• Korean Journal of Remote Sensing
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• v.37 no.6_3
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• pp.2035-2046
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• 2021

Glacier movement speed is the most basic measurement for glacial dynamics research and is a very important indicator in predicting sea level rise due to climate change. In this study, the two-dimensional velocity measurements of Campbell Glacier located in Terra Nova Bay in East Antarctica were observed through the SAR offset tracking technique. For this purpose, domestic KOMPSAT-5 SAR satellite images taken on July 9, 2021 and August 6, 2021 were acquired. The Multi-kernel SAR offset tracking proposed through previous studies is a technique to obtain the optimal result that satisfies both resolution and precision. However, since offset tracking is repeatedly performed according to the size of the kernel, intensive computational power and time are required. Therefore, in this study, we strategically proposed a coarse-to-fine offset tracking approach. Through coarse-to-fine SAR offset tracking, it is possible to obtain a result with improved observation precision (especially, about 4 times in azimuth direction) while maintaining resolution compared to general offset tracking results. Using this proposed technique, a two-dimensional velocity measurements of Campbell Glacier were generated. As a result of analyzing the two-dimensional movement velocity image, it was observed that the grounding line of Campbell Glacier exists at approximately latitude -74.56N. The flow velocity of Campbell Glacier Tongue analyzed in this study (185-237 m/yr) increased compared to that of 1988-1989 (140-240 m/yr). And compared to the flow velocity (181-268 m/yr) in 2010-2012, the movement speed near the ground line was similar, but it was confirmed that the movement speed at the end of the Campbell Glacier Tongue decreased. However, there is a possibility that this is an error that occurs because the study result of this study is an annual rate of glacier movement that occurred for 28 days. For accurate comparison, it will be necessary to expand the data in time series and accurately calculate the annual rate. Through this study, the two-dimensional velocity measurements of the glacier were observed for the first time using the KOMPSAT-5 satellite image, a domestic X-band SAR satellite. It was confirmed that the coarse-to-fine SAR offset tracking approach of the KOMPSAT-5 SAR image is very useful for observing the two-dimensional velocity of glacier movements.

• Korean Journal of Mineralogy and Petrology
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• v.34 no.2
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• pp.133-146
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• 2021

Aragonite is one of common polymorphs of calcium carbonate (CaCO₃) and formed via biological or physical processes through precipitation in many different environments including marine ecosystems. It is noted that aragonite formation and growth as well as the substitution of trace elements such as strontium (Sr) in the aragonite structure would be dependant on several key parameters such as concentrations of chemical species and temperature. In this study, properties of the incorporation of Sr into aragonite were investigated over a wide range of various saturation conditions and temperatures similar to the marine ecosystem. All pure aragonite samples were inorganically synthesized through a constant-addition method with varying concentrations of the reactive species ([Ca]=[CO₃] 0.01-1 M), injection rates of the reaction solution (0.085-17 mL/min), and solution temperatures (5-40 ℃). Pure aragonite was also formed even under the Sr incorporation conditions (0.02-0.5 M, 15-40 ℃). When temperature and saturation index (SI) with respect to aragonite increased, the crystallinity and the crystal size of aragonite increased indicating the growth of aragonite crystal. However, it was difficult to interpret the crystal growth rate because the crystal growth rate calculated using BET-specific surface area was significantly influenced by the crystal morphology. The distribution coefficient of Sr (K_Sr) into aragonite decreased from 2.37 to 1.57 with increasing concentrations of species (Ca²⁺ and CO₃^2-) at a range of 0.02-0.5 M. Similarly, it was also found that K_Sr decreased 1.90 to 1.54 at a range of 15-40 ℃. All K_Sr values are greater than 1, and the inverse correlation between the K_Sr and the crystal growth rate indicate that Sr incorporation into aragonite is in a compatible relationship.

• The Journal of Korean Society for Radiation Therapy
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• v.32
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• pp.31-39
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• 2020

Purpose: The aims of this study were to compare the superficial dose with Optically Stimulated Luminescence Dosimeter(OSLD) measurement and Treatment Planning System(TPS) calculation for 6MV-Flattening Filter Free(FFF) energy using HalcyonTM and TrueBeamTM. Materials and methods: Phantom study was performed using the CT images of human phantom. In the treatment planning system, the Planning Target Volume(PTV) was contoured which is similar to Glottic cancer. Furthermore, Point(M), Point(R), and Point(L) were contoured at the iso-center of head and neck region and 5mm bolus was applied to the body contour. Each treatment plans using 6MV-FFF energy from HalcyonTM and TrueBeamTM with static Intensity Modulated Radiation Therapy(IMRT) and Volumetric Modulated Arc Therapy(VMAT) were established with eclipse. To reproduce the same position as the TPS, OSLDs were placed at the iso-center point and 5mm bolus was applied to compare the error rate after the dose delivery. Result: The results of the study using human phantom are as follows. In case of HalcyonTM, the mean absolute error rates of the point dose using the treatment planning system and the dose measured by OSLD were 1.7%±1.2% for VMAT and 4.0±2.8% for IMRT. Also TrueBeamTM was identified as 2.4±0.4% and 8.6±1.8% respectively for VMAT and IMRT. Conclusion: Through the results of this study, TrueBeamTM confirmed that the average error rate was 2.4 times higher for VMAT and 3.6 times higher for IMRT than HalcyonTM. Therefore, based on the results of this study, If we need a more accurate dose assessment for the superficial dose, It is expected that using HalcyonTM would be better than TrueBeamTM.

• Korean Journal of Agricultural and Forest Meteorology
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• v.24 no.1
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• pp.13-34
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• 2022

Soil moisture data have been collected at 11 agrometeorological stations operated by The Korea Meteorological Administration (KMA). This study aimed to verify the accuracy of soil moisture data of KMA and develop a correction formula to be applied to improve their quality. The soil of the observation field was sampled to analyze its physical properties that affect soil water content. Soil texture was classified to be sandy loam and loamy sand at most sites. The bulk density of the soil samples was about 1.5 g/cm³ on average. The content of silt and clay was also closely related to bulk density and water holding capacity. The EnviroSCAN model, which was used as a reference sensor, was calibrated using the self-manufactured "reference soil moisture observation system". Comparison between the calibrated reference sensor and the field sensor of KMA was conducted at least three times at each of the 11 sites. Overall, the trend of fluctuations over time in the measured values of the two sensors appeared similar. Still, there were sites where the latter had relatively lower soil moisture values than the former. A linear correction formula was derived for each site and depth using the range and average of the observed data for the given period. This correction formula resulted in an improvement in agreement between sensor values at the Suwon site. In addition, the detailed approach was developed to estimate the correction value for the period in which a correction formula was not calculated. In summary, the correction of soil moisture data at a regular time interval, e.g., twice a year, would be recommended for all observation sites to improve the quality of soil moisture observation data.

• Economic and Environmental Geology
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• v.56 no.3
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• pp.277-291
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• 2023

To analyze the crustal velocity structures beneath 21 broadband seismic stations in Gangwon Province, South Korea, we first applied the H-κ stacking method to 139 teleseismic event data (Mw ≥ 5.8 and the epicentral distance of 30° - 90°) occurring between March 18, 2019 and December 31, 2022 to estimate the Moho depths and V_p/V_s ratios beneath each station. The Moho depths and V_p/V_s ratios from the H-κ stacking method range from 24.9 to 33.2 km depth and 1.695 - 1.760, respectively, and the estimated V_p/V_s ratios were applied to the joint inversion of receiver functions and surface wave dispersion to obtain 1-D crustal velocity models beneath each station. The resulting Moho depths range from 25.9 to 33.7 km depth, similar to the results from the H-κ stacking method. Moho depth results from the both methods are generally consistent with Airy's isostasy. The 1-D crustal velocity models confirm that the existence of 2 km thick low-velocity layers with P-wave velocities of 5 km/s or less at some stations in the Taebaeksan basin, and at the stations CHNB and GAPB in northern Gangwon Province, which are located above the Cenozoic sedimentary layer. The station SH2B, although not overlying a sedimentary layer, has a low P-wave velocity near the surface, which is probably due to various factors such as weathering of the bedrock. We also observe a velocity inversion with decreasing velocity with depth at all stations within 4 - 12 km depths, and mid-crustal discontinuities possibly due to density differences in the rocks at around 10 km depth below some stations.

• Journal of the Korean Society of Radiology
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• v.83 no.2
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• pp.331-343
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• 2022

Purpose To systematically compare the performance of liver imaging reporting and data system treatment response (LR-TR) with the modified Response Evaluation Criteria in Solid Tumors (mRECIST) for diagnosing viable hepatocellular carcinoma (HCC) treated with locoregional therapy (LRT). Materials and Methods Original studies of intra-individual comparisons between the diagnostic performance of LR-TR and mRECIST using dynamic contrast-enhanced CT or MRI were searched in MEDLINE and EMBASE, up to August 25, 2021. The reference standard for tumor viability was surgical pathology. The meta-analytic pooled sensitivity and specificity of the viable category using each criterion were calculated using a bivariate random-effects model and compared using bivariate meta-regression. Results For five eligible studies (430 patients with 631 treated observations), the pooled per-lesion sensitivities and specificities were 58% (95% confidence interval [CI], 45%-70%) and 93% (95% CI, 88%-96%) for the LR-TR viable category and 56% (95% CI, 42%-69%) and 86% (95% CI, 72%-94%) for the mRECIST viable category, respectively. The LR-TR viable category provided significantly higher pooled specificity (p < 0.01) than the mRECIST but comparable pooled sensitivity (p = 0.53). Conclusion The LR-TR algorithm demonstrated better specificity than mRECIST, without a significant difference in sensitivity for the diagnosis of pathologically viable HCC after LRT.

• Journal of the Korean Society of Radiology
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• v.82 no.4
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• pp.889-902
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• 2021

Purpose To assess the diagnostic performance of contrast-enhanced ultrasound (CEUS) for additional MR-detected enhancing lesions and to determine whether or not kinetic pattern results comparable to dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) of the breast can be obtained using the quantitative analysis of CEUS. Materials and Methods In this single-center prospective study, a total of 71 additional MR-detected breast lesions were included. CEUS examination was performed, and lesions were categorized according to the Breast Imaging-Reporting and Data System (BI-RADS). The sensitivity, specificity, and diagnostic accuracy of CEUS were calculated by comparing the BI-RADS category to the final pathology results. The degree of agreement between CEUS and DCE-MRI kinetic patterns was evaluated using weighted kappa. Results On CEUS, 46 lesions were assigned as BI-RADS category 4B, 4C, or 5, while 25 lesions category 3 or 4A. The diagnostic performance of CEUS for enhancing lesions on DCE-MRI was excellent, with 84.9% sensitivity, 94.4% specificity, and 97.8% positive predictive value. A total of 57/71 (80%) lesions had correlating kinetic patterns and showed good agreement (weighted kappa = 0.66) between CEUS and DCE-MRI. Benign lesions showed excellent agreement (weighted kappa = 0.84), and invasive ductal carcinoma (IDC) showed good agreement (weighted kappa = 0.69). Conclusion The diagnostic performance of CEUS for additional MR-detected breast lesions was excellent. Accurate kinetic pattern assessment, fairly comparable to DCE-MRI, can be obtained for benign and IDC lesions using CEUS.

• The Korean Journal of Nuclear Medicine
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• v.32 no.6
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• pp.490-496
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• 1998

Purpose: We evaluated brain perfusion SPECT findings of MELAS syndrome and mitochondrial myopathy in correlation with MR imaging in search of specific imaging features. Materials and Methods: Subjects were five patients (four females and one male; age range, 1 to 25 year) who presented with repeated stroke-like episodes, seizures or developmental delay or asymptomatic but had elevated lactic acid in CSF and serum. Conventional non-contrast MR imaging and Tc-99m-ethyl cysteinate dimer (ECD) brain perfusion SPECT were Performed and imaging features were analyzed. Results: MRI demonstrated increased T2 signal intensities in the affected areas of gray and white matters mainly in the parietal (4/5) and occipital lobes (4/5) and in the basal ganglia (1/5), which were not restricted to a specific vascular territory. SPECT demonstrated decreased perfusion in the corresponding regions of MRI lesions. In addition, there were perfusion defects in parietal (1 patient), temporal (2), and frontal (1) lobes and basal ganglia (1) and thalami (2). In a patient with mitochondrial myopathy who had normal MRI, decreased perfusion was noted in left parietal area and bilateral thalami. Conclusion: Tc-99m ECD SPECT imaging in patients with MELAS syndrome and mitochondrial myopathy showed hypoperfusion of parieto-occipital cortex, basal ganglia, thalamus and temporal cortex, which were not restricted to a specific vascular territory. There were no specific imaging features on SPECT. The significance of abnormal perfusion on SPECT without corresponding MR abnormalities needs to be evaluated further in larger number of patients.

• Radiation Oncology Journal
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• v.20 no.4
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• pp.343-352
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• 2002

Purpose : Radiotherapy is the main treatment modality for uterine cervix cancer. Since the rectum is in the radiation target volume, rectal bleeding is a common late side effect. This study evaluates the risk factors of radiation induced rectal bleeding and discusses its optimal management. Materials and Methods : total of 213 patients who completed external beam radiation therapy (EBRT) and intracavitary radiation (ICR) between September 1994 and December 1999 were included in this study. No patient had undergone concurrent chemo-radiotherapy. Ninety patients received radiotherapy according to a modified hyperfractionated schedule. A midline block was placed at a pelvic dose of between 30.6 Gy to 39.6 Gy. The total parametrial dose from the EBRT was 51 to 59 Gy depending on the extent of their disease. The Point A dose from the HDR brachytherapy was 28 Gy to 30 Gy $(4\;Gy\times7,\;or\;5\;Gy\times6)$. The rectal point dose was calculated either by the ICRU 38 guideline, or by anterior rectal wall point seen on radiographs, with barium contrast. Rectal bleeding was scored by the LENT/SOMA criteria. For the management of rectal bleeding, we opted for observation, sucralfate enema or coagulation based on the frequency or amount of bleeding. The median follow-up period was 39 months $(12\~86\;months)$. Results : The incidence of rectal bleeding was $12.7\%$ (27/213); graded as 1 in 9 patients, grade 2 in 16 and grade 3 in 2. The overall moderate and severe rectal complication rate was $8.5\%$. Most complications $(92.6\%)$ developed within 2 years following completion of radiotherapy (median 16 months). No patient progressed to rectal fistula or obstruction during the follow-up period. In the univariate analysis, three factors correlated with a high incidence of bleeding an icruCRBED greater than 100 Gy $(19.7\%\;vs.\;4.2\%)$, an EBRT dose to the parametrium over 55 Gy $(22.1\%\;vs.\;5.1\%)$ and higher stages of III and IV $(31.8\%\;vs.\;10.5\%)$. In the multivariate analysis, the icruCRBED was the only significant factor (p>0.0432). The total parametrial dose from the EBRT had borderline significance (p=0.0546). Grade 1 bleeding was controlled without further management (3 patients), or with sucralfate enema 1 to 2 months after treatment. For grade 2 bleeding, sucralfate enema for 1 to 2 months reduced the frequency or amount of bleeding but for residual bleeding, additional coagulation was peformed, where immediate cessation of bleeding was achieved (symptom duration of 3 to 10 months). Grade 3 bleeding lasted for 1 year even with multiple transfusions and coagulations. Conclusion : Moderate and several rectal bleeding occurred in $8.5\%$ of patients, which is comparable with other reports. The most significant risk factor for rectal bleeding was the accumulated dose to the rectum (icruCRBED), which corrected with consideration to biological equivalence. Prompt management of rectal bleeding, with a combination of sucralfate enema and coagulation, reduced the duration of the symptom, and minimized the anxiety/discomfort of patients.

• The Journal of Korean Society for Radiation Therapy
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• v.32
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• pp.17-29
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• 2020

Purpose: The purpose of this work was to investigate the dosimetric impact of mixed energy partial arc technique on prostate cancer VMAT. Materials and Methods: This study involved prostate only patients planned with 70Gy in 30 fractions to the planning target volume (PTV). Femoral heads, Bladder and Rectum were considered as oragan at risk (OARs). For this study, mixed energy partial arcs (MEPA) were generated with gantry angle set to 180°~230°, 310°~50° for 6MV arc and 130°~50°, 310°~230° for 15MV arc. Each arc set the avoidance sector which is gantry angle 230°~310°, 50°~130° at first arc and 50°~310° at second arc. After that, two plans were summed and were analyzed the dosimetry parameter of each structure such as Maximum dose, Mean dose, D2%, Homogeneity index (HI) and Conformity Index (CI) for PTV and Maximum dose, Mean dose, V70Gy, V50Gy, V30Gy, and V20Gy for OARs and Monitor Unit (MU) with 6MV 1 ARC, 6MV, 10MV, 15MV 2 ARC plan. Results: In MEPA, the maximum dose, mean dose and D2% were lower than 6MV 1 ARC plan(p<0.0005). However, the average difference of maximum dose was 0.24%, 0.39%, 0.60% (p<0.450, 0.321, 0.139) higher than 6MV, 10MV, 15MV 2 ARC plan, respectively and D2% was 0.42%, 0.49%, 0.59% (p<0.073, 0.087, 0.033) higher than compared plans. The average difference of mean dose was 0.09% lower than 10MV 2 ARC plan, but it is 0.27%, 0.12% (p<0.184, 0.521) higher than 6MV 2 ARC, 15MV 2 ARC plan, respectively. HI was 0.064±0.006 which is the lowest value (p<0.005, 0.357, 0.273, 0.801) among the all plans. For CI, there was no significant differences which were 1.12±0.038 in MEPA, 1.12±0.036, 1.11±0.024, 1.11±0.030, 1.12±0.027 in 6MV 1 ARC, 6MV, 10MV, 15MV 2 ARC, respectively. MEPA produced significantly lower rectum dose. Especially, V70Gy, V50Gy, V30Gy, V20Gy were 3.40, 16.79, 37.86, 48.09 that were lower than other plans. For bladder dose, V30Gy, V20Gy were lower than other plans. However, the mean dose of both femoral head were 9.69±2.93, 9.88±2.5 which were 2.8Gy~3.28Gy higher than other plans. The mean MU of MEPA were 19.53% lower than 6MV 1 ARC, 5.7% lower than 10MV 2 ARC respectively. Conclusion: This study for prostate radiotherapy demonstrated that a choice of MEPA VMAT has the potential to minimize doses to OARs and improve homogeneity to PTV at the expense of a moderate increase in maximum and mean dose to the femoral heads.