Radio Frequency Magnetic Field Research Articles

High-order magnetic resonance in the presence of strong longitudinal radio-frequency magnetic field based on atomic alignment states

High-order magnetic resonance in the presence of strong longitudinal radio-frequency magnetic field based on atomic alignment states

Anti-Proliferative Activity of Poloxamer Cobalt Ferrite Nanoparticles against Human Prostate Cancer (DU-145) Cells: In-Vitro Study

Prostate cancer is the second most frequent type of cancer death in men. This study refers to the novel hyperthermia application of poloxamer-coated cobalt ferrite as a new approach for thermal eradication of DU-145 human prostate cancerous cells under a radio frequency magnetic field (RF-MF). The hydrothermal method was applied for the synthesis of cobalt ferrite nanoparticles. Then, the structure, size, and morphology of nanoparticle were characterized. The cytotoxicity of the synthesized nanoparticles and RF-MF exposure on DU-145 prostate cancer cells was investigated separately or in combination with colony formation methods and MTT [3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide] assay. Transmission electron microscopy (TEM) confirmed the spherical morphology of nanoparticles with a size of 5.5 ± 2.6 nm. The temperature of cells treated with nanoparticles under RF-MF reached 42.73 ± 0.2°C after 15 min. RF-MF treatment or nanoparticles have not affected cell viability significantly. However, the combination of them eradicated 53% ± 4% of cancerous cells. In-vitro hyperthermia was performed on human prostate cancer cells (DU-145) with cobalt ferrite nanoparticles at specific concentrations that demonstrated a decrease in survival fraction based on colony formation assay compared to cells that were treated alone with nanoparticles or with RF-MF.

Machine Learning for the Design and the Simulation of Radiofrequency Magnetic Resonance Coils: Literature Review, Challenges, and Perspectives.

Radiofrequency (RF) coils for magnetic resonance imaging (MRI) applications serve to generate RF fields to excite the nuclei in the sample (transmit coil) and to pick up the RF signals emitted by the nuclei (receive coil). For the purpose of optimizing the image quality, the performance of RF coils has to be maximized. In particular, the transmit coil has to provide a homogeneous RF magnetic field, while the receive coil has to provide the highest signal-to-noise ratio (SNR). Thus, particular attention must be paid to the coil simulation and design phases, which can be performed with different computer simulation techniques. Being largely used in many sectors of engineering and sciences, machine learning (ML) is a promising method among the different emerging strategies for coil simulation and design. Starting from the applications of ML algorithms in MRI and a short description of the RF coil's performance parameters, this narrative review describes the applications of such techniques for the simulation and design of RF coils for MRI, by including deep learning (DL) and ML-based algorithms for solving electromagnetic problems.

MAPLE deposition of hybrid PLGA-Fe3O4- Cypress-PEDOT: PSS coatings

We report on the Matrix Assisted Pulsed Laser Evaporation, laser technology for depositing biocompatible, antimicrobial, hydrophilic, and biodegradable complex hybrid polymeric system loaded with essential cypress-oil and magnetite nanoparticles as resorbable implants, capable of targeting possible hyperthermia applications, an anticancer moderate field heating therapy. Magnetite nanoparticles based on iron oxide (Fe3O4) coated with Cypress essential oil (denoted: Fe3O4- Cypress) and embedded in PLGA (poly(lactic-co-glycolic acid) (denoted: PLGA-Fe3O4- Cypress-) and PLGA - poly(3,4-ethylene dioxythiophene) doped with poly(styrene sulfonate) anions) (PEDOT: PSS) mixture (denoted: PLGA-Fe3O4- Cypress- PEDOT: PSS) were used as MAPLE targets. The controlled drug delivery of the active Cypress oil, an antimicrobial therapeutic agent from Fe3O4- Cypress nanoparticles could be possible by applying an external radio frequency (RF) magnetic field. The Fe3O4-Cypress-based powders as well as the final hybrid coatings have been characterized in terms of stoichiometry, morphology, magnetic, antimicrobial properties, biocompatibility, and response to external physical stimuli. FTIR analyses confirmed the quasi-stoichiometric laser transfer of organic compounds while the XRD evidenced the semicrystalline structure of deposited thin films. SEM and AFM images evidence that conductive polymer addition led to the films' relief flattening and a decrease in the coatings' thickness and roughness by changing the polymeric packaging. The samples containing conductive polymer exhibited 3 times higher current and corrosion rate values. All coatings are hydrophilic and revealed enhanced cellular viability when cultured with osteoblast-like MG-63 cells. The composite structures exhibited significant antimicrobial activity against Gram-positive (Staphylococcus aureus), and Gram-negative (Escherichia coli) bacteria, as well as to the opportunistic yeast Candida albicans.

Scanning Spin Probe Based on Magnonic Vortex Quantum Cavities.

Performing nanoscale scanning electron paramagnetic resonance (EPR) requires three essential ingredients: First, a static magnetic field together with field gradients to Zeeman split the electronic energy levels with spatial resolution; second, a radio frequency (rf) magnetic field capable of inducing spin transitions; finally, a sensitive detection method to quantify the energy absorbed by spins. This is usually achieved by combining externally applied magnetic fields with inductive coils or cavities, fluorescent defects, or scanning probes. Here, we theoretically propose the realization of an EPR scanning sensor merging all three characteristics into a single device: the vortex core stabilized in ferromagnetic thin-film discs. On one hand, the vortex ground state generates a significant static magnetic field and field gradients. On the other hand, the precessional motion of the vortex core around its equilibrium position produces a circularly polarized oscillating magnetic field, which is enough to produce spin transitions. Finally, the spin-magnon coupling broadens the vortex gyrotropic frequency, suggesting a direct measure of the presence of unpaired electrons. Moreover, the vortex core can be displaced by simply using external magnetic fields of a few mT, enabling EPR scanning microscopy with large spatial resolution. Our numerical simulations show that, by using low damping magnets, it is theoretically possible to detect single spins located on the disc's surface. Vortex nanocavities could also attain strong coupling to individual spin molecular qubits with potential applications to mediate qubit-qubit interactions or to implement qubit readout protocols.

A model of radiofrequency and plasma coupling for compact ion sources and design

Inductive coupling of radiofrequency power to plasma is a complicate process, since it depends from the density of plasma itself, because ionization is a chain reaction process, and, at low density a capacitive coupling may mix with inductive coupling (with no Faraday screen). Plasma temperature Te , density ne and vector potential are closely coupled, giving nonlinear and singular systems of Partial Differential equations, which require slow iterative solutions, motivating the consideration of a 2D model, also as rapid design and first approximation tool. Plasma conductivity and heating depend on collision rate, which includes also the so-called stochastic collisions (mainly electron collisions with walls), proportionally more important at low gas density ng . Conductivity is also affected by static and radiofrequency magnetic fields; results for skin depth and stochastic collision estimates are reported. The transport of Te and ne inside source can be controlled by a magnetic filter B f . Considering a 5 cm radius H- ion source as example, solution of ne and Te are reported as a function of filter strength B fa, applied rf power and wall status; solver convergence methods andkey plasma observables are briefly discussed. Due to small dimension, a filter strength B fa in the order of 8 mT is needed to achieve electron temperature lower than 2 eV (for negative ion production) at extraction.

On the Evaluation of the Hyperthermic Efficiency of Magnetic Scaffolds.

Goal: Deep-seated tumors (DST) can be treated using thermoseeds exposed to a radiofrequency magnetic field for performing local interstitial hyperthermia treatment (HT). Several research efforts were oriented to the manufacturing of novel biocompatible magnetic nanostructured thermo-seeds, called magnetic scaffolds (MagS). Several iron-doped bioceramics or magnetic polymers in various formulations are available. However, the crucial evaluation of their heating potential has been carried out with significantly different, lab specific, variable experimental conditions and protocols often ignoring the several error sources and inaccuracies estimation. Methods: This work comments and provides a perspective analysis of an experimental protocol for the estimation methodology of the specific absorption rate (SAR) of MagS for DST HT. Numerical multiphysics simultions have been performed to outline the theoretical framework. After the in silico analysis, an experimental case is considered and tested. Results: From the simulations, we found that large overestimation in the SAR values can be found, due to the axial misplacement in the radiofrequency coil, while the radial misplacement has a lower impact on the estimated SAR value. Conclusions: The averaging of multiple temperature records is needed to reliably and effectively estimate the SAR of MagS for DST HT.

THE EFFECTS OF COMBINATION OF RADIOFREQUENCY AND PULSED MAGNETIC FIELD ON CAROTID ARTERIA ISCHEMIA AND REPERFUSION INDUCED BRAIN INJURY: A PRELIMINARY REPORT

Objective
 Cerebrovascular accident due to ischemia (IS)
 mediated by atherosclerotic plaque in the brain
 can trigger inflammation in the cerebral cortex,
 hippocampus and cerebellum tissues. Radiofrequency
 electromagnetic field (RF-EMF) and pulsed magnetic
 field (PMF) applications can increase nitric oxide
 formation from the vascular endothelial layer. The
 aim of this preliminary study is to reduce the damage
 caused by IS in different tissues of the brain by
 magnetic field applications.
 Material and Method
 A total of 9 rats, one rat in each group; sham,
 prophylactic RF, PMF, RF+PMF and therapeutic
 RF-EMF, PMF, RF-EMF+PMF, prophylactic and
 therapeutic RF-EMF+PMF and IS-only groups were
 distinguished. In single or combined applications of
 prophylactic/therapeutic RF-EMF and PMF groups,
 rats were taken to the experimental unit for 30
 minutes of magnetic field exposure before and after
 30 minutes of carotid artery occlusion for IS purposes.
 Histopathological hematoxylin-eosin staining in
 brain tissue (cerebral cortex and hippocampus)
 and cerebellum tissues taken after sacrification;
 With immunohistochemical analysis, brain derived
 neurotrophic factor (BDNF), tumor necrosis factoralpha
 (TNF-α), mammalian target of rapamycin
 (mTOR) and inducible nitric oxide synthase (iNOS)
 expressions were examined.
 Results
 Histopathologically significant hyperemia, edema,
 bleeding and neuronal degeneration were detected
 in the IS group. Additionally, immunohistochemically,
 an increase in TNF-α, mTOR, iNOS and a decrease
 in BDNF staining were observed. Prophylactic and/or
 therapeutic RF-EMF and/or PMF applications reversed
 all these parameters. The greatest improvement
 was observed in the Prophylactic+Therapeutic RFEMF+
 PMF group.
 Conclusion
 As a result, the regression of IS-related inflammation in
 both brain tissue parts and cerebellar tissues with RFEMF
 and PMF is important in terms of the formation
 of neurological deficits, the continuity of learning
 and memory mechanisms, and the preservation of
 balance functions.

Magnetic Field Intervention Enhances Cellular Migration Rates in Biological Scaffolds.

The impact of magnetic fields on cellular function is diverse but can be described at least in part by the radical pair mechanism (RPM), where magnetic field intervention alters reactive oxygen species (ROS) populations and downstream cellular signaling. Here, cellular migration within three-dimensional scaffolds was monitored in an applied oscillating 1.4 MHz radiofrequency (RF) magnetic field with an amplitude of 10 µT and a static 50 µT magnetic field. Given that cellular bioenergetics can be altered based on applied RF magnetic fields, this study focused on a magnetic field configuration that increased cellular respiration. Results suggest that RF accelerated cell clustering and elongation after 1 day, with increased levels of clustering and cellular linkage after 7 days. Cell distribution analysis within the scaffolds revealed that the clustering rate during the first day was increased nearly five times in the RF environment. Electron microscopy provided additional topological information and verified the development of fibrous networks, with a cell-derived matrix (CDM) visualized after 7 days in samples maintained in RF. This work demonstrates time-dependent cellular migration that may be influenced by quantum biology (QB) processes and downstream oxidative signaling, enhancing cellular migration behavior.

Carbonic anhydrase-magnetite nanocomposites with an RF field controlled enzymatic activity

A magnetic enzymatic composite was synthesized from non-toxic magnetite nanoparticles modified by biomimetic polymerization of modified dopamine and carbonic anhydrase enzyme, which has a significant role in neurodegenerative processes. The mass fraction of the enzyme in the composite was 10% wt, which corresponded to about 120 enzyme molecules per nanoparticle. The composite showed Km about 10 folds higher compared to free enzyme (0.22 and 0.019 mmol/L respectively) and Vmax four times lower (0.17 and 0.69 mmol/min). The enzymatic composite had 17% higher thermal stability compared to free enzyme and retained 95% of its initial activity after seven consecutive reuse cycles. In a colloidal state, the composite showed no response to the RF field due to the ballistic mechanism of heat dissipation but in concentrated form, the material showed up to 155% enhanced catalytic activity under the influence of heating radio frequency magnetic fields. The observed results are discussed and explained.

Reconstruction of the Electrical Properties in Human Bodies Based on the Estimation of the Unmeasurable Magnetic Fields

Electrical properties tomography (EPT) noninvasively reconstructs electrical properties (EPs) in human bodies from the radio-frequency magnetic field with magnetic resonance imaging. Although our previously proposed EPT method stably obtained EP distributions, EP reconstruction errors occurred because the unmeasurable magnetic field components were ignored. This study proposes a novel method to estimate the unmeasurable magnetic fields and to apply it to our previously reported EPT method. The results obtained from a numerical simulation and an experimental phantom indicate that the proposed estimation of the unmeasurable magnetic fields suppresses EP errors.

Resonating sub-wavelength metallic wires based pads for boosting signal-to-noise ratio of birdcage head coils at 1.5T MRI

Magnetic resonance imaging (MRI) is an increasingly popular non-invasive diagnostic imaging tool in modern healthcare. The signal-to-noise ratio (SNR) of MRI can be improved by locally enhancing radiofrequency (RF) magnetic field using metamaterials — without the need for stepping up static magnetic field strength. However, designing a thin and compact metamaterial-based structure for the most commonly used 1.5T MRI systems (operating at f0∼64MHz) remains highly challenging due to long vaccum wavelength λ0∼4.7m at resonance. The limited free space available inside MRI receive coil arrays (typically 10-20mm) restricts the practical usability of any bulky resonator (with dimensions in order of meters) inside commercial 1.5T MRI head transceiver-coils. In this paper, we design a thin and compact RF metamaterial-based pad comprising dual-layer wire-array resonators that fits in the available space and provides significant magnetic field enhancement at 1.5T MRI. The metamaterial-based pad provides the SNR enhancement by a factor of ∼19, on the surface of bio-model in contact with the pad, as compared to the case without pad while maintaining specific absorption rate well below the standard safety limit. We present an equivalent circuit approach combined with a transformer-based model to compute the SNR enhancement factor of metamaterial-based pad, which adequately explains the underlying physical mechanism of metamaterial’s magnetic resonance and closely estimates our numerical findings. We believe that, when integrated into the clinical 1.5T MRI systems, our proposed metamaterial-based pad can help improve the SNR of head MRI scans, resulting in either higher image quality or reduced scan time.

Characterizing current noise of commercial constant-current sources by using an optically pumped rubidium atomic magnetometer.

This paper introduces a method for characterizing the current noise of commercial constant-current sources (CCSs) using a free-induction-decay (FID) type optically pumped rubidium atomic magnetometer driven by a radio frequency magnetic field. We convert the sensitivity of the atomic magnetometer into the current noise of CCS by calibrating the coil constant. At the same time, the current noise characteristics of six typical commercial low-noise CCSs are compared. The current noise level of the Keysight model B2961A is the lowest among the six tested CCSs, which is 36.233 ± 0.022 nA/Hz1/2 at 1-25Hz and 133.905 ± 0.080 nA/Hz1/2 at 1-100Hz. The sensitivity of the atomic magnetometer is dependent on the current noise level of the CCS. The CCS with low noise is of great significance for high-sensitivity atomic magnetometers. This research provides an important reference for promoting the development of high precision CCS, metrology, and basic physics research.

Impact of weak radiofrequency and static magnetic fields on key signaling molecules, intracellular pH, membrane potential, and cell growth in HT-1080 fibrosarcoma cells

There are substantial concerns that extended exposures to weak radiofrequency (RF) fields can lead to adverse health effects. In this study, HT-1080 fibrosarcoma cells were simultaneously exposed to a static magnetic flux density between 10 mathrm{mu T} and 300 mathrm{mu T} and RF magnetic fields with amplitudes ranging from 1 nT to 1.5 μT in the frequency range from 1.8 to 7.2 MHz for four days. Cell growth rates, intracellular pH, hydrogen peroxide, peroxynitrite, membrane potential and mitochondrial calcium were measured. Results were dependent on carrier frequency and the magnitude of the RF magnetic field, modulation frequencies and the background static magnetic field (SMF). Iron sulphur (Fe-S) clusters are essential for the generation of reactive oxygen species and reactive nitrogen species (ROS and RNS). We believe the observed changes are associated with hyperfine couplings between the chemically active electrons and nuclear spins. Controlling external magnetic fields may have important clinical implications on aging, cancer, arthritis, and Alzheimer’s.

Self-sensing intelligent microrobots for noninvasive and wireless monitoring systems

Microrobots have garnered tremendous attention due to their small size, flexible movement, and potential for various in situ treatments. However, functional modification of microrobots has become crucial for their interaction with the environment, except for precise motion control. Here, a novel artificial intelligence (AI) microrobot is designed that can respond to changes in the external environment without an onboard energy supply and transmit signals wirelessly in real time. The AI microrobot can cooperate with external electromagnetic imaging equipment and enhance the local radiofrequency (RF) magnetic field to achieve a large penetration sensing depth and a high spatial resolution. The working ranges are determined by the structure of the sensor circuit, and the corresponding enhancement effect can be modulated by the conductivity and permittivity of the surrounding environment, reaching ~560 times at most. Under the control of an external magnetic field, the magnetic tail can actuate the microrobotic agent to move accurately, with great potential to realize in situ monitoring in different places in the human body, almost noninvasively, especially around potential diseases, which is of great significance for early disease discovery and accurate diagnosis. In addition, the compatible fabrication process can produce swarms of functional microrobots. The findings highlight the feasibility of the self-sensing AI microrobots for the development of in situ diagnosis or even treatment according to sensing signals.

Weak Radiofrequency Field Effects on Chemical Parameters That Characterize Oxidative Stress in Human Fibrosarcoma and Fibroblast Cells.

In the last few decades, evidence has surfaced that weak radiofrequency (RF) fields can influence biological systems. This work aims to improve our understanding of how externally applied weak RF fields alter concentrations of chemical parameters that characterize oxidative stress. We conducted a series of experiments to investigate the effects of applying weak RF magnetic fields within the 3-5 MHz region on mitochondrial respiration in both human fibrosarcoma and fibroblast cells over a period of four days. Our experimental data show that RF fields between 3 and 5 MHz were able to change the modulation of mitochondrial signaling by changing the cell growth, mitochondrial mass, and oxidative stress. Exposure to RF fields at 4.2 MHz significantly increased the mitochondrial mass and oxidative stress in fibrosarcoma cells. There are substantial concerns that extended exposure to weak RF fields can lead to health effects. The ability to control these parameters by external magnetic fields may have important clinical implications.

Chaos control of fractional order nonlinear Bloch equation by utilizing sliding mode controller

Nuclear magnetic resonance is commonly used in engineering, chemistry, and medicine to study complex materials by relating magnetization to applied radiofrequency, gradient, and static magnetic fields through the Bloch equation. Chaos in the Bloch equation is a key factor in many important applications. This study focuses on the study of the Bloch equation under the influence of the Caputo fractional derivative, both with and without delay, and explores the underlying chaos using a sliding mode controller. The controller’s effectiveness is observed under uncertainty and external disturbances for both commensurate and incommensurate systems, and theoretical aspects such as the existence and uniqueness of solutions and the stability of the controlled system are examined. Lyapunov exponents are calculated for various fractional derivatives to demonstrate the presence of chaos in the system, and numerical simulations are used to verify theoretical assertions.

Nuclear quadrupole resonance spectroscopy with a femtotesla diamond magnetometer.

Radio frequency (RF) magnetometers based on nitrogen vacancy centers in diamond are predicted to offer femtotesla sensitivity, but previous experiments were limited to the picotesla level. We demonstrate a femtotesla RF magnetometer using a diamond membrane inserted between ferrite flux concentrators. The device provides ~300-fold amplitude enhancement for RF magnetic fields from 70 kHz to 3.6 MHz, and the sensitivity reaches ~70 fT√s at 0.35 MHz. The sensor detected the 3.6-MHz nuclear quadrupole resonance (NQR) of room-temperature sodium nitrite powder. The sensor's recovery time after an RF pulse is ~35 μs, limited by the excitation coil's ring-down time. The sodium-nitrite NQR frequency shifts with temperature as -1.00±0.02 kHz/K, the magnetization dephasing time is T2*=887±51 μs, and multipulse sequences extend the signal lifetime to 332±23 ms, all consistent with coil-based studies. Our results expand the sensitivity frontier of diamond magnetometers to the femtotesla range, with potential applications in security, medical imaging, and materials science.

Biot–Savart-Based Design and Workbench Validation at 100 MHz of Transverse Field Surface RF Coils

Radiofrequency (RF) surface coils are extensively used as receivers in magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) systems thanks to their high signal-to-noise ratio (SNR). For specific magnetic resonance applications, the design of dedicated RF surface coils with a transverse (to the coil’s plane) RF magnetic field pattern can be necessary. Such transverse-field RF coils are constituted by several central linear (parallel or crossing) conductor elements connected by return current paths. Typically, the outer shape of such RF coils is circular or squared, although other geometries can be used. This paper describes the implementation and validation of a transverse-field RF surface coil simulator based on magnetostatic analysis, which permits the design and optimization of square butterfly and figure-of-eight RF coils with adjustable size and mutual distance between the central linear current elements. The simulation results, compared with the ones provided by a standard square loop RF coil, were validated with 100 MHz workbench measurements performed on three home-built prototypes. Finally, two novel quadrature RF coil structures designed by overlapping two orthogonal square butterfly and figure-of-eight RF coils were simulated and theoretically characterized. The RF coils described here should be suitable for a wide range of MRI/MRS preclinical/clinical applications, mainly at fields below 3 T.

Study of protein encapsulated manganite nanoparticles for magnetic Hyperthermia

Used in the past as an efficient drug-delivery carrier, the natural protein Bovine Serum Albumin (BSA) has been tried in the present study to coat Lanthanum Strontium Manganese Oxide (LSMO) nanoparticles (NPs) called manganite, for magnetic Hyperthermia applications. LSMO NPs generate heat when subjected to a radiofrequency magnetic field and as a novel attempt; they were functionalized with BSA by its “denaturation” at 80°C. This was done to probe the effect of protein bonding with nanoparticles by “unfold” of its molecular structure and to enhance the biocompatibility of LSMO. Presence of BSA on NPs was assessed through electron microscopy (HRTEM), Fourier transform (IR) spectroscopy and thermogravimetric analysis (TGA); that showed successful outcomes. The magnetization was analyzed by super quantum interface device (SQUID). For Hyperthermia studies, BSA coated NPs were dispersed in phosphate buffer saline and attained an appreciable specific absorption rate of 126.9 W/g showing their potential for future applications.