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Data‐driven synthetic MRI FLAIR artifact correction via deep neural network
Ryu, Kanghyun,Nam, Yoonho,Gho, Sung‐,Min,Jang, Jinhee,Lee, Ho‐,Joon,Cha, Jihoon,Baek, Hye Jin,Park, Jiyong,Kim, Dong‐,Hyun RADIOLOGICAL SOCIETY OF NORTH AMERICA INC 2019 Journal of Magnetic Resonance Imaging Vol. No.
<P><B>Background</B></P><P>FLAIR (fluid attenuated inversion recovery) imaging via synthetic MRI methods leads to artifacts in the brain, which can cause diagnostic limitations. The main sources of the artifacts are attributed to the partial volume effect and flow, which are difficult to correct by analytical modeling. In this study, a deep learning (DL)‐based synthetic FLAIR method was developed, which does not require analytical modeling of the signal.</P><P><B>Purpose</B></P><P>To correct artifacts in synthetic FLAIR using a DL method.</P><P><B>Study Type</B></P><P>Retrospective.</P><P><B>Subjects</B></P><P>A total of 80 subjects with clinical indications (60.6 ± 16.7 years, 38 males, 42 females) were divided into three groups: a training set (56 subjects, 62.1 ± 14.8 years, 25 males, 31 females), a validation set (1 subject, 62 years, male), and the testing set (23 subjects, 57.3 ± 20.4 years, 13 males, 10 females).</P><P><B>Field Strength/Sequence</B></P><P>3 T MRI using a multiple‐dynamic multiple‐echo acquisition (MDME) sequence for synthetic MRI and a conventional FLAIR sequence.</P><P><B>Assessment</B></P><P>Normalized root mean square (NRMSE) and structural similarity (SSIM) were computed for uncorrected synthetic FLAIR and DL‐corrected FLAIR. In addition, three neuroradiologists scored the three FLAIR datasets blindly, evaluating image quality and artifacts for sulci/periventricular and intraventricular/cistern space regions.</P><P><B>Statistical Tests</B></P><P>Pairwise Student's <I>t</I>‐tests and a Wilcoxon test were performed.</P><P><B>Results</B></P><P>For quantitative assessment, NRMSE improved from 4.2% to 2.9% (<I>P</I> < 0.0001) and SSIM improved from 0.85 to 0.93 (<I>P</I> < 0.0001). Additionally, NRMSE values significantly improved from 1.58% to 1.26% (<I>P</I> < 0.001), 3.1% to 1.5% (<I>P</I> < 0.0001), and 2.7% to 1.4% (<I>P</I> < 0.0001) in white matter, gray matter, and cerebral spinal fluid (CSF) regions, respectively, when using DL‐corrected FLAIR. For qualitative assessment, DL correction achieved improved overall quality, fewer artifacts in sulci and periventricular regions, and in intraventricular and cistern space regions.</P><P><B>Data Conclusion</B></P><P>The DL approach provides a promising method to correct artifacts in synthetic FLAIR.</P><P><B>Level of Evidence</B>: 4</P><P><B>Technical Efficacy</B>: Stage 1</P><P>J. Magn. Reson. Imaging 2019;50:1413–1423.</P>
Ryoo, Kanghyun,Hwang, Sang-Gil,Kim, Kwang Je,Choi, Eui-Ju Dr. W. Junk B. V. Publishers ; Kluwer Academic Pub 2015 MOLECULAR AND CELLULAR BIOCHEMISTRY - Vol.402 No.1
<P>RC3/neurogranin is a postsynaptic protein and plays pivotal roles in spatial learning and emotional anxiety as well as synaptic plasticity. The expression level of RC3 is dynamically changed during developmental stages, but the function of RC3 in brain development is not well understood yet. Neurotrophins interact with tropomyosin-related kinase receptors to activate Ras-extracellular signal-regulated kinase (ERK) pathway and can also induce neuronal differentiation. In this study, we demonstrate that RC3 inhibits Ras-ERK pathway by interaction with Ras and controls neurite outgrowth induced by neurotrophins. In PC12 cells, RC3 inhibits nerve growth factor (NGF)-induced activation of Ras and thereby ERK1/2 signaling cascade as well as neurite outgrowth induced by NGF. We found Ras is the target of the inhibitory function of RC3, because RC3 interacts with Ras and suppresses the elevated affinity of Ras to Ras-binding domain of Raf-1. Meanwhile, already activated Raf-1 by Ras activity is not affected by RC3. Furthermore, depletion of RC3 by RNA interference drastically enhances the stimulation of ERK1/2 and neurite outgrowth induced by brain-derived neurotrophic factor in hippocampal neurons. These findings suggest that RC3 is a novel natural inhibitor of Ras-ERK1/2 signaling axis, leading to negatively regulate neuronal differentiation induced by neurotrophins.</P>
Enhancement of the anisotropic photocurrent in ferroelectric oxides by strain gradients
Chu, Kanghyun,Jang, Byung-Kweon,Sung, Ji Ho,Shin, Yoon Ah,Lee, Eui-Sup,Song, Kyung,Lee, Jin Hong,Woo, Chang-Su,Kim, Seung Jin,Choi, Si-Young,Koo, Tae Yeong,Kim, Yong-Hyun,Oh, Sang-Ho,Jo, Moon-Ho,Yang, Nature Publishing Group 2015 Nature nanotechnology Vol.10 No.11
The phase separation of multiple competing structural/ferroelectric phases has attracted particular attention owing to its excellent electromechanical properties. Little is known, however, about the strain-gradient-induced electronic phenomena at the interface of competing structural phases. Here, we investigate the polymorphic phase interface of bismuth ferrites using spatially resolved photocurrent measurements, present the observation of a large enhancement of the anisotropic interfacial photocurrent by two orders of magnitude, and discuss the possible mechanism on the basis of the flexoelectric effect. Nanoscale characterizations of the photosensitive area through position-sensitive angle-resolved piezoresponse force microscopy and electron holography techniques, in conjunction with phase field simulation, reveal that regularly ordered dipole-charged domain walls emerge. These findings offer practical implications for complex oxide optoelectronics.
브레이크 마찰력 증가를 위한 상용차용 전기-기계식 브레이크의 쐐기 설계
이상민(Sang Min Lee),박정훈(Jeonghun Park),남강현(Kanghyun Nam),유창희(Chang-Hee Yoo),박상신(Sang-Shin Park) 한국트라이볼로지학회 2018 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.34 No.2
This paper proposes a new type of electro-mechanical wedge brake for commercial vehicles. The brake operates on a novel mechanism for self-boosting braking friction forces using eccentric shafts, and involves wedges that are inserted between the rampbridge and traverse; this self-boosting mechanism is explained herein. A dynamic analysis using ADAMS was conducted, and the findings are reported. The constraint and contact conditions are explained to verify the precision of the dynamic analysis. The dynamic analysis shows that in the proposed mechanism, the self-boosting effect occurs as desired. However, it is also noted that the system has a limitation in terms of the production of unlimited braking forces that can jam the roller inside the wedges. After demonstrating the self-boosting effect, dynamic analyses are performed for several values of the wedge angles and friction coefficients between the brake pads and disks. Conventionally, a lower wedge angle has been suggested owing to its provision of a larger clamping force for given friction coefficients. However, it is noted that lower wedge angles can lead to a higher probability of occurrence of undesirable high braking forces, which can jam the roller into the wedge; thus, a larger wedge angle is preferable for avoiding the undesirable jamming phenomena. These analysis results are presented and discussed herein.