k-Space Deep Learning for Reference-free EPI Ghost Correction

Nyquist ghost artifacts in EPI are originated from phase mismatch between the even and odd echoes. However, conventional correction methods using reference scans often produce erroneous results especially in high-field MRI due to the non-linear and time-varying local magnetic field changes. Recently, it was shown that the problem of ghost correction can be reformulated as k-space interpolation problem that can be solved using structured low-rank Hankel matrix approaches. Another recent work showed that data driven Hankel matrix decomposition can be reformulated to exhibit similar structures as deep convolutional neural network. By synergistically combining these findings, we propose a k-space deep learning approach that immediately corrects the phase mismatch without a reference scan in both accelerated and non-accelerated EPI acquisitions. To take advantage of the even and odd-phase directional redundancy, the k-space data is divided into two channels configured with even and odd phase encodings. The redundancies between coils are also exploited by stacking the multi-coil k-space data into additional input channels. Then, our k-space ghost correction network is trained to learn the interpolation kernel to estimate the missing virtual k-space data. For the accelerated EPI data, the same neural network is trained to directly estimate the interpolation kernels for missing k-space data from both ghost and subsampling. Reconstruction results using 3T and 7T in-vivo data showed that the proposed method outperformed the image quality compared to the existing methods, and the computing time is much faster.The proposed k-space deep learning for EPI ghost correction is highly robust and fast, and can be combined with acceleration, so that it can be used as a promising correction tool for high-field MRI without changing the current acquisition protocol.Comment: To appear in Magnetic Resonance in Medicin

Improving Noise Robustness in Subspace-based Joint Sparse Recovery

In a multiple measurement vector problem (MMV), where multiple signals share a common sparse support and are sampled by a common sensing matrix, we can expect joint sparsity to enable a further reduction in the number of required measurements. While a diversity gain from joint sparsity had been demonstrated earlier in the case of a convex relaxation method using an $l_1/l_2$ mixed norm penalty, only recently was it shown that similar diversity gain can be achieved by greedy algorithms if we combine greedy steps with a MUSIC-like subspace criterion. However, the main limitation of these hybrid algorithms is that they often require a large number of snapshots or a high signal-to-noise ratio (SNR) for an accurate subspace as well as partial support estimation. One of the main contributions of this work is to show that the noise robustness of these algorithms can be significantly improved by allowing sequential subspace estimation and support filtering, even when the number of snapshots is insufficient. Numerical simulations show that a novel sequential compressive MUSIC (sequential CS-MUSIC) that combines the sequential subspace estimation and support filtering steps significantly outperforms the existing greedy algorithms and is quite comparable with computationally expensive state-of-art algorithms

Mesenchymal Stem Cells Improve Wound Healing In Vivo via Early Activation of Matrix Metalloproteinase-9 and Vascular Endothelial Growth Factor

We investigated the effects of mesenchymal stem cells (MSCs) on wound healing using a three-dimensional (3D) collagen gel scaffold. Three circular full-thickness skin defects were created on the back of Sprague-Dawley rats. One site was covered with a 3D collagen gel containing 2 × 106 MSCs (MSCs+/3D collagen+). Another site was replaced with a 3D collagen gel without MSCs and the third site was left empty. The wound size was significantly reduced in the MSCs+/3D collagen+ sites. MSCs+/3D collagen+ sites exhibited the most neovascularization. FISH showed that Y-chromosome possessing cells were found within the dermis of MSCs+/3D collagen+ sites. Gelatin zymography revealed that the most intense expression of MMP-9 was detected early in the MSCs+/3D collagen+ sites. Our results indicate that MSCs upregulate the early expression of MMP-9 which induces the early mobilization of VEGF. Thus, MSCs appear to accelerate significantly wound healing via early activation of MMP-9 and VEGF

Cyber Black Box: Network intrusion forensics system for collecting and preserving evidence of attack

Once the system is compromised, the forensics and investigation are always executed after the attacks and the loss of some useful instant evidence. Since there is no log information necessary for analyzing an attack cause after the cyber incident occurs, it is difficult to analyze the cause of an intrusion even after an intrusion event is recognized. Moreover, in an advanced cyber incident such as advanced persistent threats, several months or more are expended in only analyzing a cause, and it is difficult to find the cause with conventional security equipment. In this paper, we introduce a network intrusion forensics system for collecting and preserving the evidence of an intrusion, it is called Cyber Black Box that is deployed in Local Area Network environment. It quickly analyzes a cause of an intrusion event when the intrusion event occurs, and provides a function of collecting evidence data of the intrusion event. The paper also describes the experimental results of the network throughput performance by deploying our proposed system in an experimental testbed environment

Assessment of Agricultural Drought Considering the Hydrological Cycle and Crop Phenology in the Korean Peninsula

Hydrological changes attributable to global warming increase the severity and frequency of droughts, which in turn affect agriculture. Hence, we proposed the Standardized Agricultural Drought Index (SADI), which is a new drought index specialized for agriculture and crops, and evaluated current and expected droughts in the Korean Peninsula. The SADI applies crop phenology to the hydrological cycle, which is a basic element that assesses drought. The SADI of rice and maize was calculated using representative hydrological variables (precipitation, evapotranspiration, and runoff) of the crop growing season. In order to evaluate the effectiveness of SADI, the three-month Standardized Precipitation Index, which is a representative drought index, and rainfed crop yield were estimated together. The performance evaluation of SADI showed that the correlation between rainfed crop yield and SADI was very high compared with that of existing drought index. The results of the assessment of drought over the past three decades provided a good indication of a major drought period and differentiated the results for crops and regions. The results of two future scenarios showed common drought risks in the western plains of North Korea. Successfully validated SADIs could be effectively applied to agricultural drought assessments in light of future climate change, and would be a good example of the water-food nexus approach

Assessment of Agricultural Drought Considering the Hydrological Cycle and Crop Phenology in the Korean Peninsula

Hydrological changes attributable to global warming increase the severity and frequency of droughts, which in turn affect agriculture. Hence, we proposed the Standardized Agricultural Drought Index (SADI), which is a new drought index specialized for agriculture and crops, and evaluated current and expected droughts in the Korean Peninsula. The SADI applies crop phenology to the hydrological cycle, which is a basic element that assesses drought. The SADI of rice and maize was calculated using representative hydrological variables (precipitation, evapotranspiration, and runoff) of the crop growing season. In order to evaluate the effectiveness of SADI, the three-month Standardized Precipitation Index, which is a representative drought index, and rainfed crop yield were estimated together. The performance evaluation of SADI showed that the correlation between rainfed crop yield and SADI was very high compared with that of existing drought index. The results of the assessment of drought over the past three decades provided a good indication of a major drought period and differentiated the results for crops and regions. The results of two future scenarios showed common drought risks in the western plains of North Korea. Successfully validated SADIs could be effectively applied to agricultural drought assessments in light of future climate change, and would be a good example of the water-food nexus approach

A Study on Development of Optimal Noise Filter Algorithm for Laser Vision System in GMA Welding

AbstractIn recent years, noise filter of image processing have been widely used in automated manufacturing processes in noisy environment, such as removal of noise in arc welding process, because such filters are robust even in the presence of extreme noise. Since arc, soot and splash etc., salt noise which has certain noise amplitude at random location was found in captured image. It is important to employ a noise filter to intensify the laser lines and ultimately remove or reduce the noise. In this study, the welding seam image captured from the CCD camera was processed by noise filters to remove the noise due to the complexity of welding environment. Comparison of three noise filters (Gaussian filter, Median filter and Wiener filter) was made to find out the optimal noise filtering algorithm. The result showed that the Median filter algorithm is the preferred method, as not only this algorithm performance provided lower MSE (Mean Square Error) and RMSE (Root Mean Square Error) values than those of Gaussian filter and Wiener filter, but also the values of the PSNR (Peak Signal-to-Noise Ratio) and SNR (Signal-to-Noise Ratio) were higher. Therefore, the Median filter can be considered to have a better enhancement effect than the other two filters

Estimation of HIV Seroprevalence in Colorectal Hospitals by Questionnaire Survey in Korea, 2002–2007

AbstractObjectivesThe incidence of anal disease is higher among persons with human immunodeficiency virus (HIV) infection than among the general population. We surveyed the status of seroprevalence in colorectal hospitals in Korea.MethodsThe survey was conducted in colorectal hospitals in Korea from November to December 2008. The questionnaire was comprised of six topics about the status of HIV testing in colorectal hospitals. We gathered the data by website (http://hivqa.nih.go.kr/risk) or fax.ResultsAmong 774 colorectal hospitals contacted, 109 (14%) hospitals participated in the survey. Among these, 48 hospitals (44%) performed HIV tests in their own hospitals and 11 (23%) took HIV testing by rapid method. The main reason for recommending an HIV test was surgical operation (54%) followed by endoscope (11%) and health checkup (9%). The annual number of HIV tests increased from 58,647 (at 21 hospitals) in 2002 to 246,709 (at 58 hospitals) in 2007. HIV seroprevalence was >3.0 per 10,000 individuals during 2002–2005, decreased to 2.2 per 10,000 individuals in 2006 and rose to 2.8 per 10,000 individuals in 2007.ConclusionsHIV seroprevalence of colorectal hospitals was more than twice that of general hospitals in Korea. HIV surveillance systems based on colorectal hospitals for HIV/AIDS transmission prevention by early HIV diagnosis are needed