Applied Magnetic Resonance最新文献

In this study, the Electron Spin Resonance (ESR) dosimetric potential of surgical face masks was investigated within the intermediate gamma dose range of 0.05–10 kGy. White, blue, and green mask samples were used for this analysis. FTIR and XRD analyses confirmed that all masks were made of polypropylene. No ESR signals were detected in the unirradiated masks. However, in gamma-irradiated samples, resonance signal components at ({g}_{parallel }= 2.031 pm 0.002) and ({g}_{perp }= 2.007 pm 0.002), associated with peroxy radicals (RO2·), were observed, with the intensity of the ({g}_{perp }= 2.007 pm 0.002) signal increasing exponentially within the investigated dose range. Despite the decrease in radiation-induced signal intensities at room temperature, surgical masks can be considered as emergency dosimeters when other materials suitable for dose estimation are unavailable.

For a doctor to diagnose a patient and conduct quantitative analysis, medical images must be accurately registered. Deep learning-based image registration methods have been explored extensively, but accurate registration of medical images still remains a major concern. To address the issue of accurate alignment in medical images, this paper presents an approach employing unsupervised learning algorithm U-shaped convolution neural network (U-Net) model, followed by teaching learning-based optimization (TLBO) along with affine transformation for grayscale as well as colored medical image registration. The combined two-channel image generated using moving and fixed image is given as an input to encoder and decoder phase of U-Net model to learn image features and generate displacement field. To predict the spatial transformation parameters, a set of control points are generated to define the deformation field and moving image feature to produce the warped image. To improve the quality of warped image, TLBO with rigid transformation parameter (RTP) on fixed and U-Net warped image is applied by detecting the optimum value of transformation parameters. The proposed approach is implemented and evaluated using five different datasets for 2D and 3D monomodal medical MR and CT image modalities as well as multimodal clinical datasets. For 3D representation, transfer learning is used to obtain the warped images using the 3D pre-trained weights of VoxelMorph U-Net model. In comparison to state-of-the-art approaches like symmetric image normalization (SyN) and VoxelMorph, the Dice score value increases from 0.742 as reported by Balakrishnan (Proceedings of the IEEE Computer Society Conference on Computer Vision and Pattern Recognition, 2018) to 0.9542 and 0.710 as reported by Zhou (IEEE 18th International Symposium on Biomedical Imaging (ISBI), 2021) to 0.9024, while the Hausdorff distance decreases from 2.0521 Zhang (Appl Intell 12:1-18) to 1.5607 and 2.0446 Zhang (Appl Intell 12:1-18) to 1.0923, respectively, for deformable medical image registration under different image modalities. Higher value of Dice score and lower value of Hausdorff distance with our proposed approach in similarity metrics indicates better registration accuracy.

The Griffiths phase forms in various magnetics in the presence of disorder and spin fluctuations in the system. In this paper, we present experimental facts in which the Griffiths phase is observed from the temperature dependence of magnetization, EPR, and SANS spectra; we present an equation describing the anisotropy fields, which are actually found from the EPR angular dependence of the resonance magnetic field and a formula for determining the critical exponent for magnetizations description. The features of the observation of the Griffiths phase in lanthanum manganites are presented.

The current study aimed to investigate the feasibility of using the pseudo-blood^®, adjusted to equal specific gravity of beads and solution, as a phantom for diffusion-weighted imaging (DWI) evaluation. The pseudo-blood^® with bead concentrations was adjusted to 0%, 9.8%, 28.1%, and 48.5% and was used as phantoms. Approximately 3-min of DWI was performed 15 times at 10-min intervals. The same experiment was conducted after 30, 60, and 90 days. The coefficients of variation of the obtained intra- and inter-day apparent diffusion coefficient (ADC) values were calculated. The ADC values significantly decreased with increasing bead concentrations in the pseudo-blood^®, with ADC values of 0.789 ± 0.002, 0.753 ± 0.001, 0.709 ± 0.003, and 0.685 ± 0.003 × 10⁻³ mm² s⁻¹ at bead concentrations of 0%, 9.8%, 28.1%, and 48.5% (Day 0), respectively. The intra- and inter-day coefficients of variation and repeatability coefficient were < 5% and < 5 × 10⁻⁵ mm² s⁻¹ for all phantoms. Therefore, the pseudo-blood^® can be used as a phantom for DWI evaluation.

Oxidative stress has been found to burden dialysis patients relying on artificial kidney membranes. If the artificial kidney membrane itself had a higher antioxidant capacity, scavenging the reactive oxygen species generated during dialysis may be possible. However, no means to compare the antioxidant capacity of the membranes is currently available. Therefore, we developed a continuous-flow spin-trapping electron spin resonance (CFST-ESR) method to evaluate the superoxide radical (O₂^·–) scavenging capacity of artificial kidney membranes. In the flow-system of the CFST-ESR, O₂^·– was constantly produced on the membrane surface through the riboflavin dependent photo-reduction of solvated oxygen, and the resulted O₂^·– was quantitatively detected as DMPO (5,5-dimethylpyrroline-N-oxide) spin-adduct radical (DMPO/O₂). Comparison of ESR signal intensity of DMPO/O₂ provide information regarding the O₂^·– eliminating capacity of polysulfone made kidney membranes (PFs). Based on the results of CFST-ESR measurements conducted for standard and vitamin E coated PFs, the latter vitamin E coated PFs membrane exhibit a higher O₂^·– scavenging capacity than that of the standard one. The newly developed CFST-ESR method can provide guidelines for the development of an artificial kidney membrane that can reduce oxidative stress caused by dialysis, considering the modification of PFs membranes by antioxidants other than vitamin E.

Nuclear magnetic resonance (NMR) spin–spin T₂ relaxation is applied to characterize structural rearrangements in solid–solid phase transitions of lipids. 1D T₂ relaxation distributions as a function of temperature indicate solid–solid transitions not easily discernible by differential scanning calorimetry (DSC). T₂–T₂ correlation exchange measurements are demonstrated to be sensitive to spin-diffusion, allowing measurement of morphological length scales related to solid–solid molecular structure rearrangement by NMR relaxometry. T₂ dispersion distributions indicate radio frequency pulse separation time dependence which alters with morphology and temperature. The NMR relaxometry data are complementary to DSC and has potential for bench top low field NMR implementation.

Copper (II) interaction and ion-exchange kinetics with dimethylamine (PA-1), trimethylamine (PA-2), pyridine (PA-3), phosphonoamine (PA-4), ethylene diamine phosphonic (PA-5, PA-6, PA-7), diethylamine (PA-8) ampholytes and phosphonic acid cationite CMF were investigated. In PA-1, PA-2, PA-3, PA-4, and PA-8, ethylene diamine phosphonic ampholytes (PA-5, PA-6, PA-7) and phosphonic acid cationite CMF Cu(R-HPO₃)₂(H₂O)₄ (A) and aqua complexes [Cu (H₂O)₆]²⁺are forming. The ampholyte polymer matrix structure consists of two packaging density segments. In the first place copper, (II) occupy high density region with a low water content where complex structure is Cu(R-HPO₃)₂(H₂O)₄. The self-diffusion coefficient of Cu²⁺ calculated on the basis of EPR spectra analysis is in agreement with self-diffusion coefficient measured by radioactive-tracer technique. In ethylene diamine phosphonic polyampholytes PA-5, PA-6, PA-7 copper (II) forms stable complexes with amino group nitrogen atoms containing 4 (D) or 2 nitrogen atoms (E). In PA-5, PA-7 complexes with 2 and 4 nitrogen atoms and Cu(R-HPO₃)₂(H₂O)₄ are formed. In PA-6, isotropic line F appeared, which belongs to E complexes where Cu²⁺ is exchange coupled to each other. In PA-7, EPR spectra consist of line A, line E and isotropic line G of copper (II) aqua complexes. Such multiversity of copper (II) complexes is due to these polyampholytes’ chemical inhomogeneity. Copper (II) sorption and desorption kinetics depending on outer aqueous solution concentration (CuSO₄ or HCl) and ampholyte grain diameters were investigated. Desorption kinetic curves are approximated by external diffusion and diffusion with moving boundary mechanisms.

Magnetic Resonance Imaging (MRI) is a crucial tool in medical diagnostics, yet reconstructing high-quality images from under-sampled k-space data poses significant challenges. This study introduces Federated Adversarial MRI Enhancement (FAME), a novel framework combining Federated Learning (FL) with Generative Adversarial Networks (GANs) to enhance MRI reconstruction while maintaining patient privacy. FAME utilizes a hybrid model aggregation strategy that dynamically weights updates from local generators, ensuring a balanced contribution based on dataset size and quality. Each local generator is trained on-site-specific data, while a global discriminator evaluates and refines the aggregated updates to improve image quality. FAME addresses key issues in medical imaging, including data privacy, model generalization, and robustness, by integrating advanced GAN architectures such as multi-scale convolutions, attention mechanisms, and Graph Neural Networks (GNNs). Differential privacy and secure aggregation protocols are implemented to protect sensitive data during training. Extensive experiments using the fastMRI Brain and Knee datasets, along with the BraTS 2020 and IXI dataset, show that FAME outperforms existing models, achieving superior PSNR and SSIM values. This decentralized framework offers scalable, privacy-preserving MRI reconstruction, making it a promising solution for diverse clinical applications.

When cooled, some manganites of the general form RE_1-xA_xMn³⁺_1-xMn⁴⁺_xO₃ where RE is a trivalent rare earth or Bi³⁺ ion and A is a divalent alkaline earth ion, undergo a ‘charge ordering’ (CO) transition resulting in a periodic ‘ordered’ arrangement of the Mn³⁺ and Mn⁴⁺ ions in the crystal lattice leading to an increase in the resistivity and antiferromagnetic ordering. Size reduction to nanoscale is an intrinsic way of destabilizing CO for achieving properties, such as room temperature colossal magnetoresistance, important for applications. Here, we address the still unsettled question in this context of whether this size induced ‘melting’ of CO in manganites is complete or if some charge order persists at short range, through comprehensive electron paramagnetic resonance (EPR) and magnetic studies of nanoparticles of Sm_0.42Ca_0.58MnO₃ and those of the bulk counterpart for comparison. The nanosized samples were prepared by microwave assisted reverse micelle method by optimizing the choice of the surfactant as well as the water to surfactant ratio to obtain particles of minimum size and polydispersity. The crystallite and particle sizes were estimated by X-ray diffraction and transmission electron microscopy. The valence states of the manganese ions on the surface of the particles were determined by X-ray photoemission spectroscopy. The near-total absence of the tell-tale signatures of CO viz. the peaks in magnetization and EPR intensity and the minimum in the EPR linewidth at the CO temperature T_CO point towards a complete disappearance of charge order in sufficiently small and monodisperse nanomanganites.