Whole-tumor histogram analysis of synthetic magnetic resonance imaging predicts isocitrate dehydrogenase mutation status in gliomas.

Background: An accurate assessment of isocitrate dehydrogenase (IDH) status in patients with glioma is crucial for treatment planning and is a key factor in predicting patient outcomes. In this study, we investigated the potential value of whole-tumor histogram metrics derived from synthetic magnetic resonance imaging (MRI) in distinguishing IDH mutation status between astrocytoma and glioblastoma. Methods: In this prospective study, 80 glioma patients were enrolled from September 2019 to June 2022. All patients underwent pre- and post-contrast synthetic MRI scan protocol. Immunohistochemistry (IHC) staining or gene sequencing were used to assess IDH mutation status in tumor tissue samples. Whole-tumor histogram metrics, including T1, T2, proton density (PD), etc., were extracted from the quantitative maps, while radiological features were assessed by synthetic contrast-weighted maps. Basic clinical features of the patients were also evaluated. Differences in clinical, radiological, and histogram metrics between IDH-mutant astrocytoma and IDH-wildtype glioblastoma were analyzed using univariate analyses. Variables with statistical significance in univariate analysis were included in multivariate logistic regression analysis to develop the combined model. Receiver operating characteristic (ROC) and area under the curve (AUC) were used to assess the diagnostic performance of metrics and models. Results: The histopathologic analysis revealed that of the 80 cases, 41 were classified as IDH-mutant astrocytoma and 39 as IDH-wildtype glioblastoma. Compared to IDH-wildtype glioblastoma, IDH-mutant astrocytoma showed significantly lower T1 [10th percentile (10th), mean, and median] and post-contrast PD (10th, 90th percentile, mean, median, and maximum) values as well as higher post-contrast T1 (cT1) (10th, mean, median, and minimum) values (all P<0.05). The combined model (T1-10th + cT1-10th + age) was developed by integrating the independent influencing factors of IDH-mutant astrocytoma using the multivariate logistic regression. The diagnostic performance of this model [AUC =0.872 (0.778-0.936), sensitivity =75.61%, and specificity =89.74%] was superior to the clinicoradiological model, which was constructed using age and enhancement degree (AUC =0.822 (0.870-0.898), P=0.035). Conclusions: The combined model constructed using histogram metrics derived from synthetic MRI could be a valuable preoperative tool to distinguish IDH mutation status between astrocytoma and glioblastoma, and subsequently, could assist in the decision-making process of pretreatment.

Macroscopic assembly of 2D materials for energy storage and seawater desalination.

Since the discovery of graphene in 2004, two-dimensional (2D) materials have attracted widespread attention due to their excellent physical and chemical properties in the fields of energy, environment, catalysis, and optoelectronics. However, there are still many key problems in the process of practical application. To further promote the potential of 2D materials for practical applications, macroscopic assembly of 2D materials is crucial for the continued development of 2D materials, especially in the fields of energy storage and seawater desalination. Therefore, this review focuses on the latest progress and current status related to the macroscopic assembly of 2D materials, including 1D fibers, 2D films, and 3D architectures. In addition, the application of macroscopic bodies assembled based on 2D materials in the fields of energy storage and seawater desalination is also introduced. Finally, future directions for the macroscopic assembly of 2D materials and their applications are prospected.

Photoelectrocatalytic Processes of TiO2 Film: The Dominating Factors for the Degradation of Methyl Orange and the Understanding of Mechanism.

Various thicknesses of TiO2 films were prepared by the sol-gel method and spin-coating process. These prepared TiO2 films exhibit thickness-dependent photoelectrochemical performance. The 1.09-µm-thickTiO2 film with 20 spin-coating layers (TiO2-20) exhibits the highest short circuit current of 0.21 mAcm-2 and open circuit voltage of 0.58 V among all samples and exhibits a low PEC reaction energy barrier and fast kinetic process. Photoelectrocatalytic (PEC) degradation of methyl orange (MO) by TiO2 films was carried out under UV light. The roles of bias, film thickness, pH value, and ion properties were systematically studied because they are the four most important factors dominating the PEC performance of TiO2 films. The optimized values of bias, film thickness, and pH are 1.0 V, 1.09 µm, and 12, respectively, which were obtained according to the data of the PEC degradation of MO. The effect of ion properties on the PEC efficiency of TiO2-20 was also analyzed by using halide as targeted ions. The "activated" halide ions significantly promoted the PEC efficiency and the order was determined as Br > Cl > F. The PEC efficiency increased with increasing Cl content, up until the optimized value of 30 × 10-3 M. Finally, a complete degradation of MO by TiO2-20 was achieved in 1.5 h, with total optimization of the four factors: 1.0 V bias, 1.09-µm-thick, pH 12, and 30 × 10-3 M Cl ion content. The roles of reactive oxygen species and electric charge of photoelectrodes were also explored based on photoelectrochemical characterizations and membrane-separated reactors. Hydrogen peroxide, superoxide radical, and hydroxyl radical were found responsible for the decolorization of MO.

White matter regeneration induced by aligned fibrin nanofiber hydrogel contributes to motor functional recovery in canine T12 spinal cord injury.

A hierarchically aligned fibrin hydrogel (AFG) that possesses soft stiffness and aligned nanofiber structure has been successfully proven to facilitate neuroregeneration in vitro and in vivo. However, its potential in promoting nerve regeneration in large animal models that is critical for clinical translation has not been sufficiently specified. Here, the effects of AFG on directing neuroregeneration in canine hemisected T12 spinal cord injuries were explored. Histologically obvious white matter regeneration consisting of a large area of consecutive, compact and aligned nerve fibers is induced by AFG, leading to a significant motor functional restoration. The canines with AFG implantation start to stand well with their defective legs from 3 to 4 weeks postoperatively and even effortlessly climb the steps from 7 to 8 weeks. Moreover, high-resolution multi-shot diffusion tensor imaging illustrates the spatiotemporal dynamics of nerve regeneration rapidly crossing the lesion within 4 weeks in the AFG group. Our findings indicate that AFG could be a potential therapeutic vehicle for spinal cord injury by inducing rapid white matter regeneration and restoring locomotion, pointing out its promising prospect in clinic practice.

Effects of Levodopa Therapy on Cerebral Arteries and Perfusion in Parkinson's Disease Patients.

BACKGROUND: Levodopa is the most-commonly used therapy for Parkinson's Disease (PD). Imaging findings show increased cerebral blood flow (CBF) response to levodopa, but the artery morphological change is less studied. PURPOSE: To investigate the effect of levodopa on cerebral arteries and CBF. STUDY TYPE: Prospective. POPULATION: 57 PD patients (56 ± 10 years, 26 males) and 17 age-matched healthy controls (AMC, 57 ± 9 years, 9 males) were scanned at baseline (OFF). Patients were rescanned 50 minutes after taking levodopa (ON). FIELD STRENGTH AND SEQUENCE: 3 T; Simultaneous noncontrast angiography intraplaque imaging (SNAP) based on turbo field echo; Pseudo-continuous arterial spin labeling (PCASL) based on echo-planner imaging. ASSESSMENT: The Unified Parkinson's Disease Rating Scale (UPDRS-III) was used to assess the disease severity. Length and radius of arteries were measured from SNAP images. CBF was calculated from PCASL images globally and regionally. STATISTICAL TESTS: Mann Whitney U tests were conducted in comparing PD vs. AMC. Wilcoxon matched-pairs signed rank tests were used in comparing OFF vs. ON, and the more-affected vs. the less-affected hemisphere in PD. Linear regressions were performed to test the correlations of neuroimaging findings with behavioral changes. Significance threshold was P < 0.05 with Bonferroni correction. RESULTS: PD patients were identified with significantly lower CBF (PD OFF Mean = 40.15 ± 5.99, AMC Mean = 43.48 ± 6.21 mL/100 g/min) and shortened total artery length (PD OFF Mean = 5851.07 ± 1393.45, AMC Mean = 7479.16 ± 1335.93 mm). Levodopa elevated CBF of PD brains (PD ON Mean = 41.48 ± 6.32 mL/100 g/min) and expanded radius of proximal arteries. Artery radius change significantly correlated with CBF change in corresponding territories (r = 0.559 for Internal Carotid Arteries, r = 0.448 for Basilar Artery, and r = 0.464 for Middle Cerebral Artery M1). Global CBF significantly related to UPDRS-III (r = -0.391) post-levodopa. DATA CONCLUSION: Levodopa can increase CBF by dilating proximal arteries. LEVEL OF EVIDENCE: 1 TECHNICAL EFFICACY STAGE: 4.

Improving distortion correction for isotropic high-resolution 3D diffusion MRI by optimizing Jacobian modulation.

PURPOSE: To improve distortion correction for isotropic high-resolution whole-brain 3D diffusion MRI when in a time-saving acquisition scenario. THEORY AND METHODS: Data were acquired using simultaneous multi-slab (SMSlab) acquisitions, with a b = 0 image pair encoded by reversed polarity gradients (RPG) for phase encoding (PE) and diffusion weighted images encoded by a single PE direction. Eddy current-induced distortions were corrected first. During the following susceptibility distortion correction, image deformation was first corrected by the field map estimated from the b = 0 image pair. Intensity variation was subsequently corrected by Jacobian modulation. Two Jacobian modulation methods were compared. They calculated the Jacobian modulation map from the field map, or from the deformation corrected b = 0 image pair, termed as JField and JRPG , respectively. A modified version of the JRPG method, with proper smoothing, was further proposed for improved correction performance, termed as JRPG-smooth . RESULTS: Compared to JField modulation, less remaining distortions are observed when using the JRPG and JRPG-smooth methods, especially in areas with large B0 field inhomogeneity. The original JRPG method causes signal-to-noise ratio (SNR) deficiency problem, which manifests as degraded SNR of the diffusion weighted images, while the JRPG-smooth method maintains the original image SNR. Less estimation errors of diffusion metrics are observed when using the JRPG-smooth method. CONCLUSION: This study improves the distortion correction for isotropic high-resolution whole-brain 3D diffusion MRI by optimizing Jacobian modulation. The optimized method outperforms the conventional JField method regarding intensity variation correction and accuracy of diffusion metrics estimation, and outperforms the original JRPG method regarding SNR performance.

Directional axonal regrowth induced by an aligned fibrin nanofiber hydrogel contributes to improved motor function recovery in canine L2 spinal cord injury.

Spinal cord injuries (SCI) normally disrupt the long axonal tracts of the spinal cord and cause permanent neurological deficits, for which there is currently a lack of effective therapeutic methods. Biomaterial-based regenerative medicine is a pivotal strategy to induce axonal regeneration through delivery of biophysical and/or biochemical regulatory cues by biomaterials. We previously fabricated a hierarchically aligned fibrin hydrogel (AFG) that could promote neurogenic differentiation of stem cells in vitro and has been successfully applied for peripheral nerve and spinal cord regeneration in rats. In this study, AFG was used to repair a canine lumbar segment 2 hemisection spinal cord injury, and the consistency of histological, imageological and behavioral results was compared. AFG was used to construct an aligned fiber bridge that supported cell adhesion in vitro and rapidly facilitated tissue invasion along the long axis of fibers in vivo, Moreover, in vivo results demonstrated regrowth of axons in an oriented pattern connecting the rostral and caudal stumps. Consistent results were confirmed by diffusion tensor imaging, which allowed successful tracing of reconnected nerve fibers across the defect. As a result, directional axonal regrowth contributed to significantly improved recovery of motor functional behavior of SCI canines with AFG implantation. Our results suggest that AFG has great promise for rapidly directing axonal regrowth for nerve regeneration.

Angiographic contrast mechanism comparison between Simultaneous Non-contrast Angiography and intraPlaque hemorrhage (SNAP) sequence and Time of Flight (TOF) sequence for intracranial artery.

PURPOSE: To theoretically compare the MR angiography (MRA) contrast mechanism of Time of Flight (TOF) and Simultaneous Non-contrast Angiography and intraPlaque hemorrhage (SNAP) for intracranial artery imaging with in-vivo validation. METHODS: The contrast ratio (CR) of SNAP and TOF was simulated under different blood velocities and travel distance that the blood had flown through. The CR and the slope of CR with respect to blood velocity of SNAP and TOF were compared in theoretical simulation. Two healthy subjects (a 60 years old female and a 29 years old male) were imaged on a 3 T MR scanner with SNAP, TOF and phase contrast (PC) images as the validation set. The measured CR from the images in validation set was compared with the theoretically simulated CR by Person's correlation coefficient. The ratio of CR difference to velocity difference in the validation set was compared between TOF and SNAP with Student's t-test. Thirty patients (21 males, age: 48 ±â€¯13.8 years) with carotid artery atherosclerotic plaque were imaged with both TOF and SNAP as the comparison test. Between TOF and SNAP, the CR and total artery length were compared with Student's t-test, and the prevalence of stenosis was compared with Cohen's kappa in comparison test. RESULTS: The theoretically simulated CR was significantly correlated with in-vivo measured CR from the validation set for TOF (p < 0.001) and SNAP (p < 0.001). The simulation revealed that the CR of SNAP was higher than that of TOF when the blood velocity and travel distance were within the range to have effective MRA contrast. Similarly, the in-vivo comparison test showed that SNAP had higher CR (p < 0.001 for all tested intracranial arteries) and longer total artery length (1.4 ±â€¯0.4 m vs 1.2 ±â€¯0.2 m, p < 0.001) than TOF. The stenosis detection performance was similar between TOF and SNAP (Cohen's kappa 0.72; 95% confidence interval: 0.51-0.93). Moreover, compared with TOF, SNAP showed higher slope of CR with respect to velocity in simulation (0.06 ±â€¯0.02 s/cm vs 0.02 ±â€¯0.05 s/cm, p < 0.001), and higher ratio of CR difference to velocity difference in validation test (0.47 ±â€¯0.38 s/cm vs 0.19 ±â€¯0.38 s/cm, p = 0.001). CONCLUSIONS: Compared with TOF, the SNAP shows better performance to visualize distal intracranial artery and worse performance to visualize ICA, and is more sensitive to blood velocity.

Predicting the Post-therapy Severity Level (UPDRS-III) of Patients With Parkinson's Disease After Drug Therapy by Using the Dynamic Connectivity Efficiency of fMRI.

Parkinson's disease (PD) is a multi-systemic disease in the brain arising from the dysfunction of several neural networks. The diagnosis and treatment of PD have gained more attention for clinical researchers. While there have been many fMRI studies about functional topological changes of PD patients, whether the dynamic changes of functional connectivity can predict the drug therapy effect is still unclear. The primary objective of this study was to assess whether large-scale functional efficiency changes of topological network are detectable in PD patients, and to explore whether the severity level (UPDRS-III) after drug treatment can be predicted by the pre-treatment resting-state fMRI (rs-fMRI). Here, we recruited 62 Parkinson's disease patients and calculated the dynamic nodal efficiency networks based on rs-fMRI. With connectome-based predictive models using the least absolute shrinkage and selection operator, we demonstrated that the dynamic nodal efficiency properties predict drug therapy effect well. The contributed regions for the prediction include hippocampus, post-central gyrus, cingulate gyrus, and orbital gyrus. Specifically, the connections between hippocampus and cingulate gyrus, hippocampus and insular gyrus, insular gyrus, and orbital gyrus are positively related to the recovery (post-therapy severity level) after drug therapy. The analysis of these connection features may provide important information for clinical treatment of PD patients.

Distortion correction for high-resolution single-shot EPI DTI using a modified field-mapping method.

PURPOSE: The widely used single-shot EPI (SS-EPI) diffusion tensor imaging (DTI) suffers from strong image distortion due to B0 inhomogeneity, especially for high-resolution imaging. Traditional methods such as the field-mapping method and the top-up method have various deficiencies in high-resolution SS-EPI DTI distortion correction. This study aims to propose a robust distortion correction approach, which combines the advantages of traditional methods and overcomes their deficiencies, for high-resolution SS-EPI DTI. METHODS: The proposed correction method is based on the echo planar spectroscopic imaging field-mapping followed by an intensity correction procedure. To evaluate the efficacy of distortion correction, the proposed method was compared with the conventional field-mapping method and the top-up method, using a newly developed quantitative evaluation framework. The correction results were also compared with multi-shot EPI DTI to investigate whether the proposed method can provide high-resolution SS-EPI DTI with high geometric fidelity and high time efficiency. RESULTS: The results show that accurate field-mapping and intensity correction are critical to distortion correction in high-resolution SS-EPI DTI. The proposed method can provide more precise field maps and better correction results than the other two methods (p < 0.0001), and the corrected images show higher geometric fidelity than those from MS-EPI DTI. CONCLUSION: An effective method is proposed to reduce image distortion in high-resolution SS-EPI DTI. It is practical to achieve high-resolution DTI with high time efficiency and high structure accuracy using this method.

Intracranial simultaneous noncontrast angiography and intraplaque hemorrhage (SNAP) MRA: Analyzation, optimization, and extension for dynamic MRA.

PURPOSE: Simultaneous noncontrast angiography and intraplaque (SNAP) imaging, as a noncontrast-enhanced MRA technique, may not provide consistent vessel visualization for intracranial artery imaging among subjects. This study aims to investigate the underlying mechanism and extend SNAP to dynamic MRA. METHODS: The cause of the instability of intracranial SNAP-MRA was investigated through theoretical analysis and simulations. The scan parameters, including TI and flip angle, were optimized for reliable imaging. In vivo experiments were conducted to validate the simulation results. The simulation results were correlated with real intracranial blood flow by introducing the concept of blood travel time, and intracranial SNAP-MRA was revealed to reflect the cerebral blood expanse region in 5 TI. A new noncontrast-enhanced dynamic MRA technique, termed 4D SNAP-MRA, was proposed and demonstrated through in vivo scans. RESULTS: The cause of the instability of intracranial SNAP-MRA was proved to be the slow or fast blood flow in the imaging slab. This instability can be mitigated by adjusting TI and flip angle in the SNAP sequence. The proposed 4D SNAP-MRA can provide dynamic visualization of the cerebral blood circulation and cerebral hemodynamic information such as blood travel time. CONCLUSION: The 3D SNAP-MRA with optimal imaging parameters can generate cerebral angiography with hemodynamic information, and the 4D SNAP-MRA provides dynamic visualization of the cerebral blood circulation.

The effects of navigator distortion and noise level on interleaved EPI DWI reconstruction: a comparison between image- and k-space-based method.

PURPOSE: To study the effects of 2D navigator distortion and noise level on interleaved EPI (iEPI) DWI reconstruction, using either the image- or k-space-based method. METHODS: The 2D navigator acquisition was adjusted by reducing its echo spacing in the readout direction and undersampling in the phase encoding direction. A POCS-based reconstruction using image-space sampling function (IRIS) algorithm (POCSIRIS) was developed to reduce the impact of navigator distortion. POCSIRIS was then compared with the original IRIS algorithm and a SPIRiT-based k-space algorithm, under different navigator distortion and noise levels. RESULTS: Reducing the navigator distortion can improve the reconstruction of iEPI DWI. The proposed POCSIRIS and SPIRiT-based algorithms are more tolerable to different navigator distortion levels, compared to the original IRIS algorithm. SPIRiT may be hindered by low SNR of the navigator. CONCLUSION: Multi-shot iEPI DWI reconstruction can be improved by reducing the 2D navigator distortion. Different reconstruction methods show variable sensitivity to navigator distortion or noise levels. Furthermore, the findings can be valuable in applications such as simultaneous multi-slice accelerated iEPI DWI and multi-slab diffusion imaging.

Segmentation of gray matter, white matter, and CSF with fluid and white matter suppression using MP2RAGE.

BACKGROUND: MP2RAGE can generate uniform T1 -weighted images, which have been used for brain segmentation. However, there remain concerns about carrying out fast brain segmentation. PURPOSE: To propose an acquisition-based method for fast segmentation of gray matter (GM), white matter (WM), and cerebrospinal fluid (CSF) of healthy human brains with fluid and white matter suppression (FLAWS) using MP2RAGE. STUDY TYPE: Prospective. SUBJECTS: 12 volunteers (23-28 years, seven subjects; 51-62 years, five subjects). FIELD STRENGTH/SEQUENCES: 3T/3D MPRAGE and FLAWS. ASSESSMENT: The proposed method was evaluated by calculating tissue volumes and the spatial overlap with the segmentation results from FSL and SPM12. The processing time was recorded. STATISTICAL TESTS: A paired t-test was used to compare the tissue volumes of the proposed method with those from other segmentation methods RESULTS: For the 12 subjects, the tissue volume difference between the proposed and SPM12 were 3.2 ± 2.8%, 4.2 ± 2.5%, 18.2 ± 13.1% for GM, WM, and CSF, respectively. The relative difference between the proposed and FSL was over 14% for all tissue classes. The spatial overlap between the proposed and other methods were 87-94% for GM and WM and less than 80% for CSF. The GM and WM volumes of the proposed method were not significantly different from those of SPM12 using MPRAGE as the input (P = 0.5540 and P = 0.3115, respectively). The rest of the comparisons all showed significant differences between the proposed and other methods. Statistical analysis of the two subgroups yielded similar results. The mean processing time of one subject was 6.5, 185, and 165 seconds for the proposed method, FSL, and SPM12, respectively. DATA CONCLUSION: Our method may be accurate for the segmentation of most brain structures using FLAWS. In addition, the proposed method is fast and applicable to the two distinct age ranges. LEVEL OF EVIDENCE: 2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2018;48:1540-1550.