Je-Geun Chi

Gachon University, Seongnam, Gyeonggi, South Korea

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Publications (17)75.32 Total impact

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    ABSTRACT: The two basic scripts of the Korean writing system, Hanja (the logography of the traditional Korean character) and Hangul (the more newer Korean alphabet), have been used together since the 14th century. While Hanja character has its own morphemic base, Hangul being purely phonemic without morphemic base. These two, therefore, have substantially different outcomes as a language as well as different neural responses. Based on these linguistic differences between Hanja and Hangul, we have launched two studies; first was to find differences in cortical activation when it is stimulated by Hanja and Hangul reading to support the much discussed dual-route hypothesis of logographic and phonological routes in the brain by fMRI (Experiment 1). The second objective was to evaluate how Hanja and Hangul affect comprehension, therefore, recognition memory, specifically the effects of semantic transparency and morphemic clarity on memory consolidation and then related cortical activations, using functional magnetic resonance imaging (fMRI) (Experiment 2). The first fMRI experiment indicated relatively large areas of the brain are activated by Hanja reading compared to Hangul reading. The second experiment, the recognition memory study, revealed two findings, that is there is only a small difference in recognition memory for semantic transparency, while for the morphemic clarity was much larger between Hanja and Hangul. That is the morphemic clarity has significantly more effect than semantic transparency on recognition memory when studies by fMRI in correlation with behavioral study.
    Journal of Korean medical science. 10/2014; 29(10):1416-24.
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    ABSTRACT: Purpose To measure the activity of individual raphe nuclei with fluorine 18 fluorodeoxyglucose (FDG) and carbon 11 ((11)C) 3-amino-4-(2-dimethylaminomethylphenylthio) benzonitrile (DASB) imaging using a brain positron emission tomography(PET)/magnetic resonance (MR) imaging fusion system. Materials and Methods The study was approved by the Institutional Review Board of Gil Medical Center, and all volunteers provided written informed consent. FDG PET, (11)C-DASB PET, and T2*-weighted MR images from seven healthy volunteers were acquired by using a PET/MR imaging fusion system. The standard uptake value ratio (SUVR) of FDG (FDG-SUVR) and nondisplaceable binding potential (BPnd) of (11)C-DASB (DASB-BPnd) were determined for each raphe nucleus. A Pearson correlation analysis was performed to show the correlation between FDG-SUVR and DASB-BPnd for the raphe nuclei. Results Each raphe nucleus could be distinguished in both FDG (identifiability ratio, 0.86; κ = 0.77) and (11)C-DASB (identifiability ratio, 0.89; κ = 0.72) images. The mean values of DASB-BPnd for each raphe nucleus from dorsal to caudal direction were 6.08 (raphe nucleus 1), 5.93 (raphe nucleus 2), 3.86 (raphe nucleus 3), 3.18 (raphe nucleus 4), and 2.74 (raphe nucleus 5); the mean FDG-SUVR values were 1.00 (raphe nucleus 1), 1.00 (raphe nucleus 2), 0.87 (raphe nucleus 3), 0.94 (raphe nucleus 4), and 0.90 (raphe nucleus 5). FDG-SUVR and DASB-BPnd for the raphe nuclei were significantly correlated (r = 0.506, P = .002). Conclusion Serotonergic activity, both glucose metabolism and transporter binding potential of raphe nuclei, were measured with a brain-dedicated PET/MR imaging system and showed a significant correlation. © RSNA, 2014 Online supplemental material is available for this article.
    Radiology 03/2014; · 6.34 Impact Factor
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    ABSTRACT: Images obtained through ultra-high field 7.0T MRI with track-density imaging (TDI) provide clear and high resolution tractograms that have been hitherto unavailable, especially in deep brain areas such as the limbic and thalamic regions. Using this recently developed technique, we have identified four fiber tracts that have not previously been directly visualized in-vivo: the septum pellucidum tract (SPT), the anterior thalamic radiation (ATR), the superolateral medial forebrain bundle (slMFB), and the inferomedial forebrain bundle (imMFB). This is a largely pictorial description based on the new track density images we have obtained through 7.0T MRI with DWI-TDI. To identify the fiber tracts we selected three sets of tractograms and performed inter-axis correlation between them. These tractograms offer an opportunity for readers to extract new information, especially in the thalamo-limbic areas, which have previously been difficult to examine using either in-vivo or in-vitro human brain tractography. We present the high resolution images as a tool for researchers and clinicians working with neurodegenerative and psychiatric diseases such as Parkinson's Disease, Alzheimer's Disease, and depression, in which the accurate positioning of deep brain stimulation (DBS) is essential for precise targeting of nuclei and fiber tracts.
    World Neurosurgery 08/2013; · 1.77 Impact Factor
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    ABSTRACT: The anterior commissure (AC) and posterior commissure (PC) are the two distinct anatomic structures in the brain which are difficult to observe in detail with conventional MRI, such as a 1.5T MRI system. However, recent advances in ultra-high resolution MRI have enabled us to examine the AC and PC directly. The objective of the present study is to standardize the shape and size of the AC and PC using a 7.0T MRI and to propose a new brain reference line. Thirty-four, 21 males and 13 females, healthy volunteers were enrolled in this study. After determining the center of each AC and PC, we defined the connection of these centers as the central intercommissural line (CIL). We compared the known extra- and intra-cerebral reference lines with the CIL to determine the difference in the angles. Additionally, we obtained horizontal line from flat ground line of look front human. The difference in angle of the CIL and the tangential intercommissural line (TIL) from the horizontal line was 8.7 ± 5.1 (11 ± 4.8) and 17.4 ± 5.2 (19.8 ± 4.8) degrees in males and females, respectively. The difference in angle between the CIL and canthomeatal line was 10.1 in both male and female, and there was no difference between both sexes. Likewise, there was no significant difference in angle between the CIL and TIL between both sexes (8.3 +/- 1.1 in male and 8.8 +/- 0.7 in female). In this study, we have used 7.0T MRI to define the AC and PC quantitatively and in a more robust manner. We have showed that the CIL is a reproducible reference line and serves as a standard for the axial images of the human brain.
    Korean journal of radiology: official journal of the Korean Radiological Society 07/2013; 14(4):653-61. · 1.32 Impact Factor
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    ABSTRACT: The thalamus is one of the most important brain structures, with strong connections between subcortical and cortical areas of the brain. Most of the incoming information to the cortex passes through the thalamus. Accurate identification of substructures of the thalamus is therefore of great importance for the understanding of human brain connectivity. Direct visualization of thalamic substructures, however, is not easily achieved with currently available magnetic resonance imaging (MRI), including ultra-high field MRI such as 7.0T, mainly due to the limited contrast between the relevant structures. Recently, improvements in ultra-high field 7.0T MRI have opened the possibility of observing thalamic substructures by well-adjusted high-resolution T(1) -weighted imaging. Moreover, the recently developed super-resolution track-density imaging (TDI) technique, based on results from whole-brain fiber-tracking, produces images with sub-millimeter resolution. These two methods enable us to show markedly improved anatomical detail of the substructures of the thalamus, including their detailed locations and directionality. In this study, we demonstrate the role of TDI for the visualization of the substructures of the thalamic nuclei, and relate these images to T(1) -weighted imaging at 7.0T MRI. Hum Brain Mapp, 2012. © 2012 Wiley Periodicals, Inc.
    Human Brain Mapping 11/2012; · 6.88 Impact Factor
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    ABSTRACT: To investigate anatomical changes in the substantia nigra (SN) of Parkinson disease (PD) patients with age-matched controls by using ultra-high field magnetic resonance imaging (MRI). We performed 7T MRI in 10 PD and 10 age-matched control subjects. Magnetic resonance images of the SN were obtained from a 3-dimensional (3D) T(2)*-weighted gradient echo sequence. Region of interest-based 3D shape analysis was performed to quantitatively compare images from the 2 groups. The boundary between the SN and crus cerebri was not smooth in PD subjects. Undulation in the lateral surface of the SN appeared more intense in the side contralateral to that with the more severe symptoms, and more prominent at the rostral level of the SN than at the intermediate or caudal levels. In addition to the lateral surface, there was a striking difference in the dorsomedial aspects of the SN between PD and control subjects. In control subjects, a brighter signal region was observed along the dorsomedial surface of the lateral portion of SN, whereas in PD subjects, this region was observed as a dark region containing a hypointense signal in T(2)*-weighted images. The measurement of SN volumes, normalized to the intracranial volumes, showed higher values in PD subjects than in control subjects. This study demonstrates that 3D 7T MRI can definitively visualize anatomical alterations occurring in the SN of PD subjects. Further pathological studies are required to elucidate the nature of these anatomical alterations.
    Annals of Neurology 02/2012; 71(2):267-77. · 11.19 Impact Factor
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    ABSTRACT: The brainstem contains various important monoaminergic neuronal centers, including the raphe nuclei which contain serotonergic neurons. The raphe nuclei, however, are not easily identifiable and located by conventional neuroimaging. Fluorodeoxyglucose positron emission tomography (PET) and magnetic resonance imaging (MRI) were performed in seven healthy subjects using a new PET-MRI, which consists of a high-resolution research tomograph (HRRT) PET and 7.0 T-MRI. Glucose metabolism of raphe nuclei was semiquantitatively measured and identified along the midline brainstem region in vivo. Midline nuclei clustered in four groups appeared to be the raphe nuclei and could be clearly visualized; specifically, we identified the groups as the dorsal raphe, raphe reticularis centralis superior, raphe pontis, and raphe magnus group. FDG imaging of the midline raphe nuclei in vivo could potentially be an important tool for investigating brain diseases as well as conducting functional brain studies in the context of sleep disorders, depression, and neurodegenerative disease.
    NeuroImage 09/2011; 59(2):1094-7. · 6.25 Impact Factor
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    ABSTRACT: Parkinson's disease (PD) is a neurodegenerative disorder resulting from the progressive loss of dopaminergic (DA) neurons in the substantia nigra (SN). In our previous study, attempts were made to directly visualize the SN and quantify the differences in shapes and boundaries of the SN between PD subjects and comparison to the normal control subjects using two-dimensional T2*-weighted 7.0-T MRI images (Cho et al., Mov Disord, accepted for publication). However, a two-dimensional analysis does not represent the entire SN. Therefore, to overcome the limitation of 2D analysis, we acquire 3D image of the SN. For this study, we scanned nine PD patients, along with nine age-matched control subjects, using a research prototype 7.0-T MRI scanner in an attempt to visualize the 3D shape of the SN and quantify differences in the volume of the SN between PD subjects and normal control subjects. The shape change of the ventrolateral boundaries of the SN in PD cases was reconfirmed in this 3D study as well as in our previous 2D study (Cho et al., Mov Disord, accepted for publication). Another interesting finding of this study was that 3D MR imaging study demonstrated the potential of the 7.0-T MRI in the quantification of volume changes in the SN. The measured correlation analyses showed that there is age-dependent correlation and substantially stronger unified Parkinson's disease rating scale motor score-dependent correlation in PD patients. These results suggest that 7.0-T 3D T2*-weighted MR imaging could provide the quantitative estimation of volume changes in the SN in PD patients in vivo for comparison with normal controls in vivo. © 2011 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 21, 253–259, 2011;
    International Journal of Imaging Systems and Technology 08/2011; 21(3):253 - 259. · 0.64 Impact Factor
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    ABSTRACT: Parkinson's disease (PD) is a neurodegenerative disorder resulting from progressive loss of dopaminergic neurons in the substantia nigra (SN) pars compacta. Therefore, imaging of the SN has been regarded to hold greatest potential for use in the diagnosis of PD. At the 7.0T magnetic resonance imaging (MRI), it is now possible to delineate clearly the shapes and boundaries of the SN. We scanned eight early and two advanced PD patients, along with nine age-matched control subjects, using a 7.0T MRI in an attempt to directly visualize the SN and quantify the differences in shape and boundaries of SN between PD subjects in comparison with the normal control subjects. In the normal controls, the boundaries between the SN and crus cerebri appear smooth, and clean "arch" shapes that stretch ventrally from posterior to anterior. In contrast, these smooth and clean arch-like boundaries were lost in PD subjects. The measured correlation analyses show that, in PD patients, there is age-dependent correlation and substantially stronger UPDRS motor score-dependent correlation. These results suggest that, by using 7.0T MRI, it appears possible to use these visible and distinctive changes in morphology as a diagnostic marker of PD.
    Movement Disorders 03/2011; 26(4):713-8. · 5.63 Impact Factor
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    ABSTRACT: The anatomy of the thalamus and its connectivity with surrounding areas are known. Localized metabolic activities at the thalamic substructural level have not been measured in vivo in human brains because of limited resolution and contrast. The energy metabolism and fine anatomic structures of the thalamus were measured simultaneously in 5 healthy subjects using a PET/MRI fusion imaging system. Measured metabolism in individual thalamic nuclei was quantified by corresponding PET/MRI images. Substructures of the thalamus were clearly distinguished in 7.0-T MRI images, and the corresponding metabolic activities measured by PET were integrated by the PET/MRI system. The medial dorsal thalamic nucleus consistently showed the highest glucose uptake among the thalamic nuclei. These results demonstrate that substructure-specific metabolic activities in the thalamus can be measured with a PET/MRI system consisting of an ultra-high-resolution PET component and an ultra-high-field MRI component.
    Journal of Nuclear Medicine 02/2011; 52(3):401-4. · 5.77 Impact Factor
  • Journal of Nuclear Medicine 01/2011; · 5.77 Impact Factor
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    ABSTRACT: Authors had prepared the high-quality sectioned images of a cadaver head. For the delineation of each cerebral gyrus, three-dimensional model of the same brain was required. The purpose of this study was to develop the segmentation protocol of cerebral gyri by referring to the three-dimensional model on the personal computer. From the 114 sectioned images (intervals, 1 mm), a cerebral hemisphere was outlined. On MRIcro software, sectioned images including only the cerebral hemisphere were volume reconstructed. The volume model was rotated to capture the lateral, medial, superior, and inferior views of the cerebral hemisphere. On these four views, areas of 33 cerebral gyri were painted with colors. Derived from the painted views, the cerebral gyri in sectioned images were identified and outlined on the Photoshop to prepare segmented images. The segmented images were used for production of volume and surface models of the selected gyri. The segmentation method developed in this research is expected to be applied to other types of images, such as MRIs. Our results of the sectioned and segmented images of the cadaver brain, acquired in the present study, are hopefully utilized for medical learning tools of neuroanatomy.
    Journal of Korean medical science 12/2010; 25(12):1710-5. · 0.84 Impact Factor
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    ABSTRACT: The hippocampus is one of the best-known neural structures in the brain and has been of interest in observing the substructures and their metabolic functions. However, it has been difficult to distinguish its substructures and functions in vivo because of its small size. (18)F-FDG PET and high-resolution MRI of the hippocampus were performed on 5 healthy subjects using a PET/MRI system. The metabolism of each hippocampal substructure was measured in vivo on the basis of the MR images. The dentate gyrus and cornu ammonis 4 showed the highest glucose uptake in the healthy subjects. Measuring glucose metabolism in the substructures of the hippocampus could provide a new tool for the future investigation of related brain diseases or functional studies, such as Alzheimer disease or memory and learning studies.
    Journal of Nuclear Medicine 10/2010; 51(10):1545-8. · 5.77 Impact Factor
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    ABSTRACT: Sectional anatomy of human brain is useful to examine the diseased brain as well as normal brain. However, intracerebral reference points for the axial, sagittal, and coronal planes of brain have not been standardized in anatomical sections or radiological images. We made 2,343 serially-sectioned images of a cadaver head with 0.1 mm intervals, 0.1 mm pixel size, and 48 bit color and obtained axial, sagittal, and coronal images based on the proposed reference system. This reference system consists of one principal reference point and two ancillary reference points. The two ancillary reference points are the anterior commissure and the posterior commissure. And the principal reference point is the midpoint of two ancillary reference points. It resides in the center of whole brain. From the principal reference point, Cartesian coordinate of x, y, z could be made to be the standard axial, sagittal, and coronal planes.
    Journal of Korean medical science 01/2010; 25(1):135-41. · 0.84 Impact Factor
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    ABSTRACT: A challenge associated with deep brain stimulation (DBS) in treating advanced Parkinson disease (PD) is the direct visualization of brain nuclei, which often involves indirect approximations of stereotactic targets. In the present study, the authors compared T2*-weighted images obtained using 7-T MR imaging with those obtained using 1.5- and 3-T MR imaging to ascertain whether 7-T imaging enables better visualization of targets for DBS in PD. The authors compared 1.5-, 3-, and 7-T MR images obtained in 11 healthy volunteers and 1 patient with PD. With 7-T imaging, distinct images of the brain were obtained, including the subthalamic nucleus (STN) and internal globus pallidus (GPi). Compared with the 1.5- and 3-T MR images of the STN and GPi, the 7-T MR images showed marked improvements in spatial resolution, tissue contrast, and signal-to-noise ratio. Data in this study reveal the superiority of 7-T MR imaging for visualizing structures targeted for DBS in the management of PD. This finding suggests that by enabling the direct visualization of neural structures of interest, 7-T MR imaging could be a valuable aid in neurosurgical procedures.
    Journal of Neurosurgery 01/2010; 113(3):639-647. · 3.15 Impact Factor
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    ABSTRACT: Unlike computed tomographic images and magnetic resonance images (MRIs), sectioned images of the human body with real color and high resolution have certain advantages in learning and teaching anatomy. Comparisons between sectioned images of the brain and MRIs are useful in many ways. Therefore, we prepared 312 MRIs at ultrahigh field 7.0 T (axial direction 0.4 times 0.4 times 0.4 mm<sup>3</sup> voxel size) of a cadaver brain, 2343 sectioned images (axial direction, 0.1 mm intervals, 0.1 times 0.1 mm<sup>2</sup> pixel size, and 48 bits color) by serial-sectioning the cadaver head, 234 segmented images in which brain regions were separately delineated (1 mm intervals and 0.1 times 0.1 mm<sup>2</sup> pixel size) by outlining 64 head structures in sectioned images. Three-dimensional images of 64 head structures were made by volume reconstruction from sectioned images. In this research, advanced techniques and equipment enabled us to prepare quality 7.0-T MRIs, sectioned images, and segmented images of the head. These images are expected to contribute to our understanding of the topographic neuroanatomy of the head and to aid interpretations of MRIs and CTs of the human brain.
    Proceedings of the IEEE 01/2010; · 6.91 Impact Factor
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    ABSTRACT: In-vivo volumetric measurements of hippocampus have proven to be highly informative for studying various neurological diseases such as Alzheimer's disease. The usefulness of volumetric imaging, however, has been limited due to the poor image resolutions obtained by currently available MRI images. In this study, a new result of volumetric image measurement of the hippocampus using 7.0 T MRI images of high contrast and resolution is described. To verify the usefulness of the proposed method, its reliability and sensitivity were examined and compared with existing imaging techniques such as 1.5 T or 3.0 T MRI imaging. The results of our study with 7.0 T MRI clearly demonstrated superior boundary detection for the hippocampal head, body, and tail compared with low field MRIs. In conclusion, robust and reproducible volumetric measurements as well as 3D images of clear contrast obtained with 7.0 T suggest the usefulness of high field MR imaging and its eventual use for the accurate diagnosis of hippocampal diseases and related research.
    NeuroImage 11/2009; 49(3):2134-40. · 6.25 Impact Factor

Publication Stats

155 Citations
75.32 Total Impact Points

Institutions

  • 2009–2013
    • Gachon University
      • Neuroscience Research Institute
      Seongnam, Gyeonggi, South Korea
  • 2012
    • Austin Health
      Melbourne, Victoria, Australia
  • 2011
    • Seoul National University
      • Department of Pathology
      Seoul, Seoul, South Korea
  • 2010
    • Dongguk University
      • Department of Anatomy
      Seoul, Seoul, South Korea