for improved multi-contrast reconstruction, we show that it is possible to significantly reduce signal leakage. (Submission 489)

Authors: Florian Lieb, Tobias Knopp

The image reconstruction in Magnetic Particle Imaging (MPI) relies on efficiently solving an ill-posed inverse problem. Current state-of-the-art reconstruction methods are either based on row-action methods with fast convergence but limited noise suppression or advanced sparsity constraints showing better image quality, but suffering from a higher computational complexity and slower convergence. In this contribution, we propose a novel row-action framework where advanced sparsity constraints, e.g., a combination of L1- and TV-norm, can be included. Its performance is numerically evaluated on simulated and real MPI data, showing a significant reduction of computation time while retaining the enhanced imaging quality.   (Submission 397)

Authors: Tobias Kluth, Patryk Szwargulski, Tobias Knopp

The MPI image reconstruction problem requires, particularly for 2D and 3D excitation patterns, a measured system matrix due to the lack of an accurate model that is capable of describing the nanoparticles’ magnetization behavior in the MPI setup. Here we exploit a model based on Néel rotation for large particle ensembles and we find model parameters that describe measured 2D MPI data with much higher precision than state of the art MPI models, which is also illustrated in phantom experiments. This is a short summary of the recent work [4] to which we refer to for all further details. (Submission 406)

Authors: Marco Maass, Christine Droigk, Alfred Mertins

In a recent publication, based on the Langevin model, the exact mathematical relationship between the system function and tensor products of Chebyshev polynomials of second kind has been derived for the case in which multidimensional excitation is used for magnetic particle imaging. There, a new expression for the system function in magnetic particle imaging was derived. To make this representation easily accessible, the present paper focusses on the more practical aspects of the theory without going deep into the mathematical proofs.  In particular, we examine the contribution of the mixing factors to the total energy of a system function component. (Submission 486)

Authors: Hannes Albers, Tobias Kluth, Tobias Knopp

In the context of system function modeling for magnetic particle imaging, computing fast and accurate approximations to the time evolution of magnetic nanoparticles' (MNPs) mean magnetic moment is a problem of interest. In a software toolbox we comprise algorithms and methods that can simulate Brownian and Néel rotation of MNPs' magnetic moments that can be used to obtain more accurate model-based system matrices than those relying on the so-called equilibrium model. We present and discuss results obtained with these implementations which are made available in the software toolbox under github.com/MagneticParticleImaging/MNPDynamics.jl to inspire further research in these directions (Submission 435)

Authors: Alexander Neumann, Thorsten M. Buzug

To simulate the behavior of realistic magnetic particles in magnetic particle imaging it is not enough to perform simulations assuming only a uniaxial magnetic anisotropy energy due to the complex coupling between the magnetic and the mechanic degrees of freedom of the particle in multidimensional excitation fields. Most particles can only be approximated of having uniaxial magnetic anisotropy energy. As such, this work will discuss the shortcoming of currently used models focusing on only uniaxial anisotropy and show how a theoretical model must be defined to allow for arbitrary anisotropy energies. First simulation results showing the differences between different anisotropy energies will be presented at the workshop. (Submission 462)

Authors: Jing Zhong, Meinhard Schilling, Frank Ludwig

A new approach of simultaneous imaging of magnetic nanoparticle (MNP) concentration, temperature and viscosity with a custom-built scanning magnetic particle spectrometer (SMPS) is presented. The fundamental f0 and the 3f0 and 5f0 harmonics of the MNPs dominated by Brownian relaxation are measured with the SMPS. The effects of viscosity and temperature on the harmonics are studied in ac magnetic fields with different frequencies and amplitudes. Afterwards, phantom experiments are performed on the MNP samples with different spatial distributions of viscosity and temperature, which demonstrates the feasibility of the proposed approach for simultaneous imaging of MNP concentration, temperature and viscosity imaging. (Submission 433)

Authors: Erica Mason, Eli Mattingly, Konstantin Herb, Sofia Franconi, Monika Sliwiak, Clarissa Cooley, Lawrence Wald

Breast-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. (Submission 407)

Authors: Florian Griese, Peter Ludewig, Cordula Gruettner, Florian Thieben, Knut Müller, Tobias Knopp

Magnetic Particle Imaging (MPI) is used to visualize the distribution of superparamagnetic nanoparticles within 3D volumes with high sensitivity in real time. Recently, MPI is utilized to navigate micron-sized particles and micron-sized swimmers, since the magnetic field topology of the MPI scanner is well suited to apply magnetic forces. In this work, we analyze the magnetic mobility and imaging performance of nanomag/synomag-D for Magnetic Particle Imaging/Navigation (MPIN). With MPIN the focus fields are constantly switching between imaging and magnetic force mode, thus enabling quasi-simultaneous navigation and imaging of particles. In flow bifurcation experiment with a 100 % stenosis on one branch, we determine the limiting flow velocity of 1.36 mL/s, which allows all particles to flow only through one branch towards the stenosis. During this experiment, we image the accumulation of the particles within the stenosis. In combination with therapeutic substances, this approach has a high potential for targeted drug delivery. (Submission 445)

Authors: Anna C. Bakenecker, Klaas Bente, Felix Bachmann, Anselm von Gladiss, Damien Faivre, Thorsten M. Buzug

Magnetic beads can serve as drug carries or agents for hyperthermia. For a precise treatment, the magnetic beads need to be steered towards their targeted position. Magnetic objects can be moved by either a magnetic gradient field or by a homogeneous magnetic field with a rotating field vector. Both, a gradient field and a homogeneous field, act on all magnetic objects similarly and therefore a selection between various objects is not possible. Here we show a selective actuation of magnetic beads by superimposing a gradient field with a rotating homogeneous field. With the selection field, forming a field free point, and the focus field with rotating field vector of an MPI scanner, selective actuation is performed. Since tomographic imaging is essential for the real-time tracking of the actuation process, we demonstrate the feasibility to visualize the magnetic beads with MPI before and after actuation. (Submission 417)

Authors: Marco Gerosa, Gang Ren, Yanrong Zhang, Patrick Goodwill, Jim Mansfield, Pasquina Marzola, Max Wintermark

Tumor-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. (Submission 458)

Authors: Julia Wernecke

In this work, we investigate the suitability of MPI as a volumetry tool for the determination of retrograde voiding cystography of the bladder. Measurements were performed in two different experimental coil settings: first with a novel gradiometer providing three orthogonal channels and second a single-channel gradiometer at varying gradient strengths. The volumes were calculated using two different approaches: a calibration approach based on the amount of SPIOs and a threshold approach. We show that with both approaches MPI volumetry is feasible. Finally we present initial in vivo results of a retrograde voiding cystography in rats. (Submission 504)

Authors: Marija Boberg, Tobias Knopp, Martin Möddel

The reconstruction of multi-patch magnetic particle imaging data requires a compromise between image quality and calibration time. While optimal image quality is ensured by the joint reconstruction approach, a system matrix needs to be acquired for each patch. One can reuse system matrices by shifting them in space, which decreases the calibration effort but leads to distortions due to field imperfections. In this work, we introduce a method for reducing displacement artifacts in the efficient joint multi-patch reconstruction. Based on the magnetic fields we propose a mapping that warps the central system matrix to capture the spatial displacement of off-center system matrices. In this way, we can maintain the low calibration time while significantly improving the image quality. (Submission 459)

Authors: Yvonne Blancke Soares, Ksenija Gräfe, Kerstin Lüdtke-Buzug, Thorsten M. Buzug

A one-sided arrangement of the components relevant for magnetic particle imaging leads to improved patient access, as the object size can be unlimited. In this paper, we further investigate the properties of the single-sided MPI system published earlier. A phantom with up to five positions filled with Perimag particles was rotated to evaluate the spatial resolution depending on the orientation of the receive coils. The reconstruction was done with a Kaczmarz algorithm and a Tikhonov regularization with individually calculated regularization parameters for each measurement. The penetration depth and the spatial resolution in the y-,z-plane were evaluated. (Submission 490)

Authors: Alper Gungor, Can Barış Top

System matrix reconstruction of Magnetic Particle Imaging (MPI) require a time-consuming calibration process. The total number of pixels of the desired image has a direct effect on the calibration time. Although there are various techniques that can shorten the calibration process such as compressive sensing or coded calibration scenes, the increase in total number of pixels still require higher number of samples. In this study, we propose a simple super-resolution technique for MPI images during reconstruction. Using simulations on a field free line MPI scanner system with low drive field amplitude, we show that one can achieve higher resolution images by simply applying super-resolution techniques on the rows of the system matrix. We demonstrate that even simple linear models can help resolve high-resolution structures. (Submission 612)

Authors: Jorge Chacon-Caldera, Heinrich Lehr, Kulthisa Sajjamark, Jochen Franke

Magnetic particle imaging (MPI) offers an exceptional set of advantages including high sampling efficiency and sub-millimeter spatial resolution. The former is maximized using ad-hoc sampling trajectories; the latter relies on the compensation of the point spread function of the superparamagnetic iron oxide particles (SPIOs) necessary for the MPI signal. The System Matrix (SM) approach for reconstruction uses a pre-calibration measurement and achieves both purposes simultaneously, relating the concentration of SPIOs and the particle response to the signal. Consequently, the SM’s quality will largely influence the reconstruction. Considering the multitude of factors involved in the reconstruction, it is difficult to identify sources of image artifacts.  In this work, we demonstrate the potential to use reconstructions of individual measurements within the SM (eigen-reconstruction) as a test for both SM and reconstruction quality. We also present an algorithm to enhance image quality using eigen-reconstructions. (Submission 613)

Authors: Martin Möddel, Florian Griese, Tobias Kluth, Tobias Knopp

Magnetic particle imaging (MPI) is a tracer based tomographic imaging technique that uses static and oscillating magnetic fields to generate an image contrast from the spatial distribution of magnetic nanoparticles. Recent investigations have shown that the MPI is able to generate additional contrasts from different tracer materials or their environments. For example, multi-contrast MPI can be used to determine the viscosity or temperature of the particle environment, or to distinguish tracer particles based on their core size. In this work, we investigate a novel contrast based on the magnetic anisotropy of immobilized particles which allows to estimate the orientation of samples. (Submission 440)

Authors: Mustafa Utkur, Emine Ulku Saritas

In magnetic particle imaging (MPI), the relaxation behavior of the nanoparticles has been exploited to expand quantitative mapping capabilities of MPI to applications such as viscosity mapping and temperature mapping. We have previously proposed a technique called TAURUS to estimate the relaxation time constant directly from the MPI signal, and demonstrated its viscosity mapping capabilities via imaging experiments. In this work, we extend TAURUS to demonstrate its temperature mapping capability via 1D imaging experiments at two different temperatures. (Submission 520)

Authors: Semih Kurt, Yavuz Muslu, Emine Ulku Saritas

In magnetic particle imaging (MPI), different magnetic nanoparticles (MNPs) in the same field-of-view can be distinguished via color-MPI techniques. Existing system-function-based techniques require extensive calibration scans, whereas x-space-based approaches require either multiple scans at different drive field parameters, or rely on the underlying mirror symmetry of the adiabatic MPI signal. In this work, we propose a novel blind source separation technique for multi-color MPI, exploiting the distinct signal delays of different MNPs. The proposed technique blindly decomposes the MPI signals from different MNPs, which can then be individually reconstructed and assigned to separate color channels to form a multi-color MPI image. (Submission 506)

Authors: Mert Şener, Barış Oğuz Gürses, Özge Akbülbül, Aysun Baltacı

Intraventricular shunts are the conventional medical devices for the treatment of hydrocephalus. The most common and life treating complication of the implantation of these devices is the probability of the blockage or the misalignment of shunts after the surgery. The most command way to diagnose these complications is the application of Computed Tomography. Unfortunately, frequent exposure to x-ray radiation can have degrading effects in the heath of these patients and even, it can lead to the cancer.   Magnetic Particle Imaging is a tracer based imaging modality and has no adverse effects on health as x-ray based methods. In this study, an elastic capsule filled with super paramagnetic iron oxide nanoparticles is used for the measurement of the intracranial pressure. The diameter of capsule is measured by the magnetic particle imaging method. (Submission 615)

Authors: Stephan Müssig, Florian Fidler, Daniel Haddad, Karl-Heinz Hiller, Susanne Wintzheimer, Karl Mandel

Marking and identification of materials is becoming increasingly important due to complex global resource and supply chains. In this work, a miniaturized magnetic marking technology based on so-called supraparticles is presented. The hierarchical buildup of these microparticles, which are assembled from nanoparticles, allows to precisely tailor their structure. Superparamagnetic iron oxide nanoparticles as building blocks are used in this work. By surface modification and mixing them with silica nanoparticles, respectively, the supraparticle structure is varied. It is demonstrated that these structural modifications are readily detected by magnetic particle spectroscopy (MPS). Thereby, various distinguishable magnetic signals are feasible, which are even detected after incorporation into dark plastic. The presented magnetic marking technology thus proves its potential as an alternative marking technology to optical labels. (Submission 405)

Authors: Ecrin Yagiz, Mustafa Utkur, Can Barış Top, Emine Ulku Saritas

In magnetic particle imaging (MPI), the information about the local environment, such as its viscosity and temperature, can be inferred via the relaxation behavior of the nanoparticles. As the nanoparticle signal also changes with drive field (DF) parameters, one potential problem for quantitative mapping applications is the optimization of these parameters. In this work, an accelerated framework is proposed for characterizing the unique response of a nanoparticle under different environmental settings. The proposed technique, called magnetic particle fingerprinting (MPF), rapidly sweeps a wide range of DF parameters, mapping the unique tau-fingerprint of a sample. This technique can enable simultaneous mapping of several parameters (e.g., viscosity, temperature, nanoparticle type, etc.) with reduced scan time. (Submission 471)
 

Authors: Franz Wegner, Anselm von Gladiss, Julian Haegele, Ulrike Grzyska, Malte Sieren, Kerstin Lüdtke-Buzug, Jörg Barkhausen, Thorsten Buzug, Thomas Friedrich

Restenoses are a common problem after stent implantations and may cause new ischemic events, e.g. heart attacks and strokes. Thus, early diagnosis and treatment of in stent stenoses has tremendous clinical impact. Visualization and quantification of the stent lumen with the established noninvasive imaging modalities MRI and CT is severely limited by stent induced artifacts. The aim of this study was to investigate whether MPI can quantify the stent lumen accurately. (Submission 437)

Authors: Ulrike Grzyska, Thomas Friedrich, Julian Haegele, Thorsten M Buzug, Joerg Barkhausen, Franz Wegner

Aortic coarctation is a potentially life-threatening disease in newborns that requires early treatment. Recently, a new stent was developed for this purpose, which can be redilatated and thus adapted to the growth of the infant’s aorta. Due to the lack of ionizing radiation MPI is a very promising imaging technique for this clinically very important application in children. Therefore, the safety of this stent with regard to heating by oscillating magnetic fields must be investigated before the stent can be used. (Submission 455)

Authors: Benedikt Mues, Brice Tiret, Benedict Bauer, Jeanette Ortega, Thomas Gries, Thomas Schmitz-Rode, Patrick Goodwill, Ioana Slabu

In this study, we evaluate the hyperthermia efficiency of polypropylene (PP) fibers with incorporated magnetic nanoparticles (MNP), which are used to develop inductive heatable stents in cancer therapy. Further, we investigate their depiction in magnetic particle imaging (MPI). We show that the intrinsic loss power (ILP) value depends on the MNP agglomeration state and their concentration inside the fibers, while the intensity values in the MPI images show a linear response with MNP concentration. We conclude that MNP dynamic magnetic behavior strongly changes with different MNP agglomeration states and magnetic field settings. (Submission 443)

Authors: Konstantin Herb, Erica E. Mason, Eli Mattingly, Joseph B. Mandeville, Emiri T. Mandeville, Clarissa Zimmerman Cooley, Lawrence L. Wald

MPI has been proposed as an alternative to fMRI for detecting cerebral blood volume (CBV) changes associated with brain activation due to potentially higher sensitivity, possibly enabling single-patient studies. In this work, we show preliminary neuroimaging data of CBV modulation with hypercapnia acquired in vivo on a rodent MPI scanner designed for time-series imaging. This continuously rotating 2D projection field free line imager enables time-series imaging with temporal resolution of up to 3 seconds. As a first demonstration of “fMPI”, we acquire time-series images of a rodent brain with 5 second temporal resolution with the animal undergoing alternating 3-minute periods of either hyper- or hypocapnia.  Image intensity changes from CBV modulation of the injected SPIONs concentration were detected with a CNR of up to 14 in brain pixels. (Submission 421)

Authors: Eli Mattingly, Erica Mason, Konstantin Herb, Monika Śliwiak, Katrin Brandt, Clarissa Cooley, Lawrence Wald

Magnetic 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. (Submission 508)

Authors: Matthias Gräser, Tom Liebing, Patryk Szwargulski, Fynn Förger, Florian Thieben, Peter Ludewig, Tobias Knopp

Magnetic particle imaging is a very useful tool in the detection of stroke. To study the ability of stroke in a mouse model the data acquisition is challenging as a mouse brain contains only a very small ratio of blood compared to large animals or humans. The effective concentration within the whole organ is therefore very small, especially compared to the heart or the liver. Typical MPI receiver coils however cover a sensitive region of around 30 mm to 50 mm and have a bore size of above 40 mm. This leads on the one hand to non-optimal signal coupling due to the distance to the particles and on the other hand strong signals from the heart can cause artifacts in the low signal regions. In this work we present a coil optimized for mouse brain imaging, which due to its small size, also dampens signal from regions outside of the coil. (Submission 480)

Authors: Jason Pagan, Juehao Lin, Alexey A Tonyushkin

A single-sided MPI scanner holds a great promise for a variety of clinical applications. In such a scanner the SPIOs response to the excitation is detected by a planar receive coil on the surface of the device. Due to a single-sided geometry, differentiating a small signal on a strong excitation background becomes a challenging task and further impinges the potential sensitivity gain, thus we implemented a new planar gradiometer receive coil configuration for our MPI scanner. The preliminary results imply the improved sensitivity of the device over the traditional single coil design. (Submission 469)

Authors: Ahmet Rahmetullah Çağıl, Bilal Tasdelen, Emine Ulku Saritas

In a magnetic particle imaging (MPI) scanner, utilizing a tunable gradiometer receive coil can aid in achieving greater degree of decoupling of direct feedthrough signal. However, such a coil can be hard to tune since a very precise positioning of the compensation segment is necessary for excellent decoupling. In this work, we present a doubly tunable gradiometer coil capable of fine tuning without loss of tuning range. We show with experimental results this design can achieve an effective 81.4 dB decoupling in comparison to an identical coil with no gradiometric compensation. (Submission 517)

Authors: Silvio Dutz, Anton Stang, Lucas Wöckel, Olaf Kosch, Patrick Vogel, Cordula Grüttner, Volker C. Behr, Frank Wiekhorst

Magnetic 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. (Submission 423)

Authors: Matthias Weber, Daniel Hensley, Blayne Kettlewell, Andrew Mark, Ryan Orendorff, Maximilian Peters, Brice Tiret, Elaine Yu, Patrick Goodwill

In magnetic fluid hyperthermia (MFH), Magnetic Nanoparticles (MNPs) dissipate heat when exposed to alternating magnetic fields (AMF). MFH is used for targeted energy deposition for targeted drug-delivery or cancer therapy. To avoid heat deposition in all areas with high particle concentration, a gradient field featuring a field-free area (FFR) can be utilized to isolate heating a target region. In this work, we present preliminary results with a localized hyperthermia system, HYPER, that features a mechanically actuated gradient that enables adjusting the heating region’s size and position. The size of the heating region in our prototype is verified by measuring the full width at half maximum (FWHM) of the specific absorption rate (SAR) point spread function (PSF) and compared to a theoretical heating model. (Submission 513)

Authors: Huimin Wei, Andre Behrends, Thomas Friedrich, Thorsten Buzug

Magnetic particle imaging (MPI) is a rapidly developing imaging modality, which determines the spatial distribution of magnetic nanoparticles. Magnetic fluid hyperthermia (MFH) is a promising therapeutic approach where magnetic nanoparticles are used to transform electromagnetic energy into heat. The similarities of MPI and MFH give rise to the potential of integration of MFH and MPI. In our previous work, a heating coil insert for the preclinical MPI scanner is designed, which can be utilized to generate a high frequency magnetic field suitable for MFH. The current development of the heating coil insert is presented in this paper. (Submission 496)