Chunlei Liu

Duke University Medical Center, Durham, North Carolina, United States

Are you Chunlei Liu?

Claim your profile

Publications (49)177.34 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Quantitative susceptibility mapping (QSM) is a novel MRI method for quantifying tissue's magnetic property. In the brain, it reflects the molecular composition and microstructure of the local tissue. However, susceptibility maps reconstructed from single-orientation data still suffer from streaking artifacts which obscure structural details and small lesions. We propose and have developed a general method for estimating streaking artifacts and subtracting them from susceptibility maps. Specifically, this method uses a sparse linear equations and least-squares (LSQR)-algorithm-based method to derive an initial estimation of magnetic susceptibility, a fast quantitative susceptibility mapping method to estimate the susceptibility boundaries, and an iterative approach to estimate the susceptibility artifact from ill-conditioned k-space regions only. With a fixed set of parameters for the initial susceptibility estimation and subsequent streaking artifact estimation and removal, the method provides an unbiased estimate of tissue susceptibility with negligible streaking artifacts, as compared to multi-orientation QSM reconstruction. This method allows improved delineation of white matter lesions in patients with multiple sclerosis and small structures of the human brain with excellent anatomical details. The proposed methodology can be extended to other existing QSM algorithms. Copyright © 2014. Published by Elsevier Inc.
    NeuroImage 12/2014; 108. · 6.13 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Cranial irradiation is a standard therapy for primary and metastatic brain tumors. A major drawback of radiotherapy (RT), however, is long-term cognitive loss that affects quality of life. Radiation-induced oxidative stress in normal brain tissue is thought to contribute to cognitive decline. We evaluated the effectiveness of a novel mimic of superoxide dismutase enzyme (SOD), MnTnBuOE-2-PyP5+( Mn(III) meso-tetrakis(N-n-butoxyethylpyridinium-2-yl)porphyrin) to provide long-term neuroprotection following 8 Gray of whole brain irradiation. Long-term RT damage can only be assessed by brain imaging and neurocognitive studies. C57BL/6J mice were treated with MnTnBuOE-2-PyP5+ pre- and post-RT and evaluated three months later. At this time point, drug concentration in the brain was 25 nM. Mice treated with MnTnBuOE-2-PyP5+/RT exhibited MRI evidence for myelin preservation in the corpus callosum compared with saline/RT treatment. Corpus callosum histology demonstrated a significant loss of axons in the saline/RT group that was rescued in the MnTnBuOE-2-PyP5+/RT group. Additionally, the saline/RT groups exhibited deficits in motor proficiency as assessed by the rotorod test and running wheel tests. These deficits were ameliorated in groups treated with MnTnBuOE-2-PyP5+/RT. Our data demonstrate that MnTnBuOE-2-PyP5+ is neuroprotective for oxidative stress damage caused by radiation exposure. Additionally, glioblastoma cells were not protected by MnTnBuOE-2-PyP5+ combination with radiation in vitro. Likewise, the combination of MnTnBuOE-2-PyP5+ with radiation prolonged tumor growth more than RT alone in flank tumors. In summary, MnTnBuOE-2-PyP5+ has dual activity as a neuroprotector and a tumor radiosensitizer. Thus, it is an attractive candidate for adjuvant therapy with RT in future studies with brain cancer patients.
    Molecular Cancer Therapeutics 10/2014; · 5.60 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In the human brain, iron is more prevalent in gray matter than in white matter, and deep gray matter structures, particularly the globus pallidus, putamen, caudate nucleus, substantia nigra, red nucleus, and dentate nucleus, exhibit especially high iron content. Abnormally elevated iron levels have been found in various neurodegenerative diseases. Additionally, iron overload and related neurodegeneration may also occur during aging, but the functional consequences are not clear. In this study, we explored the correlation between magnetic susceptibility - a surrogate marker of brain iron - of these gray matter structures with behavioral measures of motor and cognitive ability, in 132 healthy adults aged 40-83 years. Latent variables corresponding to manual dexterity and executive functions were obtained using factor analysis. The factor scores for manual dexterity declined significantly with increasing age. Independent of gender, age, and global cognitive function, increasing magnetic susceptibility in the globus pallidus and red nuclei was associated with decreasing manual dexterity. This finding suggests the potential value of magnetic susceptibility, a non-invasive quantitative imaging marker of iron, for the study of iron-related brain function changes.
    NeuroImage 10/2014; · 6.13 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Susceptibility-weighted imaging (SWI) is a magnetic resonance imaging (MRI) technique that enhances image contrast by using the susceptibility differences between tissues. It is created by combining both magnitude and phase in the gradient echo data. SWI is sensitive to both paramagnetic and diamagnetic substances which generate different phase shift in MRI data. SWI images can be displayed as a minimum intensity projection that provides high resolution delineation of the cerebral venous architecture, a feature that is not available in other MRI techniques. As such, SWI has been widely applied to diagnose various venous abnormalities. SWI is especially sensitive to deoxygenated blood and intracranial mineral deposition and, for that reason, has been applied to image various pathologies including intracranial hemorrhage, traumatic brain injury, stroke, neoplasm, and multiple sclerosis. SWI, however, does not provide quantitative measures of magnetic susceptibility. This limitation is currently being addressed with the development of quantitative susceptibility mapping (QSM) and susceptibility tensor imaging (STI). While QSM treats susceptibility as isotropic, STI treats susceptibility as generally anisotropic characterized by a tensor quantity. This article reviews the basic principles of SWI, its clinical and research applications, the mechanisms governing brain susceptibility properties, and its practical implementation, with a focus on brain imaging. J. Magn. Reson. Imaging 2014. © 2014 Wiley Periodicals, Inc.
    Journal of Magnetic Resonance Imaging 09/2014; · 2.57 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Prenatal alcohol exposure can result in long-term cognitive and behavioral deficits. Fetal alcohol spectrum disorder (FASD) refers to a range of permanent birth defects caused by prenatal alcohol exposure, and is the most common neurodevelopmental disorder in the US. Studies by autopsy and conventional structural MRI indicate that the midline structures of the brain are particularly vulnerable to prenatal alcohol exposure. Diffusion tensor imaging (DTI) has shown that abnormalities in brain white matter especially the corpus callosum are very common in FASD. Quantitative susceptibility mapping (QSM) is a novel technique that measures tissue's magnetic property. Such magnetic property is affected by tissue microstructure and molecular composition including that of myelin in the white matter. In this work, we studied three major white matter fiber bundles of a mouse model of FASD and compared it to control mice using both QSM and DTI. QSM revealed clear and significant abnormalities in anterior commissure, corpus callosum, and hippocampal commissure, which were likely due to reduced myelination. Our data also suggested that QSM may be even more sensitive than DTI for examining changes due to prenatal alcohol exposure. Although this is a preclinical study, the technique of QSM is readily translatable to human brain.
    NeuroImage 08/2014; · 6.13 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: PurposeThe purpose of this study was to determine whether susceptibility tensor imaging (STI) could overcome limitations of current techniques to detect tubules throughout the kidney.Methods Normal mouse kidneys (n = 4) were imaged at 9.4T using a three-dimensional gradient multi-echo sequence (55-micron isotropic resolution). Phase images from 12 orientations were obtained to compute the susceptibility tensor. Diffusion tensor imaging (DTI) with 12 encoding directions was compared with STI. Tractography was performed to visualize and track the course of tubules with DTI and STI. Confocal microscopy was used to identify which tubular segments of the nephron were detected by DTI and STI.ResultsDiffusion anisotropy was limited to the inner medulla of the kidney. DTI did not find a significant number of coherent tubular tracks in the outer medulla or cortex. With STI, we found strong susceptibility anisotropy and many tracks in the inner and outer medulla and in limited areas of the cortex.ConclusionSTI was able to track tubules throughout the kidney, whereas DTI was limited to the inner medulla. STI provides a novel contrast mechanism related to local tubule microstructure and may offer a powerful method to study the nephron. Magn Reson Med, 2014. © 2014 Wiley Periodicals, Inc.
    Magnetic Resonance in Medicine 04/2014; · 3.40 Impact Factor
  • Russell Dibb, Wei Li, Gary Cofer, Chunlei Liu
    [Show abstract] [Hide abstract]
    ABSTRACT: MR histology based on magnetic susceptibility can be used to visualize diamagnetic myelin (and its deterioration) in the central nervous system and is facilitated by the application of high magnetic field strengths and paramagnetic contrast agents. Characterizing the effect of these tools will aid in assessing white matter myelin content and microstructure. Image data from six gadolinium-perfused mouse brain specimens were acquired at 2.0, 7.0, and 9.4 Tesla. Magnetic susceptibility contrast was analyzed for its dependence on field strength, gadolinium concentration, and white matter fiber orientation. A model for this contrast is presented based on the three-pool model for white matter. The specimen data illustrate that white-gray matter susceptibility contrast is field strength independent. White-gray matter contrast improves significantly as a function of gadolinium contrast agent in the tissue, i.e., white matter appears increasingly more diamagnetic relative to gray matter. The simulated data from the model suggest that susceptibility anisotropy of white matter fiber bundles increases nonlinearly as a function of gadolinium concentration due to contrast agent compartmentalization into the extracellular white matter water pool. Using contrast agents in MR histology facilitates white-gray matter susceptibility contrast modulation and the probing of white matter microstructure and orientation. Magn Reson Med, 2014. © 2014 Wiley Periodicals, Inc.
    Magnetic Resonance in Medicine 01/2014; · 3.40 Impact Factor
  • Radiology 12/2013; · 6.21 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Quantitative susceptibility mapping (QSM) is a recently developed MRI technique that provides a quantitative measure of tissue magnetic susceptibility. To compute tissue magnetic susceptibilities based on gradient echoes, QSM requires reliable unwrapping of the measured phase images and removal of contributions caused by background susceptibilities. Typically, the two steps are performed separately. Here, we present a method that simultaneously performs phase unwrapping and HARmonic (background) PhasE REmovaL using the LAplacian operator (HARPERELLA). Both numerical simulations and in vivo human brain images show that HARPERELLA effectively removes both phase wraps and background phase, whilst preserving all low spatial frequency components originating from brain tissues. When compared with other QSM phase preprocessing techniques, such as path-based phase unwrapping followed by background phase removal, HARPERELLA preserves the tissue phase signal in gray matter, white matter and cerebrospinal fluid with excellent robustness, providing a convenient and accurate solution for QSM. The proposed algorithm is provided, together with QSM and susceptibility tensor imaging (STI) tools, in a shared software package named 'STI Suite'. Copyright © 2013 John Wiley & Sons, Ltd.
    NMR in Biomedicine 12/2013; 27(2). · 3.56 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: PURPOSE The hypothesis of the current study is that relationships between the structural connectome and cortical amyloid burden may provide complementary information about pathologic changes in Alzheimer's Disease (AD). METHOD AND MATERIALS Subjects were those newly enrolled in the ADNI2 study. Baseline data was used. T1 anatomical images were parcellated using FreeSurfer. DTI scans were registered to the T1 images using FSL. Structural connectomes were created using the Connectome Mapper Toolkit. Node degree, local efficiency, and clustering coefficient were calculated for the precuneus, posterior cingulate, inferior temporal, superior parietal, and superior frontal connectome nodes. The FreeSurfer parcellations were registered to the florbetapir PET scans. The global SUVR and four local SUVRs (frontal, cingulate, parietal, and temporal) were calculated. Clinical cognitive assessments included MMSE, ADAS-Cog, and Rey AVLT. Statistical analyses were performed between structural connection metrics, amyloid status, and clinical cognitive scores. RESULTS There were 102 ADNI2 subjects (64 males, 38 females) available at the time of the analysis. There were 37 normal control, 19 early mild cognitive impairment (MCI), 25 late MCI, and 21 AD subjects. All global and local AV45 amyloid burden measures were significantly associated with RAVLT, MMSE, and ADAS-Cog (p < 0.05). The strongest associations between amyloid burden and structural connection metrics were in the posterior cingulate and precuneus (node degree; p < 0.05). The strongest associations between structural connection metrics and clinical dementia scores were in the precuneus, superior parietal, and superior temporal regions (node degree vs. MMSE and ADAS-cog; p < 0.05). CONCLUSION Brain amyloid burden has significant associations with clinical cognitive status in all regions analyzed, consistent with globally increased amyloid burden as an important condition for AD. The strongest associations between amyloid burden and structural connection metrics were in the posterior cingulate and precuneus (node degree; p < 0.05), suggesting that these regions are most likely to have structural changes related to amyloid deposition in AD. CLINICAL RELEVANCE/APPLICATION The combination of quantitative amyloid PET and DTI tractography can provide information about global and local structural changes in AD, aiding in diagnosis and disease tracking.
    Radiological Society of North America 2013 Scientific Assembly and Annual Meeting; 12/2013
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Cerebral development involves a complex cascade of events which are difficult to visualize and quantify in vivo. In this study we combine information from Diffusion Tensor Imaging (DTI) and Quantitative Susceptibility Mapping (QSM) to analyze developing mouse brains at five stages up to 56days postnatal. Susceptibility maps were calculated using frequency shifts in gradient echo MR images acquired at 9.4T. Mean apparent magnetic susceptibility and magnetic susceptibility anisotropy of major white matter tracts were evaluated as a function of age. During the first two weeks, susceptibility of white matter appeared paramagnetic relative to surrounding gray matter; it then gradually became more diamagnetic. While diffusion anisotropy was already apparent and high at postnatal day 2, susceptibility anisotropy only became significant during the third week. This mismatch indicated different microstructural underpinnings for diffusion anisotropy and susceptibility anisotropy. Histological exams were also performed to evaluate myelin and iron content. It is confirmed that the main source of susceptibility contrast in WM is the myelin content. The ability to quantify the magnetic properties of white matter will provide valuable information on the architecture of the brain during development and potentially a more specific indicator for myelin degenerative diseases.
    NeuroImage 11/2013; · 6.13 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Disruption of the regulatory role of the kidneys leads to diverse renal pathologies; one major hallmark is inflammation and fibrosis. Conventional magnitude MRI has been used to study renal pathologies; however, the quantification or even detection of focal lesions caused by inflammation and fibrosis is challenging. We propose that quantitative susceptibility mapping (QSM) may be particularly sensitive for the identification of inflammation and fibrosis. In this study, we applied QSM in a mouse model deficient for angiotensin receptor type 1 (AT1 ). This model is known for graded pathologies, including focal interstitial fibrosis, cortical inflammation, glomerulocysts and inner medullary hypoplasia. We acquired high-resolution MRI on kidneys from AT1 -deficient mice that were perfusion fixed with contrast agent. Two MR sequences were used (three-dimensional spin echo and gradient echo) to produce three image contrasts: T1 , T2 * (magnitude) and QSM. T1 and T2 * (magnitude) images were acquired to segment major renal structures and to provide landmarks for the focal lesions of inflammation and fibrosis in the three-dimensional space. The volumes of major renal structures were measured to determine the relationship of the volumes to the degree of renal abnormalities and magnetic susceptibility values. Focal lesions were segmented from QSM images and were found to be closely associated with the major vessels. Susceptibilities were relatively more paramagnetic in wild-type mice: 1.46 ± 0.36 in the cortex, 2.14 ± 0.94 in the outer medulla and 2.10 ± 2.80 in the inner medulla (10(-2) ppm). Susceptibilities were more diamagnetic in knockout mice: -7.68 ± 4.22 in the cortex, -11.46 ± 2.13 in the outer medulla and -7.57 ± 5.58 in the inner medulla (10(-2) ppm). This result was consistent with the increase in diamagnetic content, e.g. proteins and lipids, associated with inflammation and fibrosis. Focal lesions were validated with conventional histology. QSM was very sensitive in detecting pathology caused by small focal inflammation and fibrosis. QSM offers a new MR contrast mechanism to study this common disease marker in the kidney. Copyright © 2013 John Wiley & Sons, Ltd.
    NMR in Biomedicine 10/2013; · 3.56 Impact Factor
  • Source
    Wei Li, Chunlei Liu
    [Show abstract] [Hide abstract]
    ABSTRACT: Susceptibility tensor imaging (STI) provides a novel approach for noninvasive assessment of the white matter pathways of the brain. Using mouse brain ex vivo, we compared STI with diffusion tensor imaging (DTI), in terms of tensor values, principal tensor values, anisotropy values, and tensor orientations. Despite the completely different biophysical underpinnings, magnetic susceptibility tensors and diffusion tensors show many similarities in the tensor and principal tensor images, for example, the tensors perpendicular to the fiber direction have the highest gray-white matter contrast, and the largest principal tensor is along the fiber direction. Comparing to DTI fractional anisotropy, the susceptibility anisotropy provides much higher sensitivity to the chemical composition of the white matter, especially myelin. The high sensitivity can be further enhanced with the perfusion of ProHance, a gadolinium-based contrast agent. Regarding the tensor orientations, the direction of the largest principal susceptibility tensor agrees with that of diffusion tensors in major white matter fiber bundles. The STI fiber tractography can reconstruct the fiber pathways for the whole corpus callosum and for white matter fiber bundles that are in close contact but in different orientations. There are some differences between susceptibility and diffusion tensor orientations, which are likely due to the limitations in the current STI reconstruction. With the development of more accurate reconstruction methods, STI holds the promise for probing the white matter micro-architectures with more anatomical details and higher chemical sensitivity.
    Journal of neuroscience and neuroengineering. 10/2013; 2(5):431-440.
  • [Show abstract] [Hide abstract]
    ABSTRACT: As indicated by several recent studies, magnetic susceptibility of the brain is influenced mainly by myelin in the white matter and by iron deposits in the deep nuclei. Myelination and iron deposition in the brain evolve both spatially and temporally. This evolution reflects an important characteristic of normal brain development and ageing. In this study, we assessed the changes of regional susceptibility in the human brain in vivo by examining the developmental and ageing process from 1 to 83 years of age. The evolution of magnetic susceptibility over this lifespan was found to display differential trajectories between the gray and the white matter. In both cortical and subcortical white matter, an initial decrease followed by a subsequent increase in magnetic susceptibility was observed, which could be fitted by a Poisson curve. In the gray matter, including the cortical gray matter and the iron-rich deep nuclei, magnetic susceptibility displayed a monotonic increase that can be described by an exponential growth. The rate of change varied according to functional and anatomical regions of the brain. For the brain nuclei, the age-related changes of susceptibility were in good agreement with the findings from R2(*) measurement. Our results suggest that magnetic susceptibility may provide valuable information regarding the spatial and temporal patterns of brain myelination and iron deposition during brain maturation and ageing. Hum Brain Mapp, 2013. © 2013 Wiley Periodicals, Inc.
    Human Brain Mapping 09/2013; 35(6). · 6.92 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: To propose a susceptibility map-weighted imaging (SMWI) method by combining a magnitude image with a quantitative susceptibility mapping (QSM) -based weighting factor thereby providing an alternative contrast compared with magnitude image, susceptibility-weighted imaging, and QSM. A three-dimensional multi-echo gradient echo sequence is used to obtain the data. The QSM was transformed to a susceptibility mask that varies in amplitude between zero and unity. This mask was multiplied several times with the original magnitude image to create alternative contrasts between tissues with different susceptibilities. A temporal domain denoising method to enhance the signal-to-noise ratio was further applied. Optimal reconstruction processes of the SMWI were determined from simulations. Temporal domain denoising enhanced the signal-to-noise ratio, especially at late echoes without spatial artifacts. From phantom simulations, the optimal number of multiplication and threshold values was chosen. Reconstructed SMWI created different contrasts based on its weighting factors made from paramagnetic or diamagnetic susceptibility tissue and provided an excellent delineation of microhemorrhage without blooming artifacts typically caused by the nonlocal property of phase. SMWI presents an alternative contrast for susceptibility-based imaging. The validity of this method was demonstrated using in vivo data. This proposed method together with denoising allows high-quality reconstruction of susceptibility-weighted image of human brain in vivo. Magn Reson Med, 2013. © 2013 Wiley Periodicals, Inc.
    Magnetic Resonance in Medicine 09/2013; · 3.40 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: PURPOSE: To present a novel technique for high-resolution stimulated echo diffusion tensor imaging with self-navigated interleaved spirals readout trajectories that can inherently and dynamically correct for image artifacts due to spatial and temporal variations in the static magnetic field (B0 ) resulting from eddy currents, tissue susceptibilities, subject/physiological motion, and hardware instabilities. METHODS: The Hahn spin echo formed by the first two 90° radiofrequency pulses is balanced to consecutively acquire two additional images with different echo times and generate an inherent field map, while the diffusion-prepared stimulated echo signal remains unaffected. For every diffusion-encoding direction, an intrinsically registered field map is estimated dynamically and used to effectively and inherently correct for off-resonance artifacts in the reconstruction of the corresponding diffusion-weighted image. RESULTS: After correction with the dynamically acquired field maps, local blurring artifacts are specifically removed from individual stimulated echo diffusion-weighted images and the estimated diffusion tensors have significantly improved spatial accuracy and larger fractional anisotropy. CONCLUSION: Combined with the self-navigated interleaved spirals acquisition scheme, our new method provides an integrated high-resolution short-echo time diffusion tensor imaging solution with inherent and dynamic correction for both motion-induced phase errors and off-resonance effects. Magn Reson Med, 2013. © 2013 Wiley Periodicals, Inc.
    Magnetic Resonance in Medicine 04/2013; · 3.40 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: PURPOSE: Approaches for quantitative mapping of electric conductivity and magnetic susceptibility using MRI have been developed independently. The purpose of this study is to present a method to simultaneously acquire information on conductivity and susceptibility and to produce images based on these properties. METHODS: A 3D multiecho gradient-echo sequence was used. Phase evolution during the multiecho was used to produce quantitative susceptibility maps, while the phase value at zero echo time was retrieved, and used to generates quantitative conductivity maps. Electromagnetic simulations were performed to evaluate the phase distribution due to conductivity variations. Phantom and in vivo data were also acquired to assess the quality of images produced. RESULTS: Simulations demonstrated that phase differences across objects increases with size and conductivity. For an accurate conductivity estimate, the maximum echo time was approximately equal to the true T2* value in order to achieve signal-to-noise ratio maximization. The most accurate susceptibility was obtained when separating phase contribution from conductivity. Phantom and in vivo results showed good quality images representing the electromagnetic properties. CONCLUSION: A simultaneous quantitative electromagnetic property imaging approach is demonstrated here. The approach not only improves the efficiency of mapping electromagnetic properties, but can also improve the accuracy of susceptibility mapping by separating image phases introduced by conductivity and susceptibility. Magn Reson Med, 2013. © 2013 Wiley Periodicals, Inc.
    Magnetic Resonance in Medicine 04/2013; · 3.40 Impact Factor
  • Source
    Chunlei Liu, Nicole E Murphy, Wei Li
    [Show abstract] [Hide abstract]
    ABSTRACT: Diffusion MRI has become an invaluable tool for studying white matter microstructure and brain connectivity. The emergence of quantitative susceptibility mapping and susceptibility tensor imaging (STI) has provided another unique tool for assessing the structure of white matter. In the highly ordered white matter structure, diffusion MRI measures hindered water mobility induced by various tissue and cell membranes, while susceptibility sensitizes to the molecular composition and axonal arrangement. Integrating these two methods may produce new insights into the complex physiology of white matter. In this study, we investigated the relationship between diffusion and magnetic susceptibility in the white matter. Experiments were conducted on phantoms and human brains in vivo. Diffusion properties were quantified with the diffusion tensor model and also with the higher order tensor model based on the cumulant expansion. Frequency shift and susceptibility tensor were measured with quantitative susceptibility mapping and susceptibility tensor imaging. These diffusion and susceptibility quantities were compared and correlated in regions of single fiber bundles and regions of multiple fiber orientations. Relationships were established with similarities and differences identified. It is believed that diffusion MRI and susceptibility MRI provide complementary information of the microstructure of white matter. Together, they allow a more complete assessment of healthy and diseased brains.
    Frontiers in Integrative Neuroscience 01/2013; 7:11.
  • [Show abstract] [Hide abstract]
    ABSTRACT: Altered brain connectivity has been widely considered as a genetic risk mechanism for schizophrenia. Of the many susceptibility genes identified so far, ZNF804A (rs1344706) is the first common genetic variant associated with schizophrenia on a genome-wide level. Previous fMRI studies have found that carriers of rs1344706 exhibit altered functional connectivity. However, the relationship between ZNF804A and white matter structural connectivity in patients of schizophrenia remains unknown. In this study, 100 patients with schizophrenia and 69 healthy controls were genotyped at the single nucleotide polymorphism rs1344706. Diffusion tensor imaging (DTI) was conducted and analyzed with tract-based spatial statistics. Systematic statistical analysis was conducted on multiple diffusion indices, including fractional anisotropy, axial diffusivity, radial diffusivity, and mean diffusivity. Unpaired two-sample t-test revealed significant differences in fractional anisotropy and diffusivity between schizophrenia and control groups. A two-way ANOVA analysis was conducted to assess the main effects of and the interaction between schizophrenia and ZNF804A. Although significant main effects of the diagnosis of schizophrenia were found on radial diffusivity, no association between the ZNF804A (rs1344706) and white matter connectivity was found in the entire group of subjects or in a selected subgroup of age-matched subjects (n=72).
    Neuroscience Letters 11/2012; · 2.06 Impact Factor
  • Chunlei Liu, Wei Li
    [Show abstract] [Hide abstract]
    ABSTRACT: Although magnetic fields interact weakly with biological tissues, at high fields, this interaction is sufficiently strong to cause measurable shifts in the Larmor frequency among various tissue types. (R2.1) While measuring frequency shift and its anisotropy has enabled NMR spectroscopy to determine structures of large molecules, MRI has not been able to fully utilize the vast information existing in the frequency to elucidate tissue microstructure. Using a multipole analysis of the complex MRI signal in the Fourier spectral space, we developed a fast and high-resolution method that enables the quantification of tissue's magnetic response with a set of magnetic susceptibility tensors of various ranks. The Fourier spectral space, termed p-space, can be generated by applying field gradients or equivalently by shifting the k-space data in various directions. (R2.2) Measuring these tensors allows the visualization and quantification of tissue architecture. We performed 3D whole-brain multipole susceptibility tensor imaging in simulation, on intact mouse brains ex vivo and on human brains in vivo. We showed that these multipole susceptibility tensors can be used to image orientations of ordered white matter fibers. These experiments demonstrate that multipole tensor analysis may enable practical mapping of tissue microstructure in vivo without rotating subject or magnetic field.
    NeuroImage 10/2012; · 6.13 Impact Factor

Publication Stats

936 Citations
177.34 Total Impact Points


  • 2013–2014
    • Duke University Medical Center
      • Brain Imaging and Analysis Center
      Durham, North Carolina, United States
  • 2009–2014
    • Duke University
      • Department of Medicine
      Durham, North Carolina, United States
  • 2004–2011
    • Stanford University
      • • Department of Electrical Engineering
      • • Department of Radiology
      Stanford, CA, United States
  • 2008–2009
    • Stanford Medicine
      • Department of Radiology
      Stanford, California, United States