International Journal on Magnetic Particle Imaging (IJMPI)
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Sparse view sinogram restoration network for improving temporal resolution of projection magnetic particle imaging
No full textThe acquisition views of projection magnetic particle imaging (MPI) limit the temporal resolution of tomographic imaging. When the views of projection are insufficient (sparse view), the streaking artifacts will be introduced after filtered back-projection. The current solutions to the sparse view problem in computed tomography can be divided into three categories, iterative reconstruction, image post-processing, and sparse view sinogram restoration. The first one is computationally intensive and the parameters are difficult to determine. The latter two are data-driven deep learning methods that require large-scale trainable datasets. However, the complex features of the image domain will make the network easy to overfit. Therefore, we propose a sparse view sinogram restoration network for MPI to improve the temporal resolution of tomography. We validate the effectiveness of the proposed method on a simulated dataset and outperform iterative reconstruction and image post-processing methods
Magnetic particle imaging of PD-L1 expression in CT26 tumor
No full textImmunotherapy has gained great attention in recent years for its superior antitumor efficacy especially for late-stage tumors, however it suffers from low immunotherapeutic response rate. It is reported that the expression level of PD-L1 is correlated with immunotherapeutic response. The traditional biopsy is invasive and most often randomly sampled, and they cannot accurately reflect the tumor heterogeneity and temporal dynamics in clinics. However, molecular imaging provides chances for noninvasive, dynamic and whole tumor imaging, which can provide the molecular characterization of PD-L1 expression. In this study, anti-PD-L1 antibody was conjugated to the iron oxide nanoparticles to make the PD-L1 targeted imaging probe, abbreviated as aPD-L1@SPIO, which was utilized in combination with magnetic particle imaging (MPI) to image and quantify the PD-L1 expression. The IgG antibody conjugated SPIO was utilized as control probe. The PD-L1 expressing CT26 tumor bearing mice was utilized for MPI, and the imaging probe was administrated through intravenous injection. The MPI imaging was performed at different time points, and the field of view of MPI was chosen below liver. Our targeted PD-L1 MPI imaging data showed that aPD-L1@SPIO, relatively to IgG@SPIO, showed more specific and targeted MPI imaging with longer retention, which was consistent with ex vivo MPI imaging, prussian blue staining and PD-L1 immunohistochemistry. Our study provides us new technique for the highly sensitive, high depth and quantitative imaging for in vivo characterization of immune checkpoint molecular expression in tumors in addition to PET and optical imaging
MPI coil temperature stabilization method based on phase change heat storage technology
No full textIn magnetic particle imaging systems, it is necessary to pass a high current through the coil or to run it for a long time to perform a specific function. These generate a large amount of Joule heat in the coil, which introduces additional thermal noise and reduces the signal-to-noise ratio. In this work, we propose a method to control the coil temperature of magnetic particle imaging device based on phase change thermal storage technology by exploiting the latent heat properties of phase change materials. The simulation experiments show that the method makes the coil temperature remain almost constant and suppresses the problem of temperature variation of the energized wire. Compared with active temperature control methods such as liquid helium cooling , oil cooling and water cooling, this method has the advantages of low cost, small size, and good portability
Magnetic Particle Imaging for in Vivo Imaging of Acute Lung Injury
No full textAcute lung injury leads to impaired of lung function, has a high morbidity and mortality, and the disease burden is large for the patient. Because the lung is a spongy organ with many cavities, this heterogeneity and the position limit the ability of some imaging techniques to lung image. Here we designed a multimode probe that can enrich in the site of acute lung injury and detected it using magnetic particle imaging and fluorescence imaging. Our results displayed that magnetic particle imaging has the potential to be employed for diagnostic imaging of lung diseases and to add new bricks to the imaging of lung
Characterization of magnetic targeting effectivity in an artificial tumor vessel network
No full textMagnetic nanoparticles (MNP) can be used as drug carriers in novel cancer treatment approaches such as magnetic drug targeting (MDT). Computer simulations of MNP in a tumor vessel network under the influence of a magnetic field considering the physical and chemical properties of MNP were established before, however, an experimental validation of these simulations for specific settings is missing. The parameters influencing the targeting effectivity such as MNP concentration, blood flow velocities and different distances of the tumor vessel network to the magnet configuration were varied and a quantitative assessment of the targeting effectivity was performed photometrically determining the resulting iron concentration. Magnetic particle imaging (MPI) was used to analyze the correlation between MPI intensity values and the iron concentration. The parameter study confirmed the previous simulation results for the fixed magnet configuration
Highly flexible gradiometer coil arrangement offering improved passive compensation for multi-frequency MPI
No full textIn Magnetic Particle Imaging (MPI), the acquired receive signal will contain both the superparamagnetic iron oxide nanoparticle (SPION) signal as well as the excitation signal, where the former is to be maximized while the latter is to be reduced. Gradiometer receive coils can offer such reduction. Effective suppression of excitation feedthrough requires various degrees of freedom (DOF) for adjusting geometrical positions, amplitudes, etc. In this work, a suitable MPI coil arrangement is presented. The adjustment process is based on the signals acquired by the receive chain and can be fully automated. The coil arrangement is realized as a scanner with a diameter of approximately 34 mm; one dimension is scanned electrically while full three dimensional scanning can be achieved via the mechanical DOFs by means of a robotic stage. Electrical characterization shows passive feedthrough suppression of more than 100 dB. First measurements of SPION samples are presented, showing improved signal
Assessing degradation of nano drug carriers - Magnetic particle imaging as a solution
No full textStimulus-triggered drug release by magnetic actuation of nano drug carriers is of high interest for targeted therapies. Most promising candidates are nano formulations based on biodegradable polymers and magnetic nanoparticles (MNP) because they have low side effects and customizable degradation properties. For the control drug release in vivo, monitoring of degradation dynamics play an important role. In this study, we demonstrate the feasibility of measuring degradation state of poly-(lactic-co-glycolic) acid magnetic nanoparticles (PLGA-MNP) using magnetic particle imaging (MPI). We show that due that the immobilization state of MNP during degradation leads to changes in image quality. Further, we test the influence of magnetic fluid hyperthermia on degradation of PLGA-MNP carriers and discuss the effects of degradation on MPI signal
A Novel Approach to FFL Trajectory Analysis
No full textThe sampling trajectory is an important parameter of a magnetic particle imaging (MPI) system and should be selected in order to guarantee the best image quality constrained by hardware limitations. A simulation study is performed with the side conditions of a permanent magnet-based field-free line (FFL) scanner system evaluating multiple trajectory types (radial, spiral, uniformspiral, flower) and trajectory densities in terms of spatial resolution. The findings provide information on suitable FFL trajectories and indicate initial trends for advantageous sampling patterns in the reference system. Within the used software framework, which has the potential to generate sequences based on real measurement data, we present here a novel approach to FFL trajectory analysis
Design of an In-Situ Magnetic Particle Spectrometer (INSPECT~II) for co-precipitation methodology-based synthesis
No full textMagnetic particle spectrometry (MPS) is a characterization tool, which helps in determining the magnetic properties of Magnetic nanoparticles (MNPs). MNPs heavily influence image resolution, hence intensive research is conducted to improve the magnetic properties of these MNPs. In-situ magnetic particle spectrometer (INSPECT) was first presented in 2019 and has the capability to track the nucleation and growth of MNPs. The presented research discusses the design and development of the second generation of INSPECT which investigates the impact of a fully controllable temperature bath, lower power requirements, and a new hybrid housing design for carrying out synthesis at higher temperatures. This research paper deals with the development of different hardware modules and sensitivity profiles of INSPECT II
Realtime iMPI-guided PTA with a lightweight human-sized MPI scanner
No full textBased on a novel open design implementing the so-called traveling wave MPI approach, the open interventional MPI (iMPI) system provides imaging of tracers based on superparamagnetic iron oxide nanoparticles (SPIONs) with high sensitivity, optimal patient handling and would even allow hybrid imaging of magnetic tracers within gold standard x-ray based interventional angiography systems. In initial experiments, the feasibility of a human-sized interventional MPI scanner with real-time data reconstruction and image visualization is demonstrated within a percutaneous transluminal angioplasty (PTA)