• Investigative Magnetic Resonance Imaging
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• v.25 no.4
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• pp.252-265
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• 2021

Cardiac magnetic resonance imaging (MRI) serves as a clinical gold-standard non-invasive imaging technique for the assessment of global and regional cardiac function. Conventional cardiac MRI is limited by the long acquisition time, the need for ECG gating and/or long breathhold, and insufficient spatiotemporal resolution. Real-time cardiac cine MRI refers to high spatiotemporal cardiac imaging using data acquired continuously without synchronization or binning, and therefore of potential interest in overcoming the limitations of conventional cardiac MRI. Novel acquisition and reconstruction techniques must be employed to facilitate real-time cardiac MRI. The goal of this study is to discuss methods that have been developed for real-time cardiac MRI. In particular, we classified existing techniques into two categories based on the use of non-iterative and iterative reconstruction. In addition, we present several research trends in this direction, including deep learning-based image reconstruction and other advanced real-time cardiac MRI strategies that reconstruct images acquired from real-time free-breathing techniques.

• Progress in Medical Physics
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• v.25 no.2
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• pp.79-88
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• 2014

The dose distributions within the real volumes of tumor targets and critical organs during internal target volume-based intensity-modulated radiation therapy (ITV-IMRT) for liver cancer were recalculated by applying the effects of actual respiratory organ motion, and the dosimetric features were analyzed through comparison with gating IMRT (Gate-IMRT) plan results. The ITV was created using MIM software, and a moving phantom was used to simulate respiratory motion. The doses were recalculated with a 3 dose-volume histogram (3DVH) program based on the per-field data measured with a MapCHECK2 2-dimensional diode detector array. Although a sufficient prescription dose covered the PTV during ITV-IMRT delivery, the dose homogeneity in the PTV was inferior to that with the Gate-IMRT plan. We confirmed that there were higher doses to the organs-at-risk (OARs) with ITV-IMRT, as expected when using an enlarged field, but the increased dose to the spinal cord was not significant and the increased doses to the liver and kidney could be considered as minor when the reinforced constraints were applied during IMRT plan optimization. Because the Gate-IMRT method also has disadvantages such as unsuspected dosimetric variations when applying the gating system and an increased treatment time, it is better to perform a prior analysis of the patient's respiratory condition and the importance and fulfillment of the IMRT plan dose constraints in order to select an optimal IMRT method with which to correct the respiratory organ motional effect.

• The Journal of the Acoustical Society of Korea
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• v.39 no.1
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• pp.24-31
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• 2020

In this paper, the deep convolutional neural network for sound event detection is studied. Especially, the end-to-end neural network, which generates the detection results from the input audio waveform, is studied for weakly supervised problem that includes weakly-labeled and unlabeled dataset. The proposed system is based on the network structure that consists of deeply-stacked 1-dimensional convolutional neural networks, and enhanced by the skip connection and gating mechanism. Additionally, the proposed system is enhanced by the sound event detection and post processings, and the training step using the mean-teacher model is added to deal with the weakly supervised data. The proposed system was evaluated by the Detection and Classification of Acoustic Scenes and Events (DCASE) 2019 Task 4 dataset, and the result shows that the proposed system has F₁-scores of 54 % (segment-based) and 32 % (event-based).

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.10
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• pp.5149-5167
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• 2017

Reducing energy consumption in a wireless video sensor network (WVSN) is a crucial problem because of the high video data volume and severe energy constraints of battery-powered WVSN nodes. In this paper, we present an adaptive dynamic resizing approach for a SRAM communication buffer in a WVSN node in order to reduce the energy consumption and thereby, to maximize the lifetime of the WVSN nodes. To reduce the power consumption of the communication part, which is typically the most energy-consuming component in the WVSN nodes, the radio needs to remain turned off during the data buffer-filling period as well as idle period. As the radio ON/OFF transition incurs extra energy consumption, we need to reduce the ON/OFF transition frequency, which requires a large-sized buffer. However, a large-sized SRAM buffer results in more energy consumption because SRAM power consumption is proportional to the memory size. We can dynamically adjust any active buffer memory size by utilizing a power-gating technique to reflect the optimal control on the buffer size. This paper aims at finding the optimal buffer size, based on the trade-off between the respective energy consumption ratios of the communication buffer and the radio part, respectively. We derive a formula showing the relationship between control variables, including active buffer size and total energy consumption, to mathematically determine the optimal buffer size for any given conditions to minimize total energy consumption. Simulation results show that the overall energy reduction, using our approach, is up to 40.48% (26.96% on average) compared to the conventional wireless communication scheme. In addition, the lifetime of the WVSN node has been extended by 22.17% on average, compared to the existing approaches.

• Investigative Magnetic Resonance Imaging
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• v.19 no.1
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• pp.1-9
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• 2015

Purpose: Several morphometric studies have been performed to investigate brain abnormalities in congenitally deaf people. But no report exists concerning structural brain abnormalities in congenitally deaf adolescents. We evaluated the regional volume changes in gray matter (GM) using voxel-based morphometry (VBM) in congenitally deaf adolescents. Materials and Methods: A VBM8 methodology was applied to the T1-weighted magnetic resonance imaging (MRI) scans of eight congenitally deaf adolescents (mean age, 15.6 years) and nine adolescents with normal hearing. All MRI scans were normalized to a template and then segmented, modulated, and smoothed. Smoothed GM data were tested statistically using analysis of covariance (controlled for age, gender, and intracranial cavity volume). Results: The mean values of age, gender, total volumes of GM, and total intracranial volume did not differ between the two groups. In the auditory centers, the left anterior Heschl's gyrus and both inferior colliculi showed decreased regional GM volume in the congenitally deaf adolescents. The GM volumes of the lingual gyri, nuclei accumbens, and left posterior thalamic reticular nucleus in the midbrain were also decreased. Conclusions: The results of the present study suggest that early deprivation of auditory stimulation in congenitally deaf adolescents might have caused significant underdevelopment of the auditory cortex (left Heschl's gyrus), subcortical auditory structures (inferior colliculi), auditory gain controllers (nucleus accumbens and thalamic reticular nucleus), and multisensory integration areas (inferior colliculi and lingual gyri). These defects might be related to the absence of general auditory perception, the auditory gating system of thalamocortical transmission, and failure in the maturation of the auditory-to-limbic connection and the auditorysomatosensory-visual interconnection.

• JSTS:Journal of Semiconductor Technology and Science
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• v.16 no.6
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• pp.745-753
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• 2016

This paper presents a fully synthesizable low power interconnect bus for millimeter-scale wireless sensor nodes. A segmented ring bus topology minimizes the required chip real estate with low input/output pad count for ultra-small form factors. By avoiding the conventional open drain-based solution, the bus can be fully synthesizable. Low power is achieved by obviating a need for local oscillators in member nodes. Also, aggressive power gating allows low-power standby mode with only 53 gates powered on. An integrated wakeup scheme is compatible with a power management unit that has nW standby mode. A 3-module system including the bus is fabricated in a 180 nm process. The entire system consumes 8 nW in standby mode, and the bus achieves 17.5 pJ/bit/chip.

• Korean Journal of Remote Sensing
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• v.23 no.2
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• pp.145-152
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• 2007

The polarimetric backscattering coefficients of a wet-land rice field which is an experimental plot belong to National Institute of Agricultural Science and Technology in Suwon are measured using ground-based polarimetric scatterometers at 1.8 and 5.3 GHz throughout a growth year from transplanting period to harvest period (May to October in 2006). The polarimetric scatterometers consist of a vector network analyzer with time-gating function and polarimetric antenna set, and are well calibrated to get VV-, HV-, VH-, HH-polarized backscattering coefficients from the measurements, based on single target calibration technique using a trihedral corner reflector. The polarimetric backscattering coefficients are measured at $30^{\circ},\;40^{\circ},\;50^{\circ}\;and\;60^{\circ}$ with 30 independent samples for each incidence angle at each frequency. In the measurement periods the ground truth data including fresh and dry biomass, plant height, stem density, leaf area, specific leaf area, and moisture contents are also collected for each measurement. The temporal variations of the measured backscattering coefficients as well as the measured plant height, LAI (leaf area index) and biomass are analyzed. Then, the measured polarimetric backscattering coefficients are compared with the rice growth parameters. The measured plant height increases monotonically while the measured LAI increases only till the ripening period and decreases after the ripening period. The measured backscattering coefficientsare fitted with polynomial expressions as functions of growth age, plant LAI and plant height for each polarization, frequency, and incidence angle. As the incidence angle is bigger, correlations of L band signature to the rice growth was higher than that of C band signatures. It is found that the HH-polarized backscattering coefficients are more sensitive than the VV-polarized backscattering coefficients to growth age and other input parameters. It is necessary to divide the data according to the growth period which shows the qualitative changes of growth such as panicale initiation, flowering or heading to derive functions to estimate rice growth.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.5C
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• pp.355-364
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• 2012

Target processing mechanisms are necessary to collect target information, real-time data fusion, and tactical environment recognition for cooperative engagement ability. Among these mechanisms, the target tracking starts from predicting state of speed, acceleration, and location by using sensors' measurements. However, it can be a problem to give the reliability because the measurements have a certain uncertainty. Thus, a technique which uses multiple sensors is needed to detect the target and increase the reliability. Also, data fusion technique is necessary to process the data which is provided from heterogeneous sensors for target tracking. In this paper, a target tracking algorithm is proposed based on probabilistic data association(PDA) by fusing radar and ESM sensor measurements. The radar sensor's azimuth and range measurements and the ESM sensor's bearing-only measurement are associated by the measurement fusion method. After gating associated measurements, state estimation of the target is performed by PDA filter. The simulation results show that the proposed algorithm provides improved estimation under linear and circular target motions.

• The Korean Journal of Physiology
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• v.29 no.1
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• pp.13-27
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• 1995

single $K^{+}$ channels of skeletal muscle from the rat and frog were into planar lipid bilayers and their properties were studied. Fusion was induced by an osmotic gradient. Of the four types of $K^{+}$ channels recorded, the two most frequently observed were a voltage and $Ca^{2+}-activated$ $K^{+}$ channel and a $K^{+}$ channel with a prominent conductance substate. The first $K^{+}$ channel was identified as the large $Ca^{2+}-activated$ $K^{+}$ (BK) channel because the open-state probability was increased with depolarization (e-fold change per $10.6{\pm}3.5$ mV, n=8) and internal $Ca^{2+}$ (half-activation at $16.7{\pm}3.8$ mV, n=8, pCa 4) and its conductance was large ($247{\pm}4.9$ pS, n=24 in 0.1 M KCI). Lifetime distributions of open- and closed-states could be fitted with single exponentials of several milliseconds. The mean open- and closed-lifetimes were linearly dependent on the intracellular $[Ca^{2+}]$ and $1/[Ca^{2+}]$, respectively. The second $K^{+}$ channel showed a conductance substate at $30{\sim}60%$ of the open state. Its current-voltage relation was linear in the range of $-80\;{\sim}\;+80\;mV$. The slope conductance of the substate and open-state were 40 and 144 pS in 0.2 M KCl, respectively. The channel was highly selective for $K^{+}$ over Cl. The open-state probability was weakly voltage-dependent (e-fold change per 35 mV. The lifetime distributions of open- and closed-states were fitted with two exponentials and the major gating occurred slowly at several hundred milliseconds. Based on the above results, we think the second type of $K^{+}$ channel is the sarcoplasmic reticulum $K^{+}$ (SRK) channel. In addition, both types of channel were also incorporated into the lipids extracted from the skeletal muscle. The channel properties recorded in the bilayers termed from synthetic and extracted lipids were qualitatively similar. Our data indicate that BK and SRK channels are rich in the skeletal muscle and their properties and regulation could be effectively studied in planar lipid bilayer.

• Korean Journal of Radiology
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• v.23 no.2
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• pp.172-179
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• 2022

Objective: We aimed to evaluate the ostium of right coronary artery of anomalous origin from the left coronary sinus (AORL) with an interarterial course throughout the cardiac cycle on CT and analyze the clinical significance of the ostial findings. Materials and Methods: From January 2011 to December 2015, 68 patients (41 male, 57.3 ± 12.1 years) with AORL with an interarterial course and retrospective cardiac CT data were included. AORL was classified as high or low ostial location based on the pulmonary annulus in the diastolic and systolic phases on cardiac CT. In addition, the height, width, height/width ratio, area, and angle of the ostium were measured in both cardiac phases. After cardiac CT, patients were followed until December 31, 2020 for major adverse cardiac events (MACE). Clinical and CT characteristics associated with MACE were explored using Cox regression analysis. Results: During a median follow-up period of 2071 days (interquartile range, 1180.5-2747.3 days), 13 patients experienced MACE (19.1%, 13/68). Seven (10.3%, 7/68) had the ostial location change from high in the diastolic phase to low in the systolic phase. In the univariable analysis, younger age (hazard ratio [HR] = 0.918, p < 0.001), high ostial location (HR = 4.008, p = 0.036), larger height/width ratio (HR = 5.621, p = 0.049), and smaller ostial angle (HR = 0.846, p = 0.048) in the systolic phase were significant predictors of MACE. In multivariable cox regression analysis, younger age (adjusted HR = 0.917, p = 0.002) and high ostial location in the systolic phase (adjusted HR = 4.345, p = 0.026) were independent predictors of MACE. Conclusion: The ostial location of AORL with an interarterial course can change during the cardiac cycle, and high ostial location in the systolic phase was an independent predictor of MACE.