During the last decades,advances in the understanding of genetic,cellular,and microstructural alterations associated to Huntington's disease(HD)have improved the understanding of this progressive and fatal illness...During the last decades,advances in the understanding of genetic,cellular,and microstructural alterations associated to Huntington's disease(HD)have improved the understanding of this progressive and fatal illness.However,events related to early neuropathological events,neuroinflammation,deterioration of neuronal connectivity and compensatory mechanisms still remain vastly unknown.Ultra-high field diffusion MRI(UHFD-MRI)techniques can contribute to a more comprehensive analysis of the early microstructural changes observed in HD.In addition,it is possible to evaluate if early imaging microstructural parameters might be linked to histological biomarkers.Moreover,qualitative studies analyzing histological complexity in brain areas susceptible to neurodegeneration could provide information on inflammatory events,compensatory increase of neuroconnectivity and mechanisms of brain repair and regeneration.The application of ultra-high field diffusion-MRI technology in animal models,particularly the R6/1 mice(a common preclinical mammalian model of HD),provide the opportunity to analyze alterations in a physiologically intact model of the disease.Although some disparities in volumetric changes across different brain structures between preclinical and clinical models has been documented,further application of different diffusion MRI techniques used in combination like diffusion tensor imaging,and neurite orientation dispersion and density imaging have proved effective in characterizing early parameters associated to alteration in water diffusion exchange within intracellular and extracellular compartments in brain white and grey matter.Thus,the combination of diffusion MRI imaging techniques and more complex neuropathological analysis could accelerate the discovery of new imaging biomarkers and the early diagnosis and neuromonitoring of patients affected with HD.展开更多
Diffusion MRI is an important technology for detecting human brain nerve pathways,aiding in neuroscience and clinical diagnosis.However,the Multi-ShellMulti-TissueConstrainedSphericalDeconvolution(M-CSD)method,which i...Diffusion MRI is an important technology for detecting human brain nerve pathways,aiding in neuroscience and clinical diagnosis.However,the Multi-ShellMulti-TissueConstrainedSphericalDeconvolution(M-CSD)method,which is a significant technique for reconstructing thefibre orientation distribution func-tion(fODF),requires multishell data with a considerable number of gradient direc-tions to achieve high accuracy.As multishell data are not easy to acquire,the Single-Shell Single-Tissue CSD(S-CSD)suffers from the Partial Volume Effect(PVE).It would be more convenient if we could use single-shell data to reconstruct better fODFs.We propose a novel method that utilizes the spatial structure and anisotropy of dMRI data through a spherical convolution network.We reduce the need for high-quality data by utilizing b=1000 s/mm2 with 60 gradient directions or even less.Our results show that our method outperforms the traditional S-CSD when compared to the M-CSD results as our gold standard.展开更多
Objective To evaluate the value of MRI diffusion weighted imaging in localization of prostate cancer with whole-mount step section pathology. Methods We treated 36 patients using laparoscopic radical prostatectomy fro...Objective To evaluate the value of MRI diffusion weighted imaging in localization of prostate cancer with whole-mount step section pathology. Methods We treated 36 patients using laparoscopic radical prostatectomy from Oct. 2009 to Jun. 2010. Patients who did not have an MRL /DWI examination or a surgical history of pros-展开更多
Nuclear magnetic resonance(NMR)measurements of water diffusion have been extensively used to probe microstructure in porous materials,such as biological tissue,however primarily using pulsed gradient spin echo(PGSE)me...Nuclear magnetic resonance(NMR)measurements of water diffusion have been extensively used to probe microstructure in porous materials,such as biological tissue,however primarily using pulsed gradient spin echo(PGSE)methods.Low-field single-sided NMR systems have built-in static gradients(SG)much stronger than typical PGSE maximum gradient strengths,which allows for the signal attenuation at extremely high b-values to be explored.Here,we perform SG spin echo(SGSE)and SG stimulated echo(SGSTE)diffusion measurements on biological cells,tissues,and gels.Measurements on fixed and live neonatal mouse spinal cord,lobster ventral nerve cord,and starved yeast cells all show multiexponential signal attenuation on a scale of b with significant signal fractions observed at b×Do>1 with b as high as 400 ms/um2.These persistent signal fractions trend with surface-to-volume ratios for these systems,as expected from porous media theory.An exception found for the case of fixed vs.live spinal cords was attributed to faster exchange or permeability in live spinal cords than in fixed spinal cords on the millisecond timescale.Data suggests the existence of multiple exchange processes in neural tissue,which may be relevant to the modeling of time-dependent diffusion in gray matter.The observed multi-exponential attenuation is from protons on water and not macromolecules because it remains proportional to the normalized signal when a specimen is washed with D20.The signal that persists to b×Do>1 is also drastically reduced after delipidation,indicating that it originates from lipid membranes that restrict water diffusion.The multiexponential or stretched exponential character of the signal attenuation at b×Do>1 appears mono-exponential when viewed on a scale of(b×Do)/3,suggesting it may originate from localization or motional averaging of water near membranes on sub-micron length scales.To try to disambiguate these two contributions,signal attenuation curves were compared at varying temperatures.While the curves align when normalizing them using the localization length scale,they separate on a motional averaging length scale.This supports localization as the source of non-Gaussian displacements,but this interpretation is still provisional due to the possible confounds of heterogeneity,exchange,and relaxation.Measurements on two types of gel phantoms designed to mimic extracellular matrix.one with charged functional groups synthesized from polyacrylic acid(PAC)and another with uncharged functional groups synthesized from polyacrylamide(PAM),both exhibit signal at b×Do>1,potentially due to water interacting with macromolecules.These preliminary finding motivate future research into contrast and attenuation mechanisms in tissue with low-field,high-gradient NMR。展开更多
Background:Ultra high field diffusion magnetic resonance imaging(dMRI)provides diffusion-weighted(DW)images with a high signal-to-noise ratio,but increases inhomogeneity,which affects the accuracy of dMRI metric recon...Background:Ultra high field diffusion magnetic resonance imaging(dMRI)provides diffusion-weighted(DW)images with a high signal-to-noise ratio,but increases inhomogeneity,which affects the accuracy of dMRI metric recon-struction.Current methods for correcting inhomogeneity rarely consider the accuracy of the reconstructed dMRI metrics.Deep learning models for reconstructing metrics from dMRI signals typically assume that DW images have a homogeneous intensity.To address these challenges,we propose a deep learning model capable of directly reconstructing high-accuracy dMRI metric maps from inhomogeneous DW images.Methods:An attention-based q-space inhomogeneity-resistant reconstruction network(qIRR-Net)is proposed for the voxel-wise reconstruction of diffusion tensor imaging and diffusion kurtosis imaging metrics.A training procedure based on data augmentation and consistency loss is introduced to ensure that the reconstruction results of qIRR-Net are not affected by signal in-homogeneity.The 3T and 7T dMRI data from the Human Connectome Project are used for model training,testing,and evaluation.Results:On the 3T dMRI data with simulated inhomogeneity,qIRR-Net improves the peak signal-to-noise ratio by 5.39 and the structural similarity index measure by 0.18 compared with weighted linear least-squares fitting.On the 7T dMRI data,the metric maps reconstructed by qIRR-Net not only exhibit clearer tissue structures but also demonstrate greater stability compared with the weighted linear least-squares results.Conclusions:The proposed qIRR-Net enables the accurate reconstruction of dMRI metrics from inhomogeneous DW images.This approach could poten-tially be expanded to obtain multiple artifact-free metric maps from ultrahigh field dMRI for neuroscience research and neurology applications.展开更多
To evaluate the effect of the positive-indefinite matrix on the diffusion tensor-derived parameters, a modified algorithm is proposed for calculating these parameters. Magnetic resonance （MR） diffusion tensor images...To evaluate the effect of the positive-indefinite matrix on the diffusion tensor-derived parameters, a modified algorithm is proposed for calculating these parameters. Magnetic resonance （MR） diffusion tensor images of five healthy volunteers are collected. The diffusion sensitive gradient magnetic fields are applied along 25 directions and the diffusion weighting value is 1 000 s/mm^2. Many positive-indefinite diffusion tensors can be found in the white matter area, such as the genu and the splenium of corpus callosum. Due to the positive-indefinite matrix, the mean diffusivity （MD） and the fractional anisotropy （FA） are under-estimated and over-estimated by using the conventional algorithm. Thus, the conventional algorithm is modified by using the absolute values of all eigenvalues. Results show that both the robustness and the reliability for deriving these parameters are improved by the modified algorithm.展开更多
Water exchange between the different compartments of a heterogeneous specimen can be characterized via diffusion magnetic resonance imaging(dMRI).Many analysis frameworks using dMRI data have been proposed to describe...Water exchange between the different compartments of a heterogeneous specimen can be characterized via diffusion magnetic resonance imaging(dMRI).Many analysis frameworks using dMRI data have been proposed to describe exchange,often using a double diffusion encoding(DDE)stimulated echo sequence.Techniques such as diffusion exchange weighted imaging(DEWI)and the filter exchange and rapid exchange models,use a specific subset of the full space DDE signal.In this work,a general representation of the DDE signal was employed with different sampling schemes(namely constant b1,diagonal and anti-diagonal)from the data reduction models to estimate exchange.A near-uniform sampling scheme was proposed and compared with the other sampling schemes.The filter exchange and rapid exchange models were also applied to estimate exchange with their own subsampling schemes.These subsampling schemes and models were compared on both simulated data and experimental data acquired with a benchtop MR scanner.In synthetic data,the diagonal and near-uniform sampling schemes performed the best due to the consistency of their estimates with the ground truth.In experimental data,the shifted diagonal and near-uniform sampling schemes outperformed the others,yielding the most consistent estimates with the full space estimation.The results suggest the feasibility of measuring exchange using a general representation of the DDE signal along with variable sampling schemes.In future studies,algorithms could be further developed for the optimization of sampling schemes,as well as incorporating additional properties,such as geometry and diffusion anisotropy,into exchange frameworks.展开更多
Searching for effective biomarkers is one of the most challenging tasks in the research ？eld of Autism Spectrum Disorder（ASD）. Magnetic resonance imaging（MRI） provides a non-invasive and powerful tool for investi...Searching for effective biomarkers is one of the most challenging tasks in the research ？eld of Autism Spectrum Disorder（ASD）. Magnetic resonance imaging（MRI） provides a non-invasive and powerful tool for investigating changes in the structure, function, maturation,connectivity, and metabolism of the brain of children with ASD. Here, we review the more recent MRI studies in young children with ASD, aiming to provide candidate biomarkers for the diagnosis of childhood ASD. The review covers structural imaging methods, diffusion tensor imaging, resting-state functional MRI, and magnetic resonance spectroscopy. Future advances in neuroimaging techniques, as well as cross-disciplinary studies and largescale collaborations will be needed for an integrated approach linking neuroimaging, genetics, and phenotypic data to allow the discovery of new, effective biomarkers.展开更多
Traumatic brain injury is a major cause of death and disability. This is a brief report based on a symposium presentation to the 2014 Chinese Neurotrauma Association Meeting in San Francisco, USA. It covers the work f...Traumatic brain injury is a major cause of death and disability. This is a brief report based on a symposium presentation to the 2014 Chinese Neurotrauma Association Meeting in San Francisco, USA. It covers the work from our laboratory in applying multimodal MRI to study experimental traumatic brain injury in rats with comparisons made to behavioral tests and histology. MRI protocols include structural, perfusion, manganese-enhanced, diffusion-tensor MRI, and MRI of blood-brain barrier integrity and cerebrovascular reactivity.展开更多
Q-space trajectory imaging(QTI)allows non-invasive estimation of microstructural features of heterogeneous porous media via diffusion magnetic resonance imaging performed with generalised gradient waveforms.A recently...Q-space trajectory imaging(QTI)allows non-invasive estimation of microstructural features of heterogeneous porous media via diffusion magnetic resonance imaging performed with generalised gradient waveforms.A recently proposed constrained estimation framework,called QTI+,improved QTI's resilience to noise and data sparsity,thus increasing the reliability of the method by enforcing relevant positivity constraints.In this work we consider expanding the set of constraints to be applied during the fitting of the QTI model.We show that the additional conditions,which introduce an upper bound on the diffusivity values,further improve the retrieved parameters on a publicly available human brain dataset as well as on data acquired from healthy volunteers using a scanner-ready protocol.展开更多
White matter(WM)comprises approximately half of the human brain volume and is primarily composed of bundles of axons and glia.The axons conduct nerve impulses between gray matter(GM)to support information transmission...White matter(WM)comprises approximately half of the human brain volume and is primarily composed of bundles of axons and glia.The axons conduct nerve impulses between gray matter(GM)to support information transmission and coordination within brain networks or circuits.Despite the overwhelming emphasis of human brain imaging on GM,few would deny the importance of the functional contributions of WM to human cognition and behavior.For in vivo brain studies,diffusion magnetic resonance imaging(MRI)has been widely used to delineate WM fibers and measure their microstructural properties,but diffusion MRI reveals little about functional activity.For a long time,we have lacked an in vivo way to quantify functional metrics of wM.In contrast to the widespread application of functional MRI(fMRI)based on blood oxygenation-level-dependent(BOLD)signals to assess GM functions[1],BOLD effects in WM have been regarded as noise or nuisance variables in most neuroimaging studies.展开更多
In this study, we established a Wistar rat model of right middle cerebral artery occlusion and observed pathological imaging changes （T2-weighted imaging [T2WI], T2FLAIR, and diffusion-weighted imaging [DWI]） follow...In this study, we established a Wistar rat model of right middle cerebral artery occlusion and observed pathological imaging changes （T2-weighted imaging [T2WI], T2FLAIR, and diffusion-weighted imaging [DWI]） following cerebral infarction. The pathological changes were divided into three phases： early cerebral infarction, middle cerebral infarction, and late cerebral infarction. In the early cerebral infarction phase （less than 2 hours post-infarction）, there was evidence of intracellular edema, which improved after reperfusion. This improvement was defined as the ischemic penumbra. In this phase, a high DWI signal and a low apparent diffusion coefficient were observed in the right basal ganglia region. By contrast, there were no abnormal T2WI and T2FLAIR signals. For the middle cerebral infarction phase （2-4 hours post-infarction）, a mixed edema was observed. After reperfusion, there was a mild improvement in cell edema, while the angioedema became more serious. A high DWI signal and a low apparent diffusion coefficient signal were observed, and some rats showed high T2WI and T2FLAIR signals. For the late cerebral infarction phase （4-6 hours post-infarction）, significant angioedema was visible in the infarction site. After reperfusion, there was a significant increase in angioedema, while there was evidence of hemorrhage and necrosis. A mixed signal was observed on DWI, while a high apparent diffusion coefficient signal, a high T2WI signal, and a high T2FLAIR signal were also observed. All 86 cerebral infarction patients were subjected to T2WI, T2FLAIR, and DWI. MRI results of clinic data similar to the early infarction phase of animal experiments were found in 51 patients, for which 10 patients （10/51） had an onset time greater than 6 hours. A total of 35 patients had MRI results similar to the middle and late infarction phase of animal experiments, of which eight patients （8/35） had an onset time less than 6 hours. These data suggest that defining the ＂therapeutic time window＂ as the time 6 hours after infarction may not be suitable for all patients. Integrated application of MRI sequences including T2WI, T2FLAIR, DW-MRI, and apparent diffusion coefficient mapping should be used to examine the ischemic penumbra, which may provide valuable information for identifying the ＂therapeutic time window＂.展开更多
Impaired structure and function of the hippocampus is a valuable predictor of progression from amnestic mild cognitive impairment（a MCI） to Alzheimer＇s disease（AD）. As a part of the medial temporal lobe memory sy...Impaired structure and function of the hippocampus is a valuable predictor of progression from amnestic mild cognitive impairment（a MCI） to Alzheimer＇s disease（AD）. As a part of the medial temporal lobe memory system,the hippocampus is one of the brain regions affected earliest by AD neuropathology,and shows progressive degeneration as a MCI progresses to AD. Currently,no validated biomarkers can precisely predict the conversion from a MCI to AD. Therefore,there is a great need of sensitive tools for the early detection of AD progression. In this review,we summarize the specifi c structural and functional changes in the hippocampus from recent a MCI studies using neurophysiological and neuroimaging data. We suggest that a combination of advanced multi-modal neuroimaging measures in discovering biomarkers will provide more precise and sensitive measures of hippocampal changes than using only one of them. These will potentially affect early diagnosis and disease-modifying treatments. We propose a new sequential and progressive framework in which the impairment spreads from the integrity of fibers to volume and then to function in hippocampal subregions. Meanwhile,this is likely to be accompanied by progressive impairment of behavioral and neuropsychological performance in the progression of a MCI to AD.展开更多
Restorative cell-based therapies for experimental brain injury, such as stroke and traumatic brain injury,substantially improve functional outcome. We discuss and review state of the art magnetic resonance imaging met...Restorative cell-based therapies for experimental brain injury, such as stroke and traumatic brain injury,substantially improve functional outcome. We discuss and review state of the art magnetic resonance imaging methodologies and their applications related to cell-based treatment after brain injury. We focus on the potential of magnetic resonance imaging technique and its associated challenges to obtain useful new information related to cell migration, distribution, and quantitation, as well as vascular and neuronal remodeling in response to cell-based therapy after brain injury. The noninvasive nature of imaging might more readily help with translation of cell-based therapy from the laboratory to the clinic.展开更多
The rhesus macaque(Macaca mulatta)is a crucial experimental animal that shares many genetic,brain organizational,and behavioral characteristics with humans.A macaque brain atlas is fundamental to biomedical and evolut...The rhesus macaque(Macaca mulatta)is a crucial experimental animal that shares many genetic,brain organizational,and behavioral characteristics with humans.A macaque brain atlas is fundamental to biomedical and evolutionary research.However,even though connectivity is vital for understanding brain functions,a connectivity-based whole-brain atlas of the macaque has not previously been made.In this study,we created a new whole-brain map,the Macaque Brainnetome Atlas(MacBNA),based on the anatomical connectivity profiles provided by high angular and spatial resolution ex vivo diffusion MRI data.The new atlas consists of 248 cortical and 56 subcortical regions as well as their structural and functional connections.The parcellation and the diffusion-based tractography were evaluated with invasive neuronal-tracing and Nissl-stained images.As a demonstrative application,the structural connectivity divergence between macaque and human brains was mapped using the Brainnetome atlases of those two species to uncover the genetic underpinnings of the evolutionary changes in brain structure.The resulting resource includes:(1)the thoroughly delineated Macaque Brainnetome Atlas(MacBNA),(2)regional connectivity profiles,(3)the postmortem high-resolution macaque diffusion and T2-weighted MRI dataset(Brainnetome-8),and(4)multi-contrast MRI,neuronal-tracing,and histological images collected from a single macaque.MacBNA can serve as a common reference frame for mapping multifaceted features across modalities and spatial scales and for integrative investigation and characterization of brain organization and function.Therefore,it will enrich the collaborative resource platform for nonhuman primates and facilitate translational and comparative neuroscience research.展开更多
Objective To develop and test an image fusion software(fDf,fMRI/DTI fusion) which can overlap the anatomical(T1WI images),functional MRI(fMRI) and diffusion tensor imaging(DTI) simultaneously for preoperational evalua...Objective To develop and test an image fusion software(fDf,fMRI/DTI fusion) which can overlap the anatomical(T1WI images),functional MRI(fMRI) and diffusion tensor imaging(DTI) simultaneously for preoperational evaluation of patients′ tumor.Methods fMRI with bilateral hands grasp movement and DTI were performed using GE 1.5 T magnetic resonance system on 10 subjects(5 healthy volunteers and 5 patients with brain tumor,of which 3 were metastases,1 was cavernous hemangioma and 1 was glioma).All data were input to the personal computer and offline postprocessing of fMRI and DTI data was performed using SPM5 and VolumeOne software package to visualize the activated functional cortex areas and corticospinal tracts.fDf was used to import the fMRI and structural images to VolumeOne to show them simultaneously.Results Brain functional activation maps and diffusion tensor fiber tracking images were obtained in all five healthy volunteers and four patients except one who suffered from left hemiplegia.The functional activation maps and the fiber tracking images were successfully fused by the fDf software,where the activations areas and the white matter fiber were displayed together.The fusion images of healthy volunteers showed the hand motion areas and corresponding corticospinal tracts,while that of the patients display the relationship of the eloquent cortex and peritumoral fiber tracts,which were useful in guiding the treatments for the surgeons and radiotherapists.It only took hours to present the fused images to the neurosurgeons or the radiotherapists.Conclusions All the results confirm that the image fusion software work well for all the data.It is an easy,free and fast way to realize the image fusion.The neurosurgeon and radiotherapist consider the software were very helpful for preoperative planning.展开更多
Background Degeneration of the locus coeruleus(LC)noradrenergic system contributes to clinical symptoms in Alzheimer’s disease(AD)and Parkinson’s disease(PD).Diffusion magnetic resonance imaging(MRI)has the potentia...Background Degeneration of the locus coeruleus(LC)noradrenergic system contributes to clinical symptoms in Alzheimer’s disease(AD)and Parkinson’s disease(PD).Diffusion magnetic resonance imaging(MRI)has the potential to evaluate the integrity of the LC noradrenergic system.The aim of the current study was to determine whether the diffusion MRI-measured integrity of the LC and its tracts are sensitive to noradrenergic degeneration in AD and PD.Methods Post-mortem in situ T1-weighted and multi-shell diffusion MRI was performed for 9 AD,14 PD,and 8 control brain donors.Fractional anisotropy(FA)and mean diffusivity were derived from the LC,and from tracts between the LC and the anterior cingulate cortex,the dorsolateral prefrontal cortex(DLPFC),the primary motor cortex(M1)or the hippocampus.Brain tissue sections of the LC and cortical regions were obtained and immunostained for dopamine-beta hydroxylase(DBH)to quantify noradrenergic cell density and fiber load.Group comparisons and correlations between outcome measures were performed using linear regression and partial correlations.Results The AD and PD cases showed loss of LC noradrenergic cells and fibers.In the cortex,the AD cases showed increased DBH+immunoreactivity in the DLPFC compared to PD cases and controls,while PD cases showed reduced DBH+immunoreactivity in the M1 compared to controls.Higher FA within the LC was found for AD,which was correlated with loss of noradrenergic cells and fibers in the LC.Increased FA of the LC-DLPFC tract was correlated with LC noradrenergic fiber loss in the combined AD and control group,whereas the increased FA of the LC-M1 tract was correlated with LC noradrenergic neuronal loss in the combined PD and control group.The tract alterations were not correlated with cortical DBH+immunoreactivity.Conclusions In AD and PD,the diffusion MRI-detected alterations within the LC and its tracts to the DLPFC and the M1 were associated with local noradrenergic neuronal loss within the LC,rather than noradrenergic changes in the cortex.展开更多
Attention-deficit/hyperactivity disorder(ADHD)has been conceptualized as a brain dysconnectivity disorder.In the past decade,noninvasive diffusion magnetic resonance imaging(dMRI)studies have demonstrated that individ...Attention-deficit/hyperactivity disorder(ADHD)has been conceptualized as a brain dysconnectivity disorder.In the past decade,noninvasive diffusion magnetic resonance imaging(dMRI)studies have demonstrated that individuals with ADHD have alterations in the white matter structural connectome,and that these alterations are associated with core symptoms and cognitive deficits in patients.This review aims to summarize recent dMRI-based structural connectome studies in ADHD from voxel-,tractography-,and network-based perspectives.Voxel-and tractography-based studies have demonstrated disrupted microstructural properties predominantly located in the frontostriatal tracts,the corpus callosum,the corticospinal tracts,and the cingulum bundle in patients with ADHD.Network-based studies have suggested abnormal global and local efficiency as well as nodal properties in the prefrontal and parietal regions in the ADHD structural connectomes.The altered structural connectomes in those with ADHD provide significant signatures for prediction of symptoms and diagnostic classification.These studies suggest that abnormalities in the structural connectome may be one of the neural underpinnings of ADHD psychopathology and show potential for establishing imaging biomarkers in clinical evaluation.However,given that there are inconsistent findings across studies due to sample heterogeneity and analysis method variations,these ADHD-related white matter alterations are still far from informing clinical practice.Future studies with larger and more homogeneous samples are needed to validate the consistency of current results;advanced dMRI techniques can help to generatemuchmore precise estimation of whitematter pathways and assure specific fiber configurations;and finally,dimensional analysis frameworks can deepen our understanding of the neurobiology underlying ADHD.展开更多
基金supported in part by the High Magnetic Field Laboratory(NHMFL)and Advanced Magnetic Resonance Imaging and Spectroscopy(AMRIS)under Magnetic Laboratory Visiting Scientist Program Award,No.VSP#327(to RG)。
文摘During the last decades,advances in the understanding of genetic,cellular,and microstructural alterations associated to Huntington's disease(HD)have improved the understanding of this progressive and fatal illness.However,events related to early neuropathological events,neuroinflammation,deterioration of neuronal connectivity and compensatory mechanisms still remain vastly unknown.Ultra-high field diffusion MRI(UHFD-MRI)techniques can contribute to a more comprehensive analysis of the early microstructural changes observed in HD.In addition,it is possible to evaluate if early imaging microstructural parameters might be linked to histological biomarkers.Moreover,qualitative studies analyzing histological complexity in brain areas susceptible to neurodegeneration could provide information on inflammatory events,compensatory increase of neuroconnectivity and mechanisms of brain repair and regeneration.The application of ultra-high field diffusion-MRI technology in animal models,particularly the R6/1 mice(a common preclinical mammalian model of HD),provide the opportunity to analyze alterations in a physiologically intact model of the disease.Although some disparities in volumetric changes across different brain structures between preclinical and clinical models has been documented,further application of different diffusion MRI techniques used in combination like diffusion tensor imaging,and neurite orientation dispersion and density imaging have proved effective in characterizing early parameters associated to alteration in water diffusion exchange within intracellular and extracellular compartments in brain white and grey matter.Thus,the combination of diffusion MRI imaging techniques and more complex neuropathological analysis could accelerate the discovery of new imaging biomarkers and the early diagnosis and neuromonitoring of patients affected with HD.
基金This work was supported by the Natural Science Foundation of Heilongjiang Province(LH2021F046).
文摘Diffusion MRI is an important technology for detecting human brain nerve pathways,aiding in neuroscience and clinical diagnosis.However,the Multi-ShellMulti-TissueConstrainedSphericalDeconvolution(M-CSD)method,which is a significant technique for reconstructing thefibre orientation distribution func-tion(fODF),requires multishell data with a considerable number of gradient direc-tions to achieve high accuracy.As multishell data are not easy to acquire,the Single-Shell Single-Tissue CSD(S-CSD)suffers from the Partial Volume Effect(PVE).It would be more convenient if we could use single-shell data to reconstruct better fODFs.We propose a novel method that utilizes the spatial structure and anisotropy of dMRI data through a spherical convolution network.We reduce the need for high-quality data by utilizing b=1000 s/mm2 with 60 gradient directions or even less.Our results show that our method outperforms the traditional S-CSD when compared to the M-CSD results as our gold standard.
文摘Objective To evaluate the value of MRI diffusion weighted imaging in localization of prostate cancer with whole-mount step section pathology. Methods We treated 36 patients using laparoscopic radical prostatectomy from Oct. 2009 to Jun. 2010. Patients who did not have an MRL /DWI examination or a surgical history of pros-
基金supported by the Eunice Kennedy Shriver National Institute of Child Health and Human Development.VJW acknowledges additional supported by NIGMS grant(K99 GM140338-01)for this work.
文摘Nuclear magnetic resonance(NMR)measurements of water diffusion have been extensively used to probe microstructure in porous materials,such as biological tissue,however primarily using pulsed gradient spin echo(PGSE)methods.Low-field single-sided NMR systems have built-in static gradients(SG)much stronger than typical PGSE maximum gradient strengths,which allows for the signal attenuation at extremely high b-values to be explored.Here,we perform SG spin echo(SGSE)and SG stimulated echo(SGSTE)diffusion measurements on biological cells,tissues,and gels.Measurements on fixed and live neonatal mouse spinal cord,lobster ventral nerve cord,and starved yeast cells all show multiexponential signal attenuation on a scale of b with significant signal fractions observed at b×Do>1 with b as high as 400 ms/um2.These persistent signal fractions trend with surface-to-volume ratios for these systems,as expected from porous media theory.An exception found for the case of fixed vs.live spinal cords was attributed to faster exchange or permeability in live spinal cords than in fixed spinal cords on the millisecond timescale.Data suggests the existence of multiple exchange processes in neural tissue,which may be relevant to the modeling of time-dependent diffusion in gray matter.The observed multi-exponential attenuation is from protons on water and not macromolecules because it remains proportional to the normalized signal when a specimen is washed with D20.The signal that persists to b×Do>1 is also drastically reduced after delipidation,indicating that it originates from lipid membranes that restrict water diffusion.The multiexponential or stretched exponential character of the signal attenuation at b×Do>1 appears mono-exponential when viewed on a scale of(b×Do)/3,suggesting it may originate from localization or motional averaging of water near membranes on sub-micron length scales.To try to disambiguate these two contributions,signal attenuation curves were compared at varying temperatures.While the curves align when normalizing them using the localization length scale,they separate on a motional averaging length scale.This supports localization as the source of non-Gaussian displacements,but this interpretation is still provisional due to the possible confounds of heterogeneity,exchange,and relaxation.Measurements on two types of gel phantoms designed to mimic extracellular matrix.one with charged functional groups synthesized from polyacrylic acid(PAC)and another with uncharged functional groups synthesized from polyacrylamide(PAM),both exhibit signal at b×Do>1,potentially due to water interacting with macromolecules.These preliminary finding motivate future research into contrast and attenuation mechanisms in tissue with low-field,high-gradient NMR。
基金National Natural Science Foundation of China,Grant/Award Numbers:61901465,82371910。
文摘Background:Ultra high field diffusion magnetic resonance imaging(dMRI)provides diffusion-weighted(DW)images with a high signal-to-noise ratio,but increases inhomogeneity,which affects the accuracy of dMRI metric recon-struction.Current methods for correcting inhomogeneity rarely consider the accuracy of the reconstructed dMRI metrics.Deep learning models for reconstructing metrics from dMRI signals typically assume that DW images have a homogeneous intensity.To address these challenges,we propose a deep learning model capable of directly reconstructing high-accuracy dMRI metric maps from inhomogeneous DW images.Methods:An attention-based q-space inhomogeneity-resistant reconstruction network(qIRR-Net)is proposed for the voxel-wise reconstruction of diffusion tensor imaging and diffusion kurtosis imaging metrics.A training procedure based on data augmentation and consistency loss is introduced to ensure that the reconstruction results of qIRR-Net are not affected by signal in-homogeneity.The 3T and 7T dMRI data from the Human Connectome Project are used for model training,testing,and evaluation.Results:On the 3T dMRI data with simulated inhomogeneity,qIRR-Net improves the peak signal-to-noise ratio by 5.39 and the structural similarity index measure by 0.18 compared with weighted linear least-squares fitting.On the 7T dMRI data,the metric maps reconstructed by qIRR-Net not only exhibit clearer tissue structures but also demonstrate greater stability compared with the weighted linear least-squares results.Conclusions:The proposed qIRR-Net enables the accurate reconstruction of dMRI metrics from inhomogeneous DW images.This approach could poten-tially be expanded to obtain multiple artifact-free metric maps from ultrahigh field dMRI for neuroscience research and neurology applications.
基金Supported by the Research Project of Dongguan Higher Education (200910815252)the Beijing Natural Science Foundation(7102102)the Scientific Research Key Program of Beijing Municipal Commission of Ed-ucation(KZ200810025011)~~
文摘To evaluate the effect of the positive-indefinite matrix on the diffusion tensor-derived parameters, a modified algorithm is proposed for calculating these parameters. Magnetic resonance （MR） diffusion tensor images of five healthy volunteers are collected. The diffusion sensitive gradient magnetic fields are applied along 25 directions and the diffusion weighting value is 1 000 s/mm^2. Many positive-indefinite diffusion tensors can be found in the white matter area, such as the genu and the splenium of corpus callosum. Due to the positive-indefinite matrix, the mean diffusivity （MD） and the fractional anisotropy （FA） are under-estimated and over-estimated by using the conventional algorithm. Thus, the conventional algorithm is modified by using the absolute values of all eigenvalues. Results show that both the robustness and the reliability for deriving these parameters are improved by the modified algorithm.
基金the Swedish Foundation for International Cooperation in Research and Higher Education(STINT),and the Swedish Research Council(Dnr 2022e04715).
文摘Water exchange between the different compartments of a heterogeneous specimen can be characterized via diffusion magnetic resonance imaging(dMRI).Many analysis frameworks using dMRI data have been proposed to describe exchange,often using a double diffusion encoding(DDE)stimulated echo sequence.Techniques such as diffusion exchange weighted imaging(DEWI)and the filter exchange and rapid exchange models,use a specific subset of the full space DDE signal.In this work,a general representation of the DDE signal was employed with different sampling schemes(namely constant b1,diagonal and anti-diagonal)from the data reduction models to estimate exchange.A near-uniform sampling scheme was proposed and compared with the other sampling schemes.The filter exchange and rapid exchange models were also applied to estimate exchange with their own subsampling schemes.These subsampling schemes and models were compared on both simulated data and experimental data acquired with a benchtop MR scanner.In synthetic data,the diagonal and near-uniform sampling schemes performed the best due to the consistency of their estimates with the ground truth.In experimental data,the shifted diagonal and near-uniform sampling schemes outperformed the others,yielding the most consistent estimates with the full space estimation.The results suggest the feasibility of measuring exchange using a general representation of the DDE signal along with variable sampling schemes.In future studies,algorithms could be further developed for the optimization of sampling schemes,as well as incorporating additional properties,such as geometry and diffusion anisotropy,into exchange frameworks.
文摘Searching for effective biomarkers is one of the most challenging tasks in the research ？eld of Autism Spectrum Disorder（ASD）. Magnetic resonance imaging（MRI） provides a non-invasive and powerful tool for investigating changes in the structure, function, maturation,connectivity, and metabolism of the brain of children with ASD. Here, we review the more recent MRI studies in young children with ASD, aiming to provide candidate biomarkers for the diagnosis of childhood ASD. The review covers structural imaging methods, diffusion tensor imaging, resting-state functional MRI, and magnetic resonance spectroscopy. Future advances in neuroimaging techniques, as well as cross-disciplinary studies and largescale collaborations will be needed for an integrated approach linking neuroimaging, genetics, and phenotypic data to allow the discovery of new, effective biomarkers.
文摘Traumatic brain injury is a major cause of death and disability. This is a brief report based on a symposium presentation to the 2014 Chinese Neurotrauma Association Meeting in San Francisco, USA. It covers the work from our laboratory in applying multimodal MRI to study experimental traumatic brain injury in rats with comparisons made to behavioral tests and histology. MRI protocols include structural, perfusion, manganese-enhanced, diffusion-tensor MRI, and MRI of blood-brain barrier integrity and cerebrovascular reactivity.
基金funded by Sweden's Innovation Agency(VINNOVA)ASSIST,Analytic Imaging Diagnostic Arena(AIDA),Swedish Foundation for Strategic Research(RMX18-0056)Linkoping University Center for Industrial Information Technology(CENIIT),LiU Cancer Barncancerfonden,and a research grant(00028384)from VILLUM FONDEN。
文摘Q-space trajectory imaging(QTI)allows non-invasive estimation of microstructural features of heterogeneous porous media via diffusion magnetic resonance imaging performed with generalised gradient waveforms.A recently proposed constrained estimation framework,called QTI+,improved QTI's resilience to noise and data sparsity,thus increasing the reliability of the method by enforcing relevant positivity constraints.In this work we consider expanding the set of constraints to be applied during the fitting of the QTI model.We show that the additional conditions,which introduce an upper bound on the diffusivity values,further improve the retrieved parameters on a publicly available human brain dataset as well as on data acquired from healthy volunteers using a scanner-ready protocol.
基金supported by the National Natural Science Foundation of China(82371507 and 82090034)Outstanding Youth Fund for Universities in Anhui Province(2024AH020004)+5 种基金the collaborative innovation project between universities and Hefei Comprehensive National Science Center(GXXT-2022-028)the Hefei Comprehensive National Science Center Hefei Brain Project,the 2021 Anhui Province Key R&D Project:Population Health Special Project(202104j07020033)major project of Research Fund of Anhui Institute of Translational Medicine in 2020(2020zhyx A04)the Anhui Province Clinical Medical Research Transformation Special Project(202204295107020006 and 202204295107020028)National Institutes of Health grant(R01 NS113832 and R01 NS129855)National Research and Engineering Council Canada,Discovery Grant。
文摘White matter(WM)comprises approximately half of the human brain volume and is primarily composed of bundles of axons and glia.The axons conduct nerve impulses between gray matter(GM)to support information transmission and coordination within brain networks or circuits.Despite the overwhelming emphasis of human brain imaging on GM,few would deny the importance of the functional contributions of WM to human cognition and behavior.For in vivo brain studies,diffusion magnetic resonance imaging(MRI)has been widely used to delineate WM fibers and measure their microstructural properties,but diffusion MRI reveals little about functional activity.For a long time,we have lacked an in vivo way to quantify functional metrics of wM.In contrast to the widespread application of functional MRI(fMRI)based on blood oxygenation-level-dependent(BOLD)signals to assess GM functions[1],BOLD effects in WM have been regarded as noise or nuisance variables in most neuroimaging studies.
基金supported by the National Natural Science Foundation of China,No.30960399,and No.81160181
文摘In this study, we established a Wistar rat model of right middle cerebral artery occlusion and observed pathological imaging changes （T2-weighted imaging [T2WI], T2FLAIR, and diffusion-weighted imaging [DWI]） following cerebral infarction. The pathological changes were divided into three phases： early cerebral infarction, middle cerebral infarction, and late cerebral infarction. In the early cerebral infarction phase （less than 2 hours post-infarction）, there was evidence of intracellular edema, which improved after reperfusion. This improvement was defined as the ischemic penumbra. In this phase, a high DWI signal and a low apparent diffusion coefficient were observed in the right basal ganglia region. By contrast, there were no abnormal T2WI and T2FLAIR signals. For the middle cerebral infarction phase （2-4 hours post-infarction）, a mixed edema was observed. After reperfusion, there was a mild improvement in cell edema, while the angioedema became more serious. A high DWI signal and a low apparent diffusion coefficient signal were observed, and some rats showed high T2WI and T2FLAIR signals. For the late cerebral infarction phase （4-6 hours post-infarction）, significant angioedema was visible in the infarction site. After reperfusion, there was a significant increase in angioedema, while there was evidence of hemorrhage and necrosis. A mixed signal was observed on DWI, while a high apparent diffusion coefficient signal, a high T2WI signal, and a high T2FLAIR signal were also observed. All 86 cerebral infarction patients were subjected to T2WI, T2FLAIR, and DWI. MRI results of clinic data similar to the early infarction phase of animal experiments were found in 51 patients, for which 10 patients （10/51） had an onset time greater than 6 hours. A total of 35 patients had MRI results similar to the middle and late infarction phase of animal experiments, of which eight patients （8/35） had an onset time less than 6 hours. These data suggest that defining the ＂therapeutic time window＂ as the time 6 hours after infarction may not be suitable for all patients. Integrated application of MRI sequences including T2WI, T2FLAIR, DW-MRI, and apparent diffusion coefficient mapping should be used to examine the ischemic penumbra, which may provide valuable information for identifying the ＂therapeutic time window＂.
基金supported by the National Natural Science Foundation of China (91332000,81171021,and 91132727)the Key Program for Clinical Medicine and Science and Technology,Jiangsu Provence,China ( BL2013025 and BL2014077)
文摘Impaired structure and function of the hippocampus is a valuable predictor of progression from amnestic mild cognitive impairment（a MCI） to Alzheimer＇s disease（AD）. As a part of the medial temporal lobe memory system,the hippocampus is one of the brain regions affected earliest by AD neuropathology,and shows progressive degeneration as a MCI progresses to AD. Currently,no validated biomarkers can precisely predict the conversion from a MCI to AD. Therefore,there is a great need of sensitive tools for the early detection of AD progression. In this review,we summarize the specifi c structural and functional changes in the hippocampus from recent a MCI studies using neurophysiological and neuroimaging data. We suggest that a combination of advanced multi-modal neuroimaging measures in discovering biomarkers will provide more precise and sensitive measures of hippocampal changes than using only one of them. These will potentially affect early diagnosis and disease-modifying treatments. We propose a new sequential and progressive framework in which the impairment spreads from the integrity of fibers to volume and then to function in hippocampal subregions. Meanwhile,this is likely to be accompanied by progressive impairment of behavioral and neuropsychological performance in the progression of a MCI to AD.
基金supported by NIH grants RO1 NS64134 and RO1 NS 48349
文摘Restorative cell-based therapies for experimental brain injury, such as stroke and traumatic brain injury,substantially improve functional outcome. We discuss and review state of the art magnetic resonance imaging methodologies and their applications related to cell-based treatment after brain injury. We focus on the potential of magnetic resonance imaging technique and its associated challenges to obtain useful new information related to cell migration, distribution, and quantitation, as well as vascular and neuronal remodeling in response to cell-based therapy after brain injury. The noninvasive nature of imaging might more readily help with translation of cell-based therapy from the laboratory to the clinic.
基金partially supported by the Science and Technology Innovation 2030-Brain Science and Brain-Inspired Intelligence Project(2021ZD0200200)the National Natural Science Foundation of China(62327805,82151307,82072099,82202253)。
文摘The rhesus macaque(Macaca mulatta)is a crucial experimental animal that shares many genetic,brain organizational,and behavioral characteristics with humans.A macaque brain atlas is fundamental to biomedical and evolutionary research.However,even though connectivity is vital for understanding brain functions,a connectivity-based whole-brain atlas of the macaque has not previously been made.In this study,we created a new whole-brain map,the Macaque Brainnetome Atlas(MacBNA),based on the anatomical connectivity profiles provided by high angular and spatial resolution ex vivo diffusion MRI data.The new atlas consists of 248 cortical and 56 subcortical regions as well as their structural and functional connections.The parcellation and the diffusion-based tractography were evaluated with invasive neuronal-tracing and Nissl-stained images.As a demonstrative application,the structural connectivity divergence between macaque and human brains was mapped using the Brainnetome atlases of those two species to uncover the genetic underpinnings of the evolutionary changes in brain structure.The resulting resource includes:(1)the thoroughly delineated Macaque Brainnetome Atlas(MacBNA),(2)regional connectivity profiles,(3)the postmortem high-resolution macaque diffusion and T2-weighted MRI dataset(Brainnetome-8),and(4)multi-contrast MRI,neuronal-tracing,and histological images collected from a single macaque.MacBNA can serve as a common reference frame for mapping multifaceted features across modalities and spatial scales and for integrative investigation and characterization of brain organization and function.Therefore,it will enrich the collaborative resource platform for nonhuman primates and facilitate translational and comparative neuroscience research.
文摘Objective To develop and test an image fusion software(fDf,fMRI/DTI fusion) which can overlap the anatomical(T1WI images),functional MRI(fMRI) and diffusion tensor imaging(DTI) simultaneously for preoperational evaluation of patients′ tumor.Methods fMRI with bilateral hands grasp movement and DTI were performed using GE 1.5 T magnetic resonance system on 10 subjects(5 healthy volunteers and 5 patients with brain tumor,of which 3 were metastases,1 was cavernous hemangioma and 1 was glioma).All data were input to the personal computer and offline postprocessing of fMRI and DTI data was performed using SPM5 and VolumeOne software package to visualize the activated functional cortex areas and corticospinal tracts.fDf was used to import the fMRI and structural images to VolumeOne to show them simultaneously.Results Brain functional activation maps and diffusion tensor fiber tracking images were obtained in all five healthy volunteers and four patients except one who suffered from left hemiplegia.The functional activation maps and the fiber tracking images were successfully fused by the fDf software,where the activations areas and the white matter fiber were displayed together.The fusion images of healthy volunteers showed the hand motion areas and corresponding corticospinal tracts,while that of the patients display the relationship of the eloquent cortex and peritumoral fiber tracts,which were useful in guiding the treatments for the surgeons and radiotherapists.It only took hours to present the fused images to the neurosurgeons or the radiotherapists.Conclusions All the results confirm that the image fusion software work well for all the data.It is an easy,free and fast way to realize the image fusion.The neurosurgeon and radiotherapist consider the software were very helpful for preoperative planning.
文摘Background Degeneration of the locus coeruleus(LC)noradrenergic system contributes to clinical symptoms in Alzheimer’s disease(AD)and Parkinson’s disease(PD).Diffusion magnetic resonance imaging(MRI)has the potential to evaluate the integrity of the LC noradrenergic system.The aim of the current study was to determine whether the diffusion MRI-measured integrity of the LC and its tracts are sensitive to noradrenergic degeneration in AD and PD.Methods Post-mortem in situ T1-weighted and multi-shell diffusion MRI was performed for 9 AD,14 PD,and 8 control brain donors.Fractional anisotropy(FA)and mean diffusivity were derived from the LC,and from tracts between the LC and the anterior cingulate cortex,the dorsolateral prefrontal cortex(DLPFC),the primary motor cortex(M1)or the hippocampus.Brain tissue sections of the LC and cortical regions were obtained and immunostained for dopamine-beta hydroxylase(DBH)to quantify noradrenergic cell density and fiber load.Group comparisons and correlations between outcome measures were performed using linear regression and partial correlations.Results The AD and PD cases showed loss of LC noradrenergic cells and fibers.In the cortex,the AD cases showed increased DBH+immunoreactivity in the DLPFC compared to PD cases and controls,while PD cases showed reduced DBH+immunoreactivity in the M1 compared to controls.Higher FA within the LC was found for AD,which was correlated with loss of noradrenergic cells and fibers in the LC.Increased FA of the LC-DLPFC tract was correlated with LC noradrenergic fiber loss in the combined AD and control group,whereas the increased FA of the LC-M1 tract was correlated with LC noradrenergic neuronal loss in the combined PD and control group.The tract alterations were not correlated with cortical DBH+immunoreactivity.Conclusions In AD and PD,the diffusion MRI-detected alterations within the LC and its tracts to the DLPFC and the M1 were associated with local noradrenergic neuronal loss within the LC,rather than noradrenergic changes in the cortex.
基金supported by the National Natural Science Foundation of China(Nos.82021004,81620108016,31221003)Changjiang Scholar Professorship Award(No.T2015027).
文摘Attention-deficit/hyperactivity disorder(ADHD)has been conceptualized as a brain dysconnectivity disorder.In the past decade,noninvasive diffusion magnetic resonance imaging(dMRI)studies have demonstrated that individuals with ADHD have alterations in the white matter structural connectome,and that these alterations are associated with core symptoms and cognitive deficits in patients.This review aims to summarize recent dMRI-based structural connectome studies in ADHD from voxel-,tractography-,and network-based perspectives.Voxel-and tractography-based studies have demonstrated disrupted microstructural properties predominantly located in the frontostriatal tracts,the corpus callosum,the corticospinal tracts,and the cingulum bundle in patients with ADHD.Network-based studies have suggested abnormal global and local efficiency as well as nodal properties in the prefrontal and parietal regions in the ADHD structural connectomes.The altered structural connectomes in those with ADHD provide significant signatures for prediction of symptoms and diagnostic classification.These studies suggest that abnormalities in the structural connectome may be one of the neural underpinnings of ADHD psychopathology and show potential for establishing imaging biomarkers in clinical evaluation.However,given that there are inconsistent findings across studies due to sample heterogeneity and analysis method variations,these ADHD-related white matter alterations are still far from informing clinical practice.Future studies with larger and more homogeneous samples are needed to validate the consistency of current results;advanced dMRI techniques can help to generatemuchmore precise estimation of whitematter pathways and assure specific fiber configurations;and finally,dimensional analysis frameworks can deepen our understanding of the neurobiology underlying ADHD.
