• Journal of the Korean Society of Radiology
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• v.82 no.2
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• pp.406-416
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• 2021

Purpose To evaluate the association between magnetic resonance imaging (MRI)-based texture parameters and Kirsten rat sarcoma viral oncogene homolog (KRAS) mutation in patients with non-mucinous rectal cancer. Materials and Methods Seventy-nine patients who had pathologically confirmed rectal non-mucinous adenocarcinoma with or without KRAS-mutation and had undergone rectal MRI were divided into a training (n = 46) and validation dataset (n = 33). A texture analysis was performed on the axial T2-weighted images. The association was statistically analyzed using the Mann-Whitney U test. To extract an optimal cut-off value for the prediction of KRAS mutation, a receiver operating characteristic curve analysis was performed. The cut-off value was verified using the validation dataset. Results In the training dataset, skewness in the mutant group (n = 22) was significantly higher than in the wild-type group (n = 24) (0.221 ± 0.283; -0.006 ± 0.178, respectively, p = 0.003). The area under the curve of the skewness was 0.757 (95% confidence interval, 0.606 to 0.872) with a maximum accuracy of 71%, a sensitivity of 64%, and a specificity of 78%. None of the other texture parameters were associated with KRAS mutation (p > 0.05). When a cut-off value of 0.078 was applied to the validation dataset, this had an accuracy of 76%, a sensitivity of 86%, and a specificity of 68%. Conclusion Skewness was associated with KRAS mutation in patients with non-mucinous rectal cancer.

• Investigative Magnetic Resonance Imaging
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• v.9 no.2
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• pp.134-139
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• 2005

Purpose : To evaluate the usefulness of acoustic noise attenuator on auditory fMRI examination. Materials and methods : The acoustic noise attenuator consists of mask, earmuff and silicon earplug. The soft polyurethane sheet and polyurethane form , which has a good soundproof characteristic were used for mask and earmuff. Auditory fMRI experiments of 500 Hz pure tone stimulation were performed in three different cases; first all of mask, earmuff and earplug, secondly earmuff and earplug only and finally without attenuator in 4 normal hearing volunteers. For data acquisition, BOLD MR imaging technique was employed at a 1.5T MR scanner equipped with high performance gradient system. The raw data were analyzed using a SPM-99 analysis software and the activation maps were obtained. Results : In case of all items of acoustic attenuator used, the results revealed that activation was focused on primary auditory area. When only earmuff and earplug were used, the results showed that the activation spread over primary auditory and secondary associative areas. Last, when no device used, only weak activation was observed on the right auditory cortex. Conclusion : It is expected that the acoustic noise attenuator, which consists of earplugs, earmuffs and mask, is a very useful device in auditory fMRI study.

• Korean Journal of Radiology
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• v.24 no.12
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• pp.1190-1199
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• 2023

Objective: This study aimed to investigate the feasibility of ultrafast magnetic resonance imaging (MRI) and radiomic features derived from breast MRI for predicting the upstaging of ductal carcinoma in situ (DCIS) diagnosed using percutaneous needle biopsy. Materials and Methods: Between August 2018 and June 2020, 95 patients with 98 DCIS lesions who underwent preoperative breast MRI, including an ultrafast sequence, and subsequent surgery were included. Four ultrafast MRI parameters were analyzed: time-to-enhancement, maximum slope (MS), area under the curve for 60 s after enhancement, and time-to-peak enhancement. One hundred and seven radiomic features were extracted for the whole tumor on the first post-contrast T1WI and T2WI using PyRadiomics. Clinicopathological characteristics, ultrafast MRI findings, and radiomic features were compared between the pure DCIS and DCIS with invasion groups. Prediction models, incorporating clinicopathological, ultrafast MRI, and radiomic features, were developed. Receiver operating characteristic curve analysis and area under the curve (AUC) were used to evaluate model performance in distinguishing between the two groups using leave-one-out cross-validation. Results: Thirty-six of the 98 lesions (36.7%) were confirmed to have invasive components after surgery. Compared to the pure DCIS group, the DCIS with invasion group had a higher nuclear grade (P < 0.001), larger mean lesion size (P = 0.038), larger mean MS (P = 0.002), and different radiomic-related characteristics, including a more extensive tumor volume; higher maximum gray-level intensity; coarser, more complex, and heterogeneous texture; and a greater concentration of high gray-level intensity. No significant differences in AUCs were found between the model incorporating nuclear grade and lesion size (0.687) and the models integrating additional ultrafast MRI and radiomic features (0.680-0.732). Conclusion: High nuclear grade, larger lesion size, larger MS, and multiple radiomic features were associated with DCIS upstaging. However, the addition of MS and radiomic features to the prediction model did not significantly improve the prediction performance.

• Korean Journal of Radiology
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• v.23 no.12
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• pp.1260-1268
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• 2022

Objective: To propose standardized MRI-proton density fat fraction (PDFF) cutoff values for diagnosing hepatic steatosis, evaluated using contemporary PDFF measuring methods in a large population of healthy adults, using histologic fat fraction (HFF) as the reference standard. Materials and Methods: A retrospective search of electronic medical records between 2015 and 2018 identified 1063 adult donor candidates for liver transplantation who had undergone liver MRI and liver biopsy within a 7-day interval. Patients with a history of liver disease or significant alcohol consumption were excluded. Chemical shift imaging-based MRI (CS-MRI) PDFF and high-speed T2-corrected multi-echo MR spectroscopy (HISTO-MRS) PDFF data were obtained. By temporal splitting, the total population was divided into development and validation sets. Receiver operating characteristic (ROC) analysis was performed to evaluate the diagnostic performance of the MRI-PDFF method. Two cutoff values with sensitivity > 90% and specificity > 90% were selected to rule-out and rule-in, respectively, hepatic steatosis with reference to HFF ≥ 5% in the development set. The diagnostic performance was assessed using the validation set. Results: Of 921 final participants (624 male; mean age ± standard deviation, 31.5 ± 9.0 years), the development and validation sets comprised 497 and 424 patients, respectively. In the development set, the areas under the ROC curve for diagnosing hepatic steatosis were 0.920 for CS-MRI-PDFF and 0.915 for HISTO-MRS-PDFF. For ruling-out hepatic steatosis, the CS-MRI-PDFF cutoff was 2.3% (sensitivity, 92.4%; specificity, 63.0%) and the HISTO-MRI-PDFF cutoff was 2.6% (sensitivity, 88.8%; specificity, 70.1%). For ruling-in hepatic steatosis, the CS-MRI-PDFF cutoff was 3.5% (sensitivity, 73.5%; specificity, 88.6%) and the HISTO-MRI-PDFF cutoff was 4.0% (sensitivity, 74.7%; specificity, 90.6%). Conclusion: In a large population of healthy adults, our study suggests diagnostic thresholds for ruling-out and ruling-in hepatic steatosis defined as HFF ≥ 5% by contemporary PDFF measurement methods.

• Journal of the Korean Chemical Society
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• v.29 no.2
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• pp.80-87
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• 1985

Radiation damage in a single crystal of ammonium sulfate caused by ${\gamma}$-irradiation at room temperature has given rise to several paramagnetic centers. Electron spin resonance (ESR) spectra of crystal are obtained with the X-band EPR spectrometer at room temperature. An intense and isotropic peak of Gaussian shape at g = 2.0036 is assigned to $SO_3^-$, which shows power saturation effects. Angular dependence of spectra is studied for the rotations about three mutually perpendicular axes a, b and c. The g-values are obtained from the relative distances between isotropic peak of $SO_3^-$ and anisotropic peak of the species. Principal $g^-$values and direction cosines were calculated by diagonalizing the 3${\times}$3 matrix whose elements are the $g^-$values for each species. From the analysis of characteristic principal $g^-$values and direction cosines for ammonium sulfate single crystal, anisotropic peaks corresponding to $SO_4^-,\;SO_2^-$ and defect structure corresponding to electron excess type are identified.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.3
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• pp.343-354
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• 2012

In this paper, various spiral zeroth-order resonators are proposed for wireless power transmission. Since a zerothorder resonance(ZOR) mode of meta-material transmission lines has the characteristic of an infinite wavelength, its frequency is independent of physical length. Also, to obtain high transmission efficiencies high-Q resonators and strong coupling coefficient between coupled resonators are required. Therefore, the resonators consist of spiral inductor and lumped capacitor to use the ZOR mode and they are optimized via parametric study and circuit analysis for a high-Q resonator design. The optimized resonators are simulated and compared with a conventional spiral resonator and one of them was fabricated and measured. The fabricated one has a dimension of $20cm{\times}20cm{\times}8cm$($0.009{\lambda}_0{\times}0.009_{\lambda}_0{\times}0.004{\lambda}_0$) and the transmission efficiency of 80 % is measured at 13.56 MHz at transmitted distance of 40 cm.

• Journal of Korean Neurosurgical Society
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• v.44 no.4
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• pp.240-244
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• 2008

Objective : Sotos Syndrome is characterized by macrocephaly, overgrowth, and developmental delay, and more than 300 patients have been reported worldwide to date. The authors reviewed the clinical characteristics of 8 patients with Sotos Syndrome in Korea for a new understanding and treatment strategies. Methods : The medical records of a total of eight Korean children with Sotos Syndrome were reviewed. All patients underwent developmental checkup, lumbar punctures for measurement of intracranial pressure (ICP), brain and spine magnetic resonance imaging and computerized tomography. Results : All 8 patients showed macrocephaly and the characteristic craniofacial features of Sotos Syndrome. Other clinical characteristics shown were overgrowth (7/8), developmental delay (7/8), congenital heart defect (3/8), flat foot (8/8), scoliosis (4/8), spina bifida (8/8), hydrocephalus (4/8), cavum vergae (3/8), and increased subdural fluid collection (5/8). Mean ICP measured via lumbar puncture was $27.35{\pm}6.25\;cm$ $H_2O$ (range 20 to 36 cm $H_2O$). Two patients received ventriculo-peritoneal shunt, and 1 patient underwent subduro-peritoneal shunt with improvement. Spinal orthosis was applied to 4/5 patients with scoliosis and 4/8 children with flat foot were provided with foot orthosis. Conclusion : In this first Korean study of 8 Sotos Syndrome patients we demonstrated the presence of spina bifida and increased ICP, which had not been previously described. The authors therefore suggest that all patients with Sotos Syndrome should undergo examination for the presence of spina bifida, and that shunt procedures would improve development and alleviate clinical symptoms.

• Journal of Microbiology and Biotechnology
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• v.20 no.7
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• pp.1061-1068
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• 2010

The biological synthesis of nanoparticles has gained considerable attention in view of their excellent biocompatibility and low toxicity. We isolated and purified rhamnolipids from Pseudomonas aeruginosa strain BS-161R, and these purified rhamnolipids were used to synthesize silver nanoparticles. The purified rhamnolipids were further characterized and the structure was elucidated based on one- and two-dimensional $^1H$ and $^{13}C$ NMR, FT-IR, and HR-MS spectral data. Purified rhamnolipids in a pseudoternary system of n-heptane and water system along with n-butanol as a cosurfactant were added to the aqueous solutions of silver nitrate and sodium borohydride to form reverse micelles. When these micelles were mixed, they resulted in the rapid formation of silver nanoparticles. The synthesized nanoparticles were characterized by UV-Visible spectroscopy, transmission electron microscopy, and energy dispersive X-ray spectroscopy (EDS). The nanoparticles formed had a sharp adsorption peak at 410 nm, which is characteristic of surface plasmon resonance of the silver nanoparticles. The nanoparticles were monodispersed, with an average particle size of 15.1 nm (${\sigma}={\pm}5.82$ nm), and spherical in shape. The EDS analysis revealed the presence of elemental silver signal in the synthesized nanoparticles. The formed silver nanoparticles exhibited good antibiotic activity against both Grampositive and Gram-negative pathogens and Candida albicans, suggesting their broad-spectrum antimicrobial activity.

• Journal of Sensor Science and Technology
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• v.26 no.4
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• pp.235-238
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• 2017

In this study, the design of a tri-axis micromachined gyroscope is proposed and the vibration characteristic of the structure is analyzed. Tri-axis vibratory gyroscopes that utilize Coriolis effect are the most commonly used micromachined inertial sensors because of their advantages, such as low cost, small packaging size, and low power consumption. The proposed design is a single structure with four proof masses, which are coupled to their adjacent ones. The coupling springs of the proof masses orthogonally transfer the driving vibrational motion. The resonant frequencies of the gyroscope are analyzed by finite element method (FEM) simulation. The suspension beam spring design of proof masses limits the resonance frequencies of four modes, viz., drive mode, pitch, roll and yaw sensing mode in the range of 110 Hz near 21 kHz, 21173 Hz, 21239 Hz, 21244 Hz, and 21280 Hz, respectively. The unwanted modes are separated from the drive and sense modes by more than 700 Hz. Thereafter the drive and the sense mode vibrations are calculated and simulated to confirm the driving feasibility and estimate the sensitivity of the gyroscope. The cross-axis sensitivities caused by driving motion are 1.5 deg/s for both x- and y-axis, and 0.2 deg/s for z-axis.

• Korean Journal of Radiology
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• v.22 no.4
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• pp.525-534
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• 2021

Objective: To assess the effect of left atrial appendage (LAA) isolation on LAA emptying and left atrial (LA) function using cardiac MRI in patients who underwent successful catheter ablation of atrial fibrillation (AF). Materials and Methods: This retrospective study included 84 patients (mean age, 59 ± 10 years; 67 males) who underwent cardiac MRI after successful catheter ablation of AF. According to the electrical activity of LAA after catheter ablation, patients showed either LAA isolation or LAA normal activity. The LAA emptying phase (LAA-EP, in the systolic phase [SP] or diastolic phase), LAA emptying flux (LAA-EF, mL/s), and LA ejection fraction (LAEF, %) were evaluated by cardiac MRI. Results: Of the 84 patients, 61 (73%) and 23 (27%) patients showed LAA normal activity and LAA isolation, respectively. Incidence of LAA emptying in SP was significantly higher in LAA isolation (91% vs. 0%, p < 0.001) than in LAA normal activation. LAA-EF was significantly lower in LAA isolation (40.1 ± 16.2 mL/s vs. 80.2 ± 25.1 mL/s, p < 0.001) than in LAA normal activity. Furthermore, LAEF was significantly lower in LAA isolation (23.7% ± 11.2% vs. 31.1% ± 16.6%, p = 0.04) than in LAA normal activity. Multivariate analysis demonstrated that the LAA-EP was independent from LAEF (p = 0.01). Conclusion: LAA emptying in SP may be a critical characteristic of LAA isolation, and it may adversely affect the LAEF after catheter ablation of AF.