AI Article Synopsis
- MR Current Density Imaging (MRCDI) measures magnetic field changes from weak current injection in the head, but stray fields can interfere significantly with accurate measurements.
- The study validated a new MRCDI method with a low noise floor and examined the effects of cable currents and stray fields on the accuracy of current flow reconstructions under different experimental conditions.
- Results indicate that while cable correction is effective, physiological noise and minor patient movements can still impact measurements, highlighting the need for precise field correction in MRCDI.
Article Abstract
Purpose: MR Current Density Imaging (MRCDI) involves weak current-injection into the head. The resulting magnetic field changes are measured by MRI. Stray fields pose major challenges since these can dominate the fields caused by tissue currents. We analyze the sources and influences of stray fields.
Methods: First, we supply validation data for a recently introduced MRCDI method with an unprecedented noise floor of ∼0.1 nT in vivo. Second, we assess the accuracy limit of the method and our corresponding cable current correction in phantoms ensuring high signal-to-noise ratio (SNR). Third, we simulate the influence of stray fields on current flow reconstructions for various realistic experimental set-ups. Fourth, we experimentally determine the physiological field variations. Finally, we explore the consequences of head positioning in an exemplary head coil, since off-center positioning provides space for limiting cable-induced fields.
Results: The cable correction method performs well except near the cables. Unless correcting for cable currents, the reconstructed current flow is easily misestimated by up to 45% for a realistic experimental set-up. Stray fields dominating the fields caused by tissue currents can occur, e.g. due to a wire segment 20 cm away from the imaged region, or due to a slight cable misalignment of 3°. The noise is increased by 40% due to physiological factors. Minor patient movements can cause field changes of ∼40 nT. Off-centered head positioning can locally reduce SNR by e.g. 30%.
Conclusions: Quantification of stray fields showed that MRCDI requires careful field correction. After cable correction, physiological noise is a limiting factor.
Download full-text PDF |
Source |
|---|---|
| http://dx.doi.org/10.1016/j.ejmp.2019.02.022 | DOI Listing |
Publication Analysis
Top Keywords
Similar Publications
Simulation of the charged particle deflection from the sweeping magnet array in the Lunar Environment heliospheric X-ray imager.
Rev Sci Instrum
December 2024
662, NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA.
Article Synopsis
- The Lunar Environment heliospheric X-ray Imager (LEXI) is designed to capture x-ray images from solar wind interactions in Earth's magnetosheath, helping researchers understand energy transfer into Earth's magnetosphere.
- As part of a lunar lander mission landing in Mare Crisium, LEXI features a unique array of 48 neodymium magnets to protect against interference from charged particles while minimizing stray magnetic fields.
- A Runge-Kutta-based simulation model shows that LEXI's deflector array and other particle suppression methods effectively limit proton and electron contamination, ensuring the success of its imaging capabilities and offering insights for similar instruments.
Article Synopsis
- * Researchers used a specialized magnetic microscope to image the magnetic fields from many isolated SPIONs, discovering distinct magnetization patterns that traditional methods wouldn't reveal.
- * The study also recorded SPION relaxation times after an applied magnetic field was turned off, showing a wide range of characteristics among the nanoparticles, indicating their varied behavior and potential for further nanomagnetism research.
High-Performance Telescope System Design for Space-Based Gravitational Waves Detection.
Sensors (Basel)
November 2024
MOE Key Laboratory of Fundamental Physical Quantities Measurement and Hubei Key Laboratory of Gravitation and Quantum Physics, PGMF and School of Physics, Huazhong University of Science and Technology, Wuhan 430074, China.
Article Synopsis
- Space-based gravitational wave (GW) detection utilizes the Michelson interferometry principle to create long baseline laser interferometers capable of sensing signals within a frequency range of 10-1 Hz.
- The paper introduces an advanced design using an off-axis four-mirror configuration that minimizes wavefront aberration and enhances stray light suppression, addressing background noise issues.
- This improved design achieves a wavefront error of less than λ/500 in the main field of view and can reach an error of less than λ/30 with a 92% probability, making it a strong candidate for future GW detection projects.
Nearly perfect spin polarization of noncollinear antiferromagnets.
Nat Commun
November 2024
Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, 68588-0299, USA.
Ferromagnets with high spin polarization are known to be valuable for spintronics-a research field that exploits the spin degree of freedom in information technologies. Recently, antiferromagnets have emerged as promising alternative materials for spintronics due to their stability against magnetic perturbations, absence of stray fields, and ultrafast dynamics. For antiferromagnets, however, the concept of spin polarization and its relevance to the measured electrical response are elusive due to nominally zero net magnetization.
View Article and Find Full Text PDFA compact and mobile stray-field NMR sensor.
J Magn Reson
December 2024
Institute of Smart Sensors, University of Stuttgart, Stuttgart, Germany; Center for Integrated Quantum Science and Technology (IQ(ST),), Stuttgart, Germany; Institute for Microelectronics Stuttgart (IMS CHIPS), Stuttgart, Germany.
In this paper, we introduce a compact, single-sided stray field sensor for NMR relaxometry applications. The sensor consists of four main components: the magnet, the RF coil, the spectrometer, and the translation stage. Our proposed magnet, an improved design of the Profile NMR-MOUSE, is designed for low weight, compactness, and magnetic field homogeneity, achieved through various shim strategies using a mixed genetic algorithm.
View Article and Find Full Text PDFWant AI Summaries of new PubMed Abstracts delivered to your In-box?
Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!