Hyung-Wook Choi

Diagnostic Yield of Double-Dose Gadobutrol in the Detection of Brain Metastasis: Intraindividual Comparison with Double-Dose Gadopentetate Dimeglumine

BACKGROUND AND PURPOSE: Accurate assessment of the number and lesion characteristics of brain metastasis is very important in GKS. The purpose of this study was to compare the diagnostic efficacy of DD gadobutrol in the detection of brain metastases compared with a DD 0.5-mol/L gadolinium contrast, gadopentetate dimeglumine. MATERIALS AND METHODS: Records of 27 patients (male to female ratio, 15:12; mean age, 57.1 years) diagnosed with brain metastasis and having undergone GKS were retrospectively analyzed. All patients underwent the first 3D-T1-GRE MR imaging with a DD of gadopentetate dimeglumine. The second MR imaging with a DD of gadobutrol was performed during GKS by using the same parameters used for the first scan. Two neuroradiologists counted the number of enhancing lesions on 2 consecutive MR imaging examinations and reached consensus. Lesion-brain CNR was measured from 45 lesions, and paired t test analysis was performed between DD gadopentetate dimeglumine and gadobutrol MR imaging. RESULTS: On DD gadopentetate dimeglumine−enhanced images, a total of 130 lesions were detected visually. With DD gadobutrol, 25 additional lesions were detected on GKS MR imaging. There was no missing lesion on DD gadobutrol MR imaging. The mean lesion-brain CNR was higher on DD gadobutrol MR imaging than on DD gadopentetate dimeglumine imaging (2.17 ± 0.19 versus 1.90 ± 0.26; P = .00011, paired t test, 2-tailed). Only 2 cases showed lower CNR on DD gadobutrol images: 1 with hemorrhagic metastasis from renal cell carcinoma and the other with steroid treatment after the first MR imaging. CONCLUSIONS: DD 1.0-mol/L gadobutrol provides higher lesion conspicuity and enhances lesion detection in brain metastasis compared with DD 0.5-mol/L gadolinium contrast agents.

Electrical and optical properties of PLZT thin films on ITO coated glass by sol-gel processing

Sol-gel processed PLZT thin films were fabricated on ITO-coated glass substrates with RTA (rapid thermal annealing). The electrical and optical properties such as hysteresis curves, dielectric constant, dielectric loss and optical transmittance of thin films were investigated. The PLZT thin films were crystallized to the perovskite structure by RTA at 750°C for 5 min. As the La percentage was increased, the dielectric constant increased, and that of 9/65/35 PLZT thin film was 1750. The coercive field and remnant polarization decreased with La increase from 33.82 kV/cm to 14.71 kV/cm and from 39.26 μC/cm2 to 9.57 μC/cm2 respectively. As the Zr percentage increased at 2% La, the coercive field decreased from 52.94 kV/cm to 30 kV/cm, but the remnant polarization increased from 22.74 μC/cm2 to 50.75 μC/cm2, and the dielectric constant had a maximum value of 1269 at 2/55/45 composition. The optical transmittance was increased as La percentage increased but was decreased as the annealing temperature increased.

Photoluminescence Characteristics of Nanocrystalline ZnGa2O4 Phosphors Obtained at Different Sintering Temperatures

A nano-sized ZnGa2O4 phosphor was synthesized via a precipitation method (at a low temperature) and then sintered at various temperatures. X-ray diffraction (XRD) analysis confirmed that single-crystalline ZnGa2O4 particles were formed. A pure ZnGa2O4 phase was obtained at a sintering temperature of 1000°C. Theaverage size of the spherical ZnGa2O4-phosphor particles increased with increasing sintering temperature. The most intense photoluminescence (PL) peak – corresponding to blue emission at about 420 nm – was observed for the sample prepared at a sintering temperature of 1000°C.

Photoluminescence Characteristics of Y3Al5O12:Ce3+ Phosphors Synthesized Using the Combustion Method with Various Reagents

Ce-doped yttrium aluminum garnet (YAG; Y3Al5O12) phosphor powders were synthesized using the combustion method. The luminescence, formation process, and structure of the phosphor powders were investigated by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), and photoluminescence (PL) spectroscopy. The XRD patterns show that the YAG phase can be produced with this method by sintering at 1000 °C for 2 h. This temperature is much lower than that required to synthesize the YAG phase using the conventional solid-state reaction method. No intermediate phases such as yttrium aluminum perovskite (YAP; YAlO3) or yttrium aluminum monoclinic (YAM; Y4Al2O9) were observed as a result of the sintering process. The powders were found to absorb excitation energies in the range of 410–510 nm. Furthermore, the crystalline YAG:Ce powder phosphor produced broad emission peaks in the range of 480–600 nm with the maximum intensity at 528 nm.

Changes in Integrity of Normal-Appearing White Matter in Patients with Moyamoya Disease: A Diffusion Tensor Imaging Study

BACKGROUND AND PURPOSE: DTI is widely used for the evaluation of white matter integrity in various neurologic diseases. The purpose of this study was to investigate changes in white matter integrity by using DTI in NAWM of patients with MMD and to evaluate the correlation between diffusion and perfusion characteristics through an interhemispheric comparison. MATERIALS AND METHODS: We retrospectively reviewed 20 primary MMD patients with asymmetric disease stage and 20 age-matched healthy controls. FACS and ADCCS values of bilateral centrum semiovale were measured by using region of interest analysis. Mean FACS and ADCCS were compared between patient and control groups by unpaired t test. Interhemispheric differences in FACS and ADCCS were assessed and compared between the H-TTPdelayed and the H-TTPshorter by using paired t test. AIs also were assessed to verify interhemispheric differences. RESULTS: The patient group showed a significantly lower mean FACS and a higher mean ADCCS value than the control group. In the patient group, the H-TTPdelayed had a significantly lower FACS and higher ADCCS value than the H-TTPshorter. Both AIFA and AIADC were significantly higher in the patient compared with the control group. CONCLUSIONS: DTI can describe subtle changes in white matter integrity in NAWM of patients with primary MMD that are not detected by conventional MR imaging. In addition, diffusion characteristics are well correlated with perfusion characteristics. We believe that DTI is a useful ancillary tool to evaluate patients with MMD.

Hydrogenated Amorphous Silicon Layer Formation by Inductively Coupled Plasma Chemical Vapor Deposition and Its Application for Surface Passivation of p-Type Crystalline Silicon

The satisfactory surface passivation properties of hydrogenated amorphous silicon (a-Si:H) prepared by inductively coupled plasma chemical vapor deposition (ICP-CVD) at a low temperature (400 °C) on p-type crystalline silicon wafers are reported. Certain parameters, such as SiH4/H2 ratio, annealing temperature, film thickness, and substrate temperature, were varied to determine their optimal levels. Completely amorphous layers with a broad transverse optic (TO) mode peak at approximately 480 cm-1 were identified by Raman spectroscopy, and an optical band gap of approximately 1.6 eV was determined from optical absorption data. A maximum carrier lifetime of 53 µs for an a-Si:H thickness of 15 nm and an annealing temperature of 450 °C was measured for 525-µm-thick p-type crystalline silicon (c-Si) substrates with a resistivity in the range of 1–20 Ω cm by the quasi-steady-state photoconductance (QSSPC) method. The lowest value of interface trapped charge density (Dit) of approximately 3.34 ×1011 cm-2 eV-1 was estimated by capacitance–voltage (C–V) measurement using a metal–insulator–semiconductor (MIS) structure. Furthermore, simple processing with satisfactory results can be achieved with substrate heating at 400 °C during deposition. The optimal conditions of a SiH4/H2 gas ratio of 1/1 and a substrate temperature of 400 °C were implemented for a passivation layer thickness of 5 nm.

Synthesis of Nanocrystalline ZnGa2O4 Phosphor with Different Concentrations via a Precipitation Method

In this study, nanocrystalline zinc gallate (ZnGa2O4) phosphors were prepared by a precipitation method using aqueous ammonia as the precipitant. This method enabled the low temperature formation of phosphors with spherical shape. The samples were characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM), and cathodoluminescence (CL). The highest diffraction intensity was observed for the sample with a metal ion concentration of 0.1 mol/dm3. The sample with this metal ion concentration had nanocrystalline ZnGa2O4 phosphor with an average size of about 80 nm. The emission spectra of ZnGa2O4 showed a broad self-activated blue emission band spanning over in the wide range of 300–600 nm with a peak wavelength of about 420 nm; this band showed a maximum intensity at a metal ion concentration of 0.1 mol/dm3.

Luminescence Characteristics of ZnGa 2 O 4 :Mn 2+ ,Cr 3+ Phosphor and Thick Film

In this study, phosphors in its application to field emission displays and electroluminescence were synthesized through the precipitation method and ions. A green luminescence activator, ions, and a red luminescence activator were separately doped into , which was then screen printed to an indium tin oxide substrate. The thick films of the were deposited with the various thicknesses using nano-sized powder. The best luminescence characteristics were shown at a thickness of 60 . Additionally, green-emission and red-emission phosphor thick films, which have superior characteristics, were manufactured through the screen-printing method. These results indicate that phosphors prepared through the precipitation method have wide application as phosphor of the full color emission.

Fabrication of YSZ/GDC Bilayer Electrolyte Thin Film for Solid Oxide Fuel Cells

Copyright ©2014 KIEEME. All rights reserved. This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted noncommercial use, distribution, and reproduction in any medium, provided the original work is properly cited. pISSN: 1229-7607 eISSN: 2092-7592 DOI: http://dx.doi.org/10.4313/TEEM.2014.15.4.189 TRANSACTIONS ON ELECTRICAL AND ELECTRONIC MATERIALS Vol. 15, No. 4, pp. 189-192, August 25, 2014

Electrical properties of Pb(Zr0.52 Ti0.48)O3 thin films prepared by SOL-GEL processing

Abstract Thin films of Pb(Zr0.52 Ti0.48)O3 were prepared on Pt/SiO2/Si substrates by sol-gel processing and rapid thermal annealing (RTA). The variations of hysteresis curves of the films with different upper electrode materials were studied. In order to investigate the effects of electrode - film interface on the electrical characteristics of the PZT film, the leakage current of the film was observed. While the PZT films with silver electrodes deposited at the substrate temperature of 150°C showed ferroelectric characteristics, the films with silver electrodes deposited at room temperature showed the decreased remanent polarization and the asymmetric hysteresis curves. The films thicker than 0.5 μm with platinum electrodes exhibited fine squareness on the hysteresis curves. However, 0.28 μm thick PZT films with silver electrodes and with platinum electrodes have the coercive fields of 39 kV/cm and 68 kV/cm, the remanent polarization of 21 μC/cm2 and 20 μC/cm2, and the switching voltages of Vp = 6 V and V...