• Journal of Biomedical Engineering Research
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• v.27 no.2
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• pp.64-72
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• 2006

The present study introduces a new cortical patch-based source model for EEG/MEG cortical source imaging to consider anatomical constraints more precisely. Conventional source models for EEG/MEG cortical source imaging have used coarse cortical surface mesh or sampled small number of vertices from fine surface mesh, and thus they failed to utilize full anatomical information which nowadays we can get with sub-millimeter modeling accuracy. Conventional ones placed a single dipolar source on each cortical patch and estimated its intensity by means of various inverse algorithms; whereas the suggested cortical patch-based model integrates whole cortical area to construct lead field matrix and estimates current density that is assumed to be constant in each cortical patch. We applied the proposed and conventional models to realistic EEG data and compared the results quantitatively. The quantitative comparisons showed that the proposed model can provide more precise spatial descriptions of neuronal source distribution.

• Journal of Biomedical Engineering Research
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• v.42 no.6
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• pp.295-303
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• 2021

Idiopathic normal-pressure hydrocephalus (INPH) is considered a potentially treatable neurological disorder by shunt surgery and characterized by a triad of symptoms including gait disturbance, cognitive impairment and urinary dysfunction. Although disorders of white matter are generally viewed as the principal pathological features of INPH, analysis of cortical features are important since the destruction of neural tracts could be associated with cortical structural changing. The aim of the study was to determine whether there was any relationship between gait parameter and structural features of cerebral cortex in INPH patients. Gait parameters were measured as follows: step width, toe in/out angle, coefficient of variation (CV) value of stride length, CV value of stride time. After obtaining individual brain MRI of patients with INPH and hemispheric cortical surfaces were automatically extracted from each MR volume, which reconstructed the inner and outer cortical surface. Then, cortical thickness, surface area, and volume were calculated from the cortical surface. As a result, step width was positively correlated with bilateral postcentral gyrus and left precentral gyrus, and toe in/out was positively correlated with left posterior parietal cortex and left insula. Also, the CV value of stride length showed positive correlation in the right superior frontal sulcus, left insula, and the CV value of stride time showed positive correlation in the right superior frontal sulcus. Unique parameter of cerebral cortical changes, as measured using MRI, might underline impairments in distinct gait parameters in patients with INPH.

• Journal of Biomedical Engineering Research
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• v.28 no.4
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• pp.549-555
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• 2007

In order to study cortical properties in human, it is necessary to obtain an accurate and explicit representation of the cortical surface in individual subjects. Among many approaches, surface-based method that reconstructs a 3-D model from contour lines on cross-section images is widely used. In general, however, medical brain imaging has some problems such as the complexity of the images, non-linear gain artifacts and so on. Due these limitations, therefore, extracting anatomical structures from imaging data is very a complicated and time-consuming task. In this paper, we present an improved method for extracting contour lines of cortical surface from magnetic resonance images that simplifies procedures of a conventional method. The conventional method obtains contour lines through thinning and chain code process. On the other hand, the proposed method can extract contour lines from comparison between boundary data and labeling image without supplementary processes. The usefulness of the proposed method has been verified using brain image.

• Investigative Magnetic Resonance Imaging
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• v.19 no.3
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• pp.168-177
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• 2015

Purpose: Brain surface intensity model (BSIM)-based cortical thickness analysis does not require complicated 3D segmentation of brain gray/white matters. Instead, this technique uses the local intensity profile to compute cortical thickness. The aim of the present study was to evaluate intra-rater and inter-rater reliability of BSIM-based cortical thickness analysis using images from elderly participants. Materials and Methods: Fifteen healthy elderly participants (ages, 55-84 years) were included in this study. High-resolution 3D T1-spoiled gradient recalled-echo (SPGR) images were obtained using 3T MRI. BSIM-based processing steps included an inhomogeneity correction, intensity normalization, skull stripping, atlas registration, extraction of intensity profiles, and calculation of cortical thickness. Processing steps were automatic, with the exception of semiautomatic skull stripping. Individual cortical thicknesses were compared to a database indicating mean cortical thickness of healthy adults, in order to produce Z-score thinning maps. Intra-class correlation coefficients (ICCs) were calculated in order to evaluate inter-rater and intra-rater reliabilities. Results: ICCs for intra-rater reliability were excellent, ranging from 0.751-0.940 in brain regions except the right occipital, left anterior cingulate, and left and right cerebellum (ICCs = 0.65-0.741). Although ICCs for inter-rater reliability were fair to excellent in most regions, poor inter-rater correlations were observed for the cingulate and occipital regions. Processing time, including manual skull stripping, was $17.07{\pm}3.43min$. Z-score maps for all participants indicated that cortical thicknesses were not significantly different from those in the comparison databases of healthy adults. Conclusion: BSIM-based cortical thickness measurements provide acceptable intra-rater and inter-rater reliability. We therefore suggest BSIM-based cortical thickness analysis as an adjunct clinical tool to detect cortical atrophy.

• Development and Reproduction
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• v.2 no.2
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• pp.157-163
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• 1998

Preimplantation embryos of the rat was examined by the morphological changes in the cortical granule envelope (CGE), blastomere surface, and zona pellucida (ZP) of embryo after cortical reaction. The ultrastructural characteristics and CGE of embryos were observed with the scanning electron microscope and fluorescence microscope. In the ultrastructural characteristic of embryo surface, surface microvilli were shortened and the CGE-like structure existed above microvilli in eight-cell embryo. Rough spongy surface and decreased network numbers were key characters of embryonic ZP compared to unfertilized oocyte. The CGE formed by cortical reaction existed in perivitelline space during embryo development but it was thin and locally distributed ill contrast to fertilized oocyte. The present results indicate that cortical reaction forms cortical granule envelope in perivitelline space and causes not only zona hardening, but also ultrastructural changes in ZP and cell membrane of preimplantation embryos.

• Restorative Dentistry and Endodontics
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• v.43 no.3
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• pp.33.1-33.8
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• 2018

Objectives: This study aimed to investigate the prevalence of a separate distolingual root and to measure the thickness of the buccal cortical bone in mandibular first molars in Koreans using cone-beam computed tomography (CBCT) images. Materials and Methods: High-quality CBCT data from 432 patients were analyzed in this study. The prevalence of a separate distolingual root of the mandibular first molar was investigated. The distance from the distobuccal and distolingual root apices to the outer surface of the buccal cortical bone was measured. We also evaluated the thickness of the buccal cortical bone. Results: The prevalence of a separate distolingual root (2 separate distal roots with 1 canal in each root; 2R2C) was 23.26%. In mandibular first molars with 2R2C, the distance from the distobuccal root apex to the outer surface of the buccal cortical bone was 5.51 mm. Furthermore, the distance from the distolingual root apex to the outer surface of the buccal cortical bone was 12.09 mm. In mandibular first molars with 2R2C morphology, the thickness of the buccal cortical bone at the distobuccal root apex of the mandibular first molar was 3.30 mm. The buccal cortical bone at the distobuccal root apex was significantly thicker in the right side (3.38 mm) than the left side (3.09 mm) (p < 0.05). Conclusions: A separate distolingual root is not rare in mandibular first molars in the Korean population. Anatomic and morphologic knowledge of the mandibular first molar can be useful in treatment planning, including surgical endodontic treatment.

• Journal of Biomedical Engineering Research
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• v.44 no.1
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• pp.53-63
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• 2023

There have been many studies from the genetic system to physical activity and emotional expression such that there are gender differences. The purpose of this study was to determine how the structural characteristics of cortical thickness differ between males and females. This study used data from the Human Connectome Project (HCP). To analyze age-specific sexual dimorphisms of cortical thickness, selected 8-80 year old subjects were divided into five detailed age range groups according to each criterion. A total of 1,700 individual brain MRI T1 data were registered in stereotaxic space for analysis and classified into white matter (WM), gray matter (GM), and cerebro-spinal fluid (CSF). For surface-based analysis, the WM/GM surface was reconstructed from a spherical polygon model with 40962 vertices per hemisphere, and each vertex was extended to the GM/CSF boundary. Cortical thickness was then measured between each vertex using the t-link method. In the statistical analysis, intracranial volume was used as a covariate to exclude the effect of the difference in brain size of each individual, and the result of using age as a covariate was added to confirm the age effect within each group. Gender differences in cortical thickness had significant results by group. This may be an index to explain diseases with sexual dimorphism in prevalence or become a basis for explaining the characteristics of each sex that appear in behavior, personality, and aging. Therefore, the results of our study could be a criterion for age classification in future studies and for understanding 'normal' sexual dimorphism.

• Korean Journal of Radiology
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• v.22 no.5
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• pp.782-791
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• 2021

Objective: To evaluate the signal intensity of the periosteum using ultrashort echo time pulse sequence with three-dimensional cone trajectory (3D UTE) with or without fat suppression (FS) to distinguish from artifacts in porcine tibias. Materials and Methods: The periosteum and overlying soft tissue of three porcine lower legs were partially peeled away from the tibial cortex. Another porcine tibia was prepared as three segments: with an intact periosteum outer and inner layer, with an intact periosteum inner layer, and without periosteum. Axial T1 weighted sequence (T1 WI) and 3D UTE (FS) were performed. Another porcine tibia without periosteum was prepared and subjected to 3D UTE (FS) and T1 WI twice, with positional changes. Two radiologists analyzed images to reach a consensus. Results: The three periosteal tissues that were partially peeled away from the cortex showed a high signal in 3D UTE (FS) and low signal on T1 WI. 3D UTE (FS) showed a high signal around the cortical surface with an intact outer and inner periosteum, and subtle high signals, mainly around the upper cortical surfaces with the inner layer of the periosteum and without periosteum. T1 WI showed no signal around the cortical surfaces, regardless of the periosteum state. The porcine tibia without periosteum showed changes in the high signal area around the cortical surface as the position changed in 3D UTE (FS). No signal was detected around the cortical surface in T1 WI, regardless of the position change. Conclusion: The periosteum showed a high signal in 3D UTE and 3D UTE FS that overlapped with artifacts around the cortical bone.

• Journal of Dental Rehabilitation and Applied Science
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• v.23 no.1
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• pp.55-68
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• 2007

The purpose of this study was to analyze the distribution of stress in the surrounding bone around implant placed in the first and second molar region. Two different three-dimensional finite element model were designed according to vertical bone level around fixture ($4.0mm{\times}11.5mm$) on the second molar region. A mandibular segment containing two implant-abutments and a two-unit bridge system was molded as a cancellous core surrounded by a 2mm cortical layer. The mesial and distal section planes of the model were not covered by cortical bone and were constrained in all directions at the nodes. Two vertical loads and oblique loads of 200 N were applied at the center of occlusal surface (load A) or at a position of 2mm apart buccally from the center (load B). Von-Mises stresses were analyzed in the supporting bone. The results were as follows; 1. With the vertical load at the center of occlusal surface, the stress pattern on the cortical and cancellous bones around the implant on model 1 and 2 was changed, while the stress pattern on the cancellous bone with oblique load was not. 2. With the vertical load at the center of occlusal surface, the maximum von-Mises stress appeared in the outer distal side of the cortical bone on Model 1 and 2, while the maximum von-Mises stress appeared in the distal and lingual distal side of the cortical bone with oblique load. 3. With the vertical load at a position of 2 mm apart buccally from the center, there was the distribution of stress on the upper portion of the implant-bone interface and the cortical bone except for the cancellous bone, while there was a distribution of stress on the cancellous bones at the apical and lingual sides around the fixture and on the cortical bone with oblique load. 4. With the changes of the supporting bone on the second molar area, the stress pattern on the upper part of the cortical bone between two implants was changed, while the stress pattern on the cancellous bone was not. The results of this study suggest that establishing the optimum occlusal contact considering the direction and position of the load from the standpoint of stress distribution of surrounding bone will be clinically useful.

• Journal of Biomedical Engineering Research
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• v.39 no.6
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• pp.237-242
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• 2018

$^{18}F$-fludeoxyglucose PET (FDG-PET) can help finding an abnormal metabolic activity in brain. In this study, we evaluated an efficiency of volume- and cortical surface-based analysis which were used to determine whether standardized uptake value ratio (SUVR) of FDG-PET was different among Alzheimer's disease (AD), mild cognitive impairment (MCI), and healthy control (HC). Each PET image was rigidly co-registered to the corresponding magnetic resonance imaging (MRI) using mutual information. All voxels of the co-registered PET images were divided by the mean FDG uptake of the cerebellum cortex which was thresholded by partial volume effect (>0.9). Also, the SUVR value of each vertex was linearly interpolated from volumetric SUVR image which was thresholded by gray matter partial volume effect (>0.1). Lobar mean values were calculated from both volume- and cortical surface-based SUVRs. Statistical analysis was conducted to compare two measures for AD, MCI and HC groups. Even though the results of volume (SUVR_vol) and cortical surface-based SUVR (SUVR_surf) analysis were not significantly different from each other, the latter would be better for detecting group differences in SUVR of PET.