Search Results (61)

Animal studies show that sleep regulation depends on subcortical networks, but whether the connectivity between subcortical areas contributes to human sleep variability remains unclear. We investigated whether the effective connectivity between the LC and hypothalamic subparts during wakefulness relates to sleep electrophysiology. Thirty-three younger (~22 y, 27 women) and 18 late middle-aged (~61 y, 14 women) healthy individuals underwent 7-Tesla functional MRI during wakefulness to assess LC–hypothalamus effective connectivity. Additionally, sleep EEG was recorded at night in the lab to examine the relationships between effective connectivity measures and REM sleep theta energy as well as sigma power prior to REM. Connectivity analyses revealed strong mutual positive influences between the LC and both the anterior–superior and posterior hypothalamus, consistent with animal studies. Aging was negatively associated with the connectivity from the anterior–superior hypothalamus (including the preoptic area) to the LC. In late middle-aged adults, but not younger adults, stronger effective connectivity from the anterior–superior hypothalamus to the LC was associated with lower REM theta energy. This association extended to other low-frequency bands during REM and NREM sleep. These findings highlight the age-dependent modulation of LC–hypothalamus interactions and their potential roles in sleep regulation, providing new insights into neural mechanisms underlying age-related sleep changes. Full article

Purpose: To analyze the structural changes in the brain related to combined hearing and vision loss in patients with Usher syndrome (USH) obtained by 7 Tesla MRI. Methods: Twenty patients with a diagnosis of USH and fifteen normal age- and gender-matched subjects were included in this study. USH patients underwent ophthalmological examination. All subjects underwent 7 Tesla MRI of the brain in two sequences: 3D BRAVO T1-weighted and 3D MT-weighted SILENT sequence. Results: Mean values of LGN volumes (right 95.65 mm³, left 88.61 mm³) are significantly (p < 0.001) lower in the USH group than in the control group (right 126.64 mm³, left 120.37 mm³). The average volumes of the left cuneus (4102.85 mm³), right parsorbitalis (2133.95 mm³), and right rostralanteriorcingulate cortex (ACC) (1727.60 mm³) in the patient group are significantly (p = 0.03673, 0.02434, and 0.04204, respectively) lower than in the control group (4673.73 mm³, 2485.13 mm³, and 2060.00 mm³, respectively). Mean lengths of the left lingual cortex (1.99 mm) and right pericalcarine cortex (1.84 mm) in the patient group are significantly (p = 0.02449 and 0.03153, respectively) smaller than in the control group (2.09 mm and 2.0 mm, respectively). Average lengths of the right insula (2.74 mm) in the patient group are significantly (p = 0.00041) greater than in the control group (2.49 mm). Conclusions: Parts of the brain engaged in the visual processing as LGN, pericalcarine cortex, lingual gyrus, and cuneus, are decreased, as well as those involved in hearing and language processing, such as parsorbitalis and ACC. The insula, a higher-order brain area possessing a crucial role in olfactory processing, is increased in USH patients. Our findings enhance the understanding of structural brain abnormalities related to combined hearing and vision loss and suggest complex adaptive changes that should be considered in the development of new visual rehabilitation and restitution strategies in USH patients. Full article

Background/Objectives: To quantitatively assess lateral geniculate nucleus (LGN) volume using 7 Tesla MRI in patients with Stargardt disease (STGD). Methods: A total of 18 patients with STGD and 15 healthy volunteers were examined with a 7 Tesla MRI of the brain. Measures of LGN volume were performed manually by three independent investigators (radiologists) using ITK-SNAP software, version 4.0.0-rc.2. The volume of the thalamus was evaluated using the open-source automated software package FreeSurfer. Before 7 Tesla MRI, patients underwent ophthalmic examination and 1.5 Tesla MRI. Results: The average LGN volume in both hemispheres was significantly smaller in patients with STGD (right, −111.2 mm³; left, 107.4 mm³) than in the control group (right, −128.7 mm³; left, 123.6 mm³, respectively) (p < 0.0001). The ratio of LGN to thalamus in the right hemisphere was significantly lower (p = 0.024) in the group of patients with STGD (0.014) than in the control group (0.017). Conclusions: The right and left LGN volumes in MR 7T imaging, as well as the right LGN/thalamus ratio, were reduced in patients with STGD compared to controls. 7T MRI using the 3D MT-weighted SILENT protocol provides new insight into structural changes in the brain in retinal dystrophies and offers a possible marker of the response to future therapies in STGD. Full article

Objectives: Methamphetamine (MA) abuse during adolescence can have a significant impact on brain development. On the other hand, regular exercise is known to promote brain health and may have neuroprotective effects. The purpose of this study is to compare brain volumes in three different adolescent groups: those with active methamphetamine use disorder (MUD), adolescent athletes who regularly exercise, and healthy control adolescents. Methods: This MRI study involved three groups of adolescents: 10 with active MUD (9 males, 1 female), nine licensed runner adolescents (three males, six females), and 10 healthy adolescents (5 males, 5 females). Brain volumes were analyzed using T1-weighted images from a 3.0 Tesla MRI scanner, and then segmented automatically with vol2Brain. Statistical analyses included ANCOVA with sex as a covariate and LSD post hoc tests performed using SPSS Statistics 23. Results: Adolescents with MUD showed a 10% increase in total white matter volume compared to the athlete group. Conversely, cortical gray matter volume was reduced by 4% compared to the healthy control group and by 7% compared to the athlete group. The frontal and insular cortices in the MUD group had significantly diminished volumes compared to the athlete group. Overall, individuals with MUD had decreased gray matter volumes and increased white matter volumes in their brains. The brain volumetric differences between the MUD group and the athlete group were statistically significant. Conclusions: The brains of those with MUD displayed a reduction in gray matter volume and an increase in white matter volume, indicating damage from MA on the developing adolescent brain. The volumetric disparities between the MUD and athlete groups were found to be significantly different, suggesting a possible neuroprotective factor of exercise. Further studies are required to explore the potential of exercise-based interventions in alleviating the harmful effects of MA abuse. Full article

Rhizopus stolonifer causes soft rot disease in strawberry and is considered one of the most destructive pathogens affecting strawberries worldwide. This study investigated the efficacy of three atmospheric non-thermal plasmas (NTPs) consisting of gliding arc (GA), Tesla coil (TC) and dielectric barrier discharge (DBD) for controlling R. stolonifer infection. Fungal mycelial discs were exposed to these plasmas for 10, 15 or 20 min, whereas conidial suspensions were treated for 1, 3, 5 or 7 min. Morphological alterations following non-thermal plasma exposure were studied using scanning electron microscopy (SEM). Exposure to GA and DBD plasmas for 20 min completely inhibited mycelial growth. SEM analysis revealed significant structural damage to the mycelium, sporangia and sporangiospores of treated samples compared to untreated controls. Complete inhibition of sporangiospore germination was achieved with treatments for at least 3 min for all NTPs. Pathogenicity assays on strawberry fruit showed that 15 min exposure to any of the tested NTPs completely prevented the development of soft rot disease. Importantly, NTP treatments did not adversely affect the external or internal characteristics of treated strawberries. These findings suggest that atmospheric non-thermal plasmas offer an effective approach for controlling R. stolonifer infection in strawberries, potentially providing a non-chemical alternative for post-harvest disease management. Full article

In this study, the effect of aging heat treatment on the superelastic properties and microstructure of [001]-oriented Fe₄₁Ni₂₈Co₁₇Al_11.5Ti_1.25Nb_1.25 (at.%) single crystals was investigated using the cyclic superelastic strain test and a transmission electron microscope (TEM). The TEM results reveal that the average precipitate size is around 3–5 nm in the 600 °C/24 h samples, 6–8 nm in the 600 °C/48 h samples, and 10–12 nm in the 600 °C/72 h samples. The results indicate that precipitate size increases as aging time increases from 24 to 72 h. EDS analysis results show decreased Fe and increased Ni when the analyzed line crosses the precipitate region. The diffraction pattern results show that the precipitate has an L1₂ crystal structure. The thermo-magnetization curves of single crystals under the three aging conditions (600 °C/24 h, 600 °C/48 h, and 600 °C/72 h) show that the values of the transformation temperatures increased from 24 to 72 h. Magnetization was saturated at 140 emu/g under the magnetic field of 7 Tesla. When increasing the magnetic field from 0.05 to 7 Tesla, the transformation temperatures rose. The results indicate that magnetic fields can activate martensitic transformation. From the results of the superelasticity test at room temperature, [001]-oriented FeNiCoAlTiNb single crystals aged at 600 °C for 24, 48, and 72 h presented recoverable strains of 3%, 5.1%, and 2.6%, respectively. Digital image correlation (DIC) results of the aged samples show that two martensite variants were activated during the superelasticity test. The two variants form corresponding variant pairs (CVPs) and improve the recoverable strain of superelasticity. Although maximum recoverable strain was obtained for the 600 °C/48 h samples, the samples show poor cyclic stability at room temperature after applying the 6% strain. According to the DIC results, the retained martensite, which is pinned by dislocations, was observed after the test. The irrecoverable strain was attributed to the residual martensite. For the 600 °C/72 h samples, the large size of the precipitates poses an obstacle to dislocation transformation and formation. The dislocations increase the stress hysteresis width and stabilize the martensite, causing poor recoverability. Full article

Background: Post-sepsis cardiomyopathy is associated with an increased risk of adverse cardiovascular outcomes. It remains poorly understood, which limits therapeutic development. This study characterised post-sepsis cardiomyopathy using cardiovascular magnetic resonance (CMR) imaging. Methods: Patients admitted with acute sepsis and suspected cardiac injury or heart failure who subsequently (47 days [IQR: 22–122]) underwent CMR at a UK tertiary cardiac centre were included. Age- and gender-matched controls (n = 16) were also included. Subjects underwent CMR at 1.5 Tesla with cines, native T1- and T2-mapping, and late gadolinium enhancement (LGE) imaging. Results: Of the 22 post-sepsis patients (age 50 ± 13 years; 64% males), 13 patients (59%) had left ventricular (LV) dilatation. Patients had significantly elevated left ventricular (LV) end-diastolic and end-systolic volume indices compared to controls (p = 0.011 and p = 0.013, respectively). Eleven patients (50%) had LV systolic dysfunction (ejection fraction < 50%), most of whom (8/11) had non-ischaemic patterns of LGE (n = 7 mid-wall; n = 1 mid-wall/patchy). In the eleven patients with preserved LV systolic function (ejection fraction ≥ 50%), three patients (27%) had significant LGE (n = 1 mid-wall; n = 1 subepicardial/mid-wall; n = 1 patchy). Compared to controls, patients had elevated septal native myocardial T1 values (p < 0.001) but similar septal native myocardial T2 values (p = 0.090), suggesting the presence of myocardial fibrosis without significant oedema. Conclusions: Post-sepsis cardiomyopathy is characterised by LV dilatation, systolic dysfunction, and myocardial fibrosis in a non-ischaemic distribution. Significant myocardial oedema is not prominent several weeks post-recovery. Further work is needed to test these findings on a multi-centre basis and to develop novel therapies for post-sepsis cardiomyopathy. Full article

Objectives: The purpose was to quantitatively examine brain structures using 7 Tesla MRI in the presence of visual loss caused by retinitis pigmentosa (RP) related to retinitis pigmentosa GTPase regulator (RPGR) gene pathogenic variants. Methods: Twelve male patients with RP (mean visual acuity 0.4) related to confirmed RPGR pathogenic variants and fifteen healthy volunteers were examined with 7 Tesla MRI of the brain. Measures of the lateral geniculate nucleus (LGN) volume were performed manually by three independent investigators (radiologists) using ITK-SNAP (Insight Segmentation and Registration Toolkit) software. Other brain structures were evaluated using the open-source automated software package FreeSurfer. Prior to the 7 Tesla MRI, patients underwent an ophthalmic examination and a 1.5 Tesla MRI. Results: The mean LGN volume (right—100 mm³, left—96 mm³) and left lingual gyrus volume (6162 mm³) were significantly lower in RPGR patients in comparison to the control group (129 mm³, 125 mm³, and 7310 mm³, respectively), whilst some brain regions related to other sensory information such as the left isthmus cingulate (3690 mm³) and entorhinal cortex (right—1564 mm³, left 1734 mm³) were significantly or almost significantly higher in the RPGR group than in the control group (2682 mm³, 960 mm³, and 1030 mm³, respectively). Moreover, compared to the control group, the RPGR group’s thalamus-to-LGN ratio was substantially higher. Conclusions: The use of the 7 Tesla MRI revealed numerous structural abnormalities of the visual pathway in patients with RPGR-related RP. The reorganization of the structures of the brain demonstrated in patients with RPGR-related RP reveals a certain degree of plasticity in response to visual loss. These findings may help improve diagnostic and therapeutic strategies for RP patients and contribute to the development of precision medicine. Full article

Although the stifle joint of wild felines shares several characteristics observed in domestic cats, other characteristics are specific to each species. This study aimed to evaluate the stifle joints of eight Puma concolor, including two young and six adults, through different imaging examinations. All stifles were assessed using radiographs and computed tomography (CT). Magnetic resonance imaging (MRI) was performed on the stifles of one animal using 7 Tesla equipment. In all imaging modalities, the four sesamoid bones were detected. Meniscal mineralization was identified in the stifles of three adult animals and one young animal. The cruciate ligaments and menisci were identified on CT, with MRI providing better visualization. The mean values of CT measurements (cm²) in the sagittal section included patella (2.475), medial fabella (0.481), lateral fabella (0.772), popliteal sesamoid (0.222), and medial meniscus (0.051). No differences were found in HU values between the central trabecular bone of the patella and popliteal sesamoid, the cortical bone of the patella and lateral and medial fabellas, or the cortical bone of the patella and popliteal sesamoid. In conclusion, the descriptions of the stifle of Puma concolor from the different imaging methods contribute to understanding the species and can serve as a basis for identifying alterations. Full article

The generalization of Physics-Informed Neural Networks (PINNs) used to solve the inhomogeneous Helmholtz equation in a simplified three-dimensional room is investigated. PINNs are appealing since they can efficiently integrate a partial differential equation and experimental data by minimizing a loss function. However, a previous study experienced limitations in acoustics regarding the source term. A challenging but realistic excitation case is a confined (e.g., single-point) excitation area, yielding a smooth spatial wave field periodically with the wavelength. Compared to studies using smooth (unrealistic) sound excitation, the network’s generalization capabilities regarding a realistic sound excitation are addressed. Different methods like hyperparameter optimization, adaptive refinement, Fourier feature engineering, and locally adaptive activation functions with slope recovery are tested to tailor the PINN’s accuracy to an experimentally validated finite element analysis reference solution computed with openCFS. The hyperparameter study and optimization are conducted regarding the network depth and width, the learning rate, the used activation functions, and the deep learning backends (PyTorch 2.5.1, TensorFlow 2.18.0 1, TensorFlow 2.18.0 2, JAX 0.4.39). A modified (feature-engineered) PINN architecture was designed using input feature engineering to include the dispersion relation of the wave in the neural network. For smoothly (unrealistic) distributed sources, it was shown that the standard PINNs and the feature-engineered PINN converge to the analytic solution, with a relative error of 0.28% and $2\times {10}^{-4}$%, respectively. The locally adaptive activation functions with the slope lead to a relative error of 0.086% with a source sharpness of $s=1$ m. Similar relative errors were obtained for the case $s=0.2$ m using adaptive refinement. The feature-engineered PINN significantly outperformed the results of previous studies regarding accuracy. Furthermore, the trainable parameters were reduced to a fraction by Bayesian hyperparameter optimization (around 5%), and likewise, the training time (around 3%) was reduced compared to the standard PINN formulation. By narrowing this excitation towards a single point, the convergence rate and minimum errors obtained of all presented network architectures increased. The feature-engineered architecture yielded a one order of magnitude lower accuracy of 0.20% compared to 0.019% of the standard PINN formulation with a source sharpness of $s=1$ m. It outperformed the finite element analysis and the standard PINN in terms time needed to obtain the solution, needing 15 min and 30 s on an AMD Ryzen 7 Pro 8840HS CPU (AMD, Santa Clara, CA, USA) for the FEM, compared to about 20 min (standard PINN) and just under a minute of the feature-engineered PINN, both trained on a Tesla T4 GPU (NVIDIA, Santa Clara, CA, USA). Full article

The multi-sublattice ferrimagnet Co₂FeO₂BO₃, a prominent example of lanthanide-free magnets, was the subject of element-selective studies using X-ray magnetic circular dichroism (XMCD) observations at the L- and K- X-ray absorption edges. Research findings indicate that the distinct magnetic characteristics of Co₂FeO₂BO₃, namely its remarkable high coercivity (which surpasses 7 Tesla at low temperatures), originate from an atypical arrangement of magnetic ions in the crystal structure (sp.gr. Pbam). The antiferromagnetic nature of the Co²⁺-O-Fe³⁺ exchange interaction was confirmed by identifying the spin and orbital contributions to the total magnetization from Co (m_L = 0.27 ± 0.1 μ_B/ion and m^eff_S = 0.53 ± 0.1 μ_B/ion) and Fe (m_L = 0.05 ± 0.1 μ_B/ion and m^eff_S = 0.80 ± 0.1 μ_B/ion) ions through element-selective XMCD analysis. Additionally, the research explicitly revealed that the strong magnetic anisotropy is a result of the significant unquenched orbital magnetic moment of Co, a feature that is also present in the related compound Co₃O₂BO₃. A complex magnetic structure in Co₂FeO₂BO₃, with infinite Co²⁺O₆ layers in the bc-plane and strong antiferromagnetic coupling through Fe³⁺ ions, is suggested by element-selective hysteresis data, which revealed that Co²⁺ ions contribute both antiferromagnetic and ferromagnetic components to the total magnetization. The findings underline the suitability of Co₂FeO₂BO₃ for applications in extreme environments, such as low temperatures and high magnetic fields, where its unique magnetic topology and anisotropy can be harnessed for advanced technologies, including materials for space exploration and quantum devices. This XMCD study opens the door to the production of novel high-coercivity, lanthanide-free magnetic materials by showing that targeted substitution at specific crystallographic sites can significantly enhance the magnetic properties of such materials. Full article

The implementation of clinical 7T MRI presents both opportunities and challenges for advanced medical imaging. This tutorial provides practical considerations and experiences with 7T MRI in clinical settings. We first explore the history and evolution of MRI technology, highlighting the benefits of increased signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and susceptibility at 7T. Technical challenges such as increased susceptibility artifacts and RF inhomogeneity are also discussed, along with innovative adaptations. This review also discusses hardware and software considerations, including new parallel transmission head coils and advanced image processing techniques to optimize image quality. Safety considerations, such as managing tissue heating and susceptibility to artifacts, are also discussed. Additionally, clinical applications of 7T MRI are examined, focusing on neurological conditions such as epilepsy, multiple sclerosis, and vascular imaging. Emerging trends in the use of 7T MRI for spectroscopy, perfusion imaging, and multinuclear imaging are explored, with insights into the future of ultra-high-field MRI in clinical practice. This review aims to provide clinicians, technologists, and researchers with a roadmap for successfully implementing 7T MRI in both research and clinical environments. Full article

Diffusion magnetic resonance imaging (dMRI) allows for a non-invasive visualization and quantitative assessment of white matter architecture in the brain by characterizing restrictions on the random motion of water molecules. Ultra-high field MRI scanners, such as those operating at 7 Tesla (7T) or higher, can boost the signal-to-noise ratio (SNR) to improve dMRI compared with what is attainable at conventional field strengths such as 3T or 1.5T. However, wavelength effects at 7T cause reduced transmit magnetic field efficiency in the human brain, mainly in the posterior fossa, manifesting as signal dropouts in this region. Recently, we reported a simple approach of using a wireless radiofrequency (RF) surface array to improve transmit efficiency and signal sensitivity at 7T. In this study, we demonstrate the feasibility and effectiveness of the RF enhancer in improving in vivo dMRI at 7T. The electromagnetic simulation results demonstrated a 2.1-fold increase in transmit efficiency with the use of the RF enhancer. The experimental results similarly showed a 1.9-fold improvement in transmit efficiency and a 1.4-fold increase in normalized SNR. These improvements effectively mitigated signal dropouts in regions with inherently lower SNR, such as the cerebellum, resulting in a better depiction of principal fiber orientations and an enhanced visualization of extended tracts. Full article

This paper investigated the correlation between magnetic resonance spectroscopic imaging (MRSI) and magnetic resonance fingerprinting (MRF) in glioma patients by comparing neuro-oncological markers obtained from MRSI to T1/T2 maps from MRF. Data from 12 consenting patients with gliomas were analyzed by defining hotspots for T1, T2, and various metabolic ratios, and comparing them using Sørensen–Dice similarity coefficients (DSCs) and the distances between their centers of intensity (COIDs). The median DSCs between MRF and the tumor segmentation were 0.73 (T1) and 0.79 (T2). The DSCs between MRSI and MRF were the highest for Gln/tNAA (T1: 0.75, T2: 0.80, tumor: 0.78), followed by Gly/tNAA (T1: 0.57, T2: 0.62, tumor: 0.54) and tCho/tNAA (T1: 0.61, T2: 0.58, tumor: 0.45). The median values in the tumor hotspot were T1 = 1724 ms, T2 = 86 ms, Gln/tNAA = 0.61, Gly/tNAA = 0.28, Ins/tNAA = 1.15, and tCho/tNAA = 0.48, and, in the peritumoral region, were T1 = 1756 ms, T2 = 102 ms, Gln/tNAA = 0.38, Gly/tNAA = 0.20, Ins/tNAA = 1.06, and tCho/tNAA = 0.38, and, in the NAWM, were T1 = 950 ms, T2 = 43 ms, Gln/tNAA = 0.16, Gly/tNAA = 0.07, Ins/tNAA = 0.54, and tCho/tNAA = 0.20. The results of this study constitute the first comparison of 7T MRSI and 3T MRF, showing a good correspondence between these methods. Full article

Perfusion measures of the total vasculature are commonly derived with gradient-echo (GE) dynamic susceptibility contrast (DSC) MR images, which are acquired during the early passes of a contrast agent. Alternatively, spin-echo (SE) DSC can be used to achieve specific sensitivity to the capillary signal. For an improved contrast-to-noise ratio, ultra-high-field MRI makes this technique more appealing to study cerebral microvascular physiology. Therefore, this study assessed the applicability of SE-DSC MRI at 7 T. Forty-one elderly adults underwent 7 T MRI using a multi-slice SE-EPI DSC sequence. The cerebral blood volume (CBV) and cerebral blood flow (CBF) were determined in the cortical grey matter (CGM) and white matter (WM) and compared to values from the literature. The relation of CBV and CBF with age and sex was investigated. Higher CBV and CBF values were found in CGM compared to WM, whereby the CGM-to-WM ratios depended on the amount of largest vessels excluded from the analysis. CBF was negatively associated with age in the CGM, while no significant association was found with CBV. Both CBV and CBF were higher in women compared to men in both CGM and WM. The current study verifies the possibility of quantifying cerebral microvascular perfusion with SE-DSC MRI at 7 T. Full article