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광대역 원형편파 스피드론 프랙탈 유전체 공진기 시퀀셜 로테이션 배열 안테나
황동휘(Hwang Dong Hyee),임홍준(Lim Hong Jun),황금철(Hwang Keum Cheol) 한국통신학회 2021 한국통신학회 학술대회논문집 Vol.2021 No.2
본 논문은 새로운 형상의 광대역 원형편파 스피드론 프랙탈 유전체 공진기 시퀀셜 로테이션 배열 안테나를 제안한다. 원형편파 특성을 갖는 단일 스피드론 프랙탈 유전체 공진기 안테나와 시퀀셜 로테이션 급전 네트워크를 각각 설계하고 결합하여 광대역 원형편파 스피드론 프랙탈 유전체 공진기 시퀀셜 로테이션 배열 안테나를 설계 및 제작하였다. 제안된 안테나의 3 dB 축비 대역폭은 29.18%(2.02-2.71 GHz)로 넓은 대역폭 특성을 갖고 있고, 3 dB 축비 대역폭 내에서 최대 이득은 12.66 dBic 로 고이득 특성을 보였다.
이시영,강승관,황동휘,이재성 대한핵의학회 2020 핵의학 분자영상 Vol.54 No.6
Purpose Early deep-learning-based image denoising techniques mainly focused on a fully supervised model that learns how to generate a clean image from the noisy input (noise2clean: N2C). The aim of this study is to explore the feasibility of the selfsupervised methods (noise2noise: N2N and noiser2noise: Nr2N) for PET image denoising based on the measured PET data sets by comparing their performance with the conventional N2C model. Methods For training and evaluating the networks, 18F-FDG brain PET/CT scan data of 14 patients was retrospectively used (10 for training and 4 for testing). From the 60-min list-mode data, we generated a total of 100 data bins with 10-s duration. We also generated 40-s-long data by adding four non-overlapping 10-s bins and 300-s-long reference data by adding all list-mode data. We employed U-Net that is widely used for various tasks in biomedical imaging to train and test proposed denoising models. Results All the N2C, N2N, and Nr2N were effective for improving the noisy inputs. While N2N showed equivalent PSNR to the N2C in all the noise levels, Nr2N yielded higher SSIM than N2N. N2N yielded denoised images similar to reference image with Gaussian filtering regardless of input noise level. Image contrast was better in the N2N results. Conclusion The self-supervised denoising method will be useful for reducing the PET scan time or radiation dose.
Arun Gupta,김경윤,황동휘,이민선,이동수,이재성 한국물리학회 2018 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.72 No.11
SPECT plays important role in peptide receptor targeted radionuclide therapy using theranostic radionuclides such as Lu-177 for the treatment of various cancers. However, SPECT studies must be quantitatively accurate because the reliable assessment of tumor uptake and tumor-to-normal tissue ratios can only be performed using quantitatively accurate images. Hence, it is important to evaluate performance parameters and quantitative accuracy of preclinical SPECT systems for therapeutic radioisotopes before conducting pre- and post-therapy SPECT imaging or dosimetry studies. In this study, we evaluated system performance and quantitative accuracy of NanoSPECT/CT scanner for Lu-177 imaging using point source and uniform phantom studies. We measured recovery coefficient, uniformity, spatial resolution, system sensitivity and calibration factor for mouse whole body standard aperture. We also performed the experiments using Tc-99m to compare the results with that of Lu-177. We found that the recovery coefficient of more than 70% for Lu-177 at the optimum noise level when nine iterations were used. The spatial resolutions of Lu-177 with and without adding uniform background was comparable to that of Tc-99m in axial, radial and tangential directions. System sensitivity measured for Lu-177 was almost three times less than that of Tc-99m.
황완균,박형순,함인혜,오미현,남궁홍,김현기,황동휘,허수영,김태영,박용규,김재룡,김진우 생화학분자생물학회 2005 Experimental and molecular medicine Vol.37 No.5
Coumarins comprise a group of natural phenolic compounds found in a variety of plant sources. In view of the established low toxicity, relative cheapness, presence in the diet and occurrence in various herbal remedies of coumarins, it appears prudent to evaluate their properties and applications further. The purpose of this study is to investigate celular protective activity of coumarin compound, fraxin extracted from Weigela florida var. glabbra, under oxidative stress, to identify genes expressed differentially by fraxin and to compare antioxidative effect of fraxin with its struc-the coumarins, protective effects of fraxin against cytotoxicity induced by H2O2 were examined in human umbilical vein endothelial cells (HUVECs). Fraxin showed free radical scavenging effect at high concentration (0.5 mM) and cell protective effect against H2O2-mediated oxidative stress. Fraxin recovered viability of HUVECs damaged by H2O2- treatment and reduced the lipid peroxidation and the internal reactive oxygen species level elevated by H2O2 treatment. Differential display reverse transcrip-tion-PCR revealed that fraxin upregulated antiapo-ptotic genes (clusterin and apoptosis inhibitor 5) and tumor suppressor gene (ST13). Based on structural similarity comparing with fraxin, seven chemicals, fraxidin methyl ether (29.4% enhancement of viability), prenyletin (26.4%), methoxsalen (20.8 %), diffratic acid (19.9%), rutoside (19.1%), xanthyletin (18.4%), and kuhlmannin (18.2%), enhanced more potent cell via-bility in the order in comparison with fraxin, which showed only 9.3% enhancement of cell viability. These results suggest that fraxin and fraxin-related che-micals protect HUVECs from oxidative stress.