Biomedical subjects

Dae-Jin Kim

Publications and source records attributed to Dae-Jin Kim.

4 recordsLinked to original sources

PubMed2006

How does distortion correction correlate with anisotropic indices? A diffusion tensor imaging study.

PURPOSE: The purpose of this study was to determine a suitable registration algorithm for diffusion tensor imaging (DTI) using conventional preprocessing tools [statistical parametric mapping (SPM) and automated image registration (AIR)] and to investigate how anisotropic indices for clinical assessments are affected by these distortion corrections. MATERIALS AND METHODS: Brain DTI data from 15 normal healthy volunteers were used to evaluate four spatial registration schemes within subjects to correct image distortions: noncorrection, SPM-based affine registration, AIR-based affine registration and AIR-based nonlinear polynomial warping. The performance of each distortion correction was assessed using: (a) quantitative parameters: tensor-fitting error (Ef), mean dispersion index (MDI), mean fractional anisotropy (MFA) and mean variance (MV) within 11 regions of interest (ROI) defined from homogeneous fiber bundles; and (b) fiber tractography through the uncinate fasciculus and the corpus callosum. Fractional anisotropy (FA) and mean diffusivity (MD) were calculated to demonstrate the effects of distortion correction. Repeated-measures analysis of variance was used to investigate differences among the four registration paradigms. RESULTS: AIR-based nonlinear registration showed the best performance for reducing image distortions with respect to smaller Ef (P<.02), MDI (P<.01) and MV (P<.01) with larger MFA (P<.01). FA was decreased to correct distortions (P<.0001) whether the applied registration was linear or nonlinear and was lowest after nonlinear correction (P<.001). No significant differences were found in MD. CONCLUSION: In conventional DTI processing, anisotropic indices of FA can be misestimated by noncorrection or inappropriate distortion correction, which leads to an erroneous increase in FA. AIR-based nonlinear distortion correction would be required for a more accurate measurement of this diffusion parameter.

Adult↗

PubMed2005

Formation of a protein monomolecular layer by a combined technique of LB and SA methods.

This paper describes a technique developed for the formation of the self-assembled protein monomolecular layer. The main idea is a direct transfer of protein molecules consisting of a Langmuir-Blodgett (LB) film onto the surface of another chemically modified metal substrate and induction of the spontaneous formation of a self-assembled monolayer (SAM) by chemisorption without protein aggregates. In the present experiments, a cytochrome c (cyt c) SAM on a gold substrate was prepared by incubating a EDC/MUA-modified gold substrate overlaid with a cyt c LB film in a phosphate buffer solution. Scanning tunneling microscopy (STM) image of a cyt c SAM shows that the size of cyt c clusters in the most part of the substrate is approximately 5 nm, indicating the cyt c monomolecular layer. The rectifying property of a cyt c monolayer was confirmed to remain by an asymmetric I-V curve in the applied bias from -1 V to 1 V.

Animals↗

PubMed2004

Nonlinear-analysis of human sleep EEG using detrended fluctuation analysis.

Quantification of the fractal scaling properties of human sleep EEG dynamics was sought and each normal sleep stage was compared with that of sleep apnea. The fractal scaling exponents that quantify power-law correlations were computed using detrended fluctuation analysis. Six healthy subjects, aged 30-35 years, participated and six recordings of the apnea were acquired from MIT/BIH polysomnography database. The data were 8-h baseline recordings (23:00-07:00 h). The EEG signals from the C4-A1 derivation were acquired with a resolution of 250 Hz. The sleep stages were visually scored for 30 s epochs, according to the criteria of Rechtschaffen and Kales. The mean scaling exponents increased from the awake stage to stages 1, 2 and 3-4, but decreased during rapid eye movement (REM) sleep. The scaling exponents of the apnea were lower than those of the healthy subject for all the stages. The scaling exponents could be attributed to the fractal nature of EEG, which would be more appropriate for describing the complexity of EEG due to its assumption of non-stationarity.

Adult↗

PubMed2004

Th1, Th2 and Th3 cytokine alteration in schizophrenia.

BACKGROUND: Several studies have shown that there is an imbalance between T helper 1 (Th1) cytokines and T helper 2 (Th2) cytokines in patients with schizophrenia. The T helper 3 (Th3) cytokine, transforming growth factor beta-1 (TGF-beta1), has been shown to suppress the production of Th1 cytokines. Therefore it is hypothesized that it may play a role in schizophrenia by suppressing overactive Th1 system. METHODS: We recruited 88 schizophrenic patients and 88 matched controls. The basal plasma concentrations of IFN-gamma (Th1), IL-4 (Th2) and TGF-beta1 (Th3) were studied at the time the patients were admitted to the hospital and following 8 weeks of treatment with antipsychotics. RESULTS: The detection rate of plasma IFN-gamma and basal plasma TGF-beta1 level were significantly higher in schizophrenic patients than in controls whereas detection rate of plasma IL-4 was lower in patients. The ratio of Th1/Th2 cytokines (IFN-gamma/IL-4) was higher in schizophrenic patients. Following the neuroleptic treatment, the IFNgamma and TGF-beta1 levels returned to control values, and IL-4 concentration rose above the control value. CONCLUSION: Schizophrenic patients showed higher Th1/Th2 ratio which is attenuated by effective neuroleptic treatment. It is possible that TGF-beta1 plays a role in reducing the activity of Th1 cytokine.

Adolescent↗