• Korean Journal of Radiology
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• v.22 no.9
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• pp.1547-1554
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• 2021

Objective: We aimed to investigate whether repeated intravascular administration of iodinated contrast media (ICM) or gadolinium-based contrast agents (GBCAs) within a short interval was associated with an increased risk of post-contrast acute kidney injury (PC-AKI). Materials and Methods: This retrospective study included 300 patients (mean age ± standard deviation, 68.5 ± 8.1 years; 131 male and 169 female) who had undergone at least one ICM-enhanced perfusion brain CT scan, had their baseline and follow-up serum creatinine levels available, and had not undergone additional contrast-enhanced examinations 72 hours before and after a time window of interest were included. The study population was divided into three groups: single-dose group and groups of patients who had received multiple contrast administrations in the time window of interest with the minimum contrast repeat interval either within 4 hours (0-4-hour group) or between 4 to 48 hours (4-48-hour group). Multivariable logistic regression analysis was conducted to evaluate the association between AKI and repeated ICM administrations. A similar supplementary analysis was performed including both ICM and GBCA. Results: When ICM was only considered ignoring GBCA, among 300 patients, 207 patients received a single dose of ICM, 58 had repeated doses within 4 hours (0-4-hour group), and 35 patients had repeated doses between 4 to 48 hours (4-48-hour group). Most patients (> 95%) had a baseline estimated glomerular filtration rate (eGFR) of ≥ 30 mL/min/1.73 m². AKI occurred in 7.2%, 13.8%, and 8.6% of patients in the single-dose, 0-4-hour, and 4-48-hour groups, respectively. In the 0-4-hour and 4-48-hour groups, additional exposure to ICM was not associated with AKI after adjusting for comorbidities and nephrotoxic drugs (all p values > 0.05). Conclusion: Repeated intravascular administrations of ICM within a short interval did not increase the risk of AKI in our study patients suspected of acute stroke with a baseline eGFR of ≥ 30 mL/min/1.73 m².

• Journal of the Korean Society of Radiology
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• v.84 no.6
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• pp.1324-1336
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• 2023

Purpose This study aimed to compare the diagnostic performance of cardiac CT and transthoracic echocardiogram (TTE) depending on the degree of valvular calcification and bicuspid aortic valve (BAV) subtype. Materials and Methods This retrospective study included 266 consecutive patients (106 with BAV and 160 with tricuspid aortic valve) who underwent cardiac CT and TTE before aortic valve replacement. Cardiac CT was used to evaluate the morphology of the aortic valve, and a calcium scoring scan was used to quantify valve calcium. The aortic valves were classified into fused and two-sinus types. The diagnostic accuracy of cardiac CT and TTE was calculated using a reference standard for intraoperative inspection. Results CT demonstrated significantly higher sensitivity, negative predictive value, and accuracy than TTE in detecting BAV (p < 0.001, p < 0.001, and p = 0.003, respectively). The TTE sensitivity tended to decrease as valvular calcification increased. The error rate of TTE for CT was 10.9% for the twosinus type of BAV and 28.3% for the fused type (p = 0.044). Conclusion Cardiac CT had a higher diagnostic performance in detecting BAV than TTE and may help diagnose BAV, particularly in patients with severe valvular calcification.

• Journal of the Korean Society of Radiology
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• v.83 no.1
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• pp.138-148
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• 2022

Purpose This study evaluated the rates and annual trends of pediatric CT scans in South Korea using a nationwide population-based database. Materials and Methods Data regarding pediatric CT scan usage between 2012 and 2017 were retrieved from the health insurance review and assessment service. Data on the age, sex, diagnosis, and the anatomical area of involved patients were also extracted. Results A total of 576376 CT examinations were performed among 58527528 children aged below 18 years (9.8 scans/1000 children), and the number of CT examinations per 1000 children was noted to have increased by 23.2% from 9.0 in 2012 to 11.0 in 2017. Specifically, the number of CT examinations increased by 32.9% for the 6-12 years of age group (7.4/1000 to 9.8/1000) and by 34.0% for the 13-18 years of age group (11.4/1000 to 15.3/1000). Moreover, majority of the CT scans were limited to the head (39.1%), followed by the extremities (32.5%) and the abdomen (13.7%). Notably, the number of extremity CT scans increased by 83.6% (2.3/1000 to 4.2/1000), and its proportion as compared to other scans increased from 25.3% to 37.7%. Conclusion CT scans in the pediatric population increased continuously from 2012 to 2017 at an annual rate of 4.4%. Therefore, physicians should balance the benefits of CT with its potential harms from associated radiation exposure in pediatric patients.

• Applied Chemistry for Engineering
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• v.35 no.4
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• pp.296-302
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• 2024

An ionic conjugated polymer-iron (III) chloride composite was prepared via in-situ quaternization polymerization of 2-ethynylpyridine (2EP) using iron (III) chloride. Various instrumental methods revealed that the chemical structure of the resulting conjugated polymer (P2EP)-iron (III) chloride composite has the conjugated backbone system having the designed pyridinium ferric chloride complexes. The polymerization mechanism was assumed to be that the activated triple bond of 2-ethynylpyridinium salt, formed at the first reaction step, is easily susceptible to the step-wise polymerization, followed by the same propagation step that contains the propagating macroanion and monomeric 2-ethynylpyridinium salts. The electro-optical and electrochemical properties of the P2EP-FeCl₃ composite were studied. In the UV-visible spectra of P2EP-FeCl₃ composite, the absorption maximum values were 480 nm and 533 nm, and the PL maximum value was 598 nm. The cyclic voltammograms of the P2EP-FeCl₃ composite exhibited irreversible electrochemical behavior between the oxidation and reduction peaks. The kinetics of the redox process of composites were found to be very close to a diffusion-controlled process from the plot of the oxidation current density versus the scan rate.

• Journal of Chest Surgery
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• v.43 no.6
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• pp.635-641
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• 2010

Background: Radiofrequency endovenous ablation of incompetent saphenous vein has gaining popularity over the conventional ligation and stripping as a minimally invasive technique. The latest version of radiofrequency endovenous catheter, $VNUS^{\circledR}Colosure$ fast VNUS medical Technologies, San Jose, CA, adopted a segmental ablation system, instead of continous pullback, is designed to reduce treatment time in comparison with the previous model $VNUS^{\circledR}Colosure$ plus VNUS medical Technologies, San Jose, CA. The purpose of this study is to compare the difference between two endovenous radiofrequency ablation systems in terms of treatment efficacy and complication rates. We analyze the initial efficacy and complication rates of $VNUS^{\circledR}Colosure$ fast with $VNUS^{\circledR}Colosure$ plus. Material and Method: Between June 2006 and August 2009, $VNUS^{\circledR}Colosure$ plus was performed to treat varicose vein on 59 limbs in 41. patients and $VNUS^{\circledR}Colosure$ fast was performed on 76 limbs in 67 patients. We retrospectively compared in both group with sex, mean treatment time, mean treatment diameter, conjugated treatment, and complications after the procedure. Result: All patient were symptomatic and diagnosed as varicose vein and underwent level 2 clinical classification with color duplex scan. The mean treatment time for the great saphenous vein was significantly less with $VNUS^{\circledR}Colosure$ fast ($17.0{\pm}6.5min$) than $VNUS^{\circledR}Colosure$ plus ($62.7{\pm}9.8min$). There was no significant difference in 1 yr closure rate between groups (p=0.32). Minor complications such as skin burn, thrombophlebitis, ecchymosis, hematoma, cellulitis, tenderness, and there were not different between the groups. Conclusion: Both $VNUS^{\circledR}Colosure$ fast and $VNUS^{\circledR}Colosure$ plus are effective methods of endovenous saphenous ablation. $VNUS^{\circledR}Colosure$ fast is superior to the previous model with less treatment time preserving compatible efficacy and complications. The efficacy of $VNUS^{\circledR}Colosure$ fast for long term closure rate remains to be established.

• Investigative Magnetic Resonance Imaging
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• v.13 no.2
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• pp.161-170
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• 2009

Purpose : A parallel imaging method provides us to improve temporal resolution to obtain three-dimensional (3D) MR images. The objective of this study was to optimize three 3D MRI techniques by adjusting 2D SESNE factors of the parallel imaging method in phantom and human brain. Materials and Methods : With a 3 Tesla MRI system and an 8-channel phase-array sensitivity-encoding (SENSE) coil, three 3D MRI techniques of 3D T1-weighted imaging (3D T1WI), 3D T2-weighted imaging (3D T2WI) and 3D fluid attenuated inversion recovery (3D FLAIR) imaging were optimized with adjusting SESNE factors in a water phantom and three human brains. The 2D SENSE factor was applied on the phase-encoding and the slice-encoding directions. Signal-to-noise ratio(SNR), percent signal reduction rate(%R), and contrast-to-noise ratio(CNR) were calculated by using signal intensities obtained in specific regions-of-interest (ROI). Results : In the phantom study, SENSE factor = 3 was provided in 0.2% reduction of signals against without using SENSE with imaging within 5 minutes for 3D T1WI. SENSE factor = 2 was provided in 0.98% signal reduction against without using SENSE with imaging within 5 minutes for 3D T2WI. SENSE factor = 4 was provided in 0.2% signal reduction against without using SENSE with imaging around 6 minutes for 3D FLAIR. In the human brain study, SNR and CNR were higher with SENSE factors = 3 than 4 for all three imaging techniques. Conclusion : This study was performed to optimize 2D SENSE factors in the three 3D MRI techniques that can be scanned in clinical time limitations with minimizing SNR reductions. Without compromising SNR and CNR, the optimum 2D SENSE factors were 3 and 4, yielding the scan time of about 5 to 6 minutes. Further studies are necessary to optimize 3D MRI techniques in other areas in human body.

• Childhood Kidney Diseases
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• v.3 no.2
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• pp.187-195
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• 1999

Purpose : VUR is state where urine regurge from bladder to ureter and kidney. It is shown in about 1/3 of urinary tract infection patients and it is classified as grade I to V. We compared results from RI VCUG(Radiisotope voiding cystourethrography) and X-ray VCUG which used in diagnosing VUR in children, to evaluate which is better in diagnosing VUR in children. Methods : 41 Patients(19 males, 21 females), who visited Pediatric department, Soonchunhyang university Hospital from peroid of 1991. January to 1998. July for recurrent urinary tract infection or abnormalities in ultrasonogams, were enrolled in the study. The age ranged from 9 months to 17 years and mean age was 5 1/2 years. Both RI VCUG and X-ray VCUG were done and follow-up test of urine culture, renal ultrasonogram and RI VCUG were done every month, every 3 month and every 6 month, respectively to observe the disappearance of VUR and evaluated the prognosis. Results : 24 patients had taken RI VCUG and 17(70.1%) patients showed positive result. 22 patients had taken X-ray VCUG and 9(40.1%) patients showed findings of VUR. 17 patients had taken both tests and 14 patients showed positive result in RI VCUG and 6 of these patients also showed reflux in X-ray VCUG. 3 patients who showed negative in RI VCUG, showed negative also in X-ray VCUG. For prognosis, resolution and scar formation was shown in 8 patients each. Persistent VUR was shown in 6 patients and 2 of these patients VUR was corrected by operation, 1 patient showed decreased renal function, and 1 patient was not follwed up. 8 of 9 patients who showed findings of VUR on DMSA scan formed a scar and 8 patients who showed no findings of VUR didn't form a scar. Urine culture was positive in 17 of 19 patients with VUR. Positive rate in urine culture was higher than that of patients with no VUR who showed positivity in 15 of 21 patients for urine culture. E. coli was most common organism and the period free of UTI was 14 months in VUR patients and it was shorter compared to patients without VUR which was 26 months. Conclusion : In diagnosing VUR in children, the positive rate was higher in RI VCUG than X-ray VCUG. Therefore, in early diagnosis when VUR is suspicious but not shown in X-ray VCUG, RI VCUG should be done and it will help to make accurate diagnosis.

• Journal of radiological science and technology
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• v.36 no.4
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• pp.291-297
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• 2013

This study is aimed to evaluate the effect of $T_{1/2}$ upon count rates in the analysis of dynamic scan using NaI (Tl) scintillation camera, and suggest a new quality control method with this effects. We producted a point source with $^{99m}TcO_4^-$ of 18.5 to 185 MBq in the 2 mL syringes, and acquired 30 frames of dynamic images with 10 to 60 seconds each using Infinia gamma camera (GE, USA). In the second experiment, 90 frames of dynamic images were acquired from 74 MBq point source by 5 gamma cameras (Infinia 2, Forte 2, Argus 1). There were not significant differences in average count rates of the sources with 18.5 to 92.5 MBq in the analysis of 10 to 60 seconds/frame with 10 seconds interval in the first experiment (p>0.05). But there were significantly low average count rates with the sources over 111 MBq activity at 60 seconds/frame (p<0.01). According to the second analysis results of linear regression by count rates of 5 gamma cameras those were acquired during 90 minutes, counting efficiency of fourth gamma camera was most low as 0.0064%, and gradient and coefficient of variation was high as 0.0042 and 0.229 each. We could not find abnormal fluctuation in $x^2$ test with count rates (p>0.02), and we could find the homogeneity of variance in Levene's F-test among the gamma cameras (p>0.05). At the correlation analysis, there was only correlation between counting efficiency and gradient as significant negative correlation (r=-0.90, p<0.05). Lastly, according to the results of calculation of $T_{1/2}$ error from change of gradient with -0.25% to +0.25%, if $T_{1/2}$ is relatively long, or gradient is high, the error increase relationally. When estimate the value of 4th camera which has highest gradient from the above mentioned result, we could not see $T_{1/2}$ error within 60 minutes at that value. In conclusion, it is necessary for the scintillation gamma camera in medical field to manage hard for the quality of radiation measurement. Especially, we found a tendency that count rate changes over time at this study, and we proved that it can effect $T_{1/2}$. And also, there is need of appropriate phantoms and the method of quality management like this study, because there are not any advice or limitation degrees for domestic medical purpose scintillation camera.

• Radiation Oncology Journal
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• v.4 no.1
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• pp.35-43
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• 1986

Study patients with head and neck carcinoma were studied retrospectively to assess the impact of treatment on survival and local control rate by stage in the Dept of Radiation Therapy, Korea University Hae Wha Hospital between March 1981 and March 1986. Prior to definite radiotherapy, patients were evaluated by physical examination and radiologic studies including chest, laryngogram and CT scan and then these patients were grouped according to the American Joint Committee (AJC) staging system. They were treated with RT alone or postoperative irradiation to the dose of 7,200 cGy/8 weeks and 6,000 cGy/7 weeks respectively. The results were obtained and as follows; 1. Overall male to female sex ratio was 3.6:1. The peak age of patients with head and neck cancer was 6th decade. 2. In all patients treated by RT, the ratio of squamous cell 1 carcinoma to non-squamous cell carcinoma was 3.5:1 (60/77 patients). 3. The incidence according to the anatomic site of primary tumor was 22 cases in the larynx, 12 cases in PNS, 7 cases in nasopharynx, 6 cases in oropharynx, and 3 cases in hypopharynx. 4. According to AJC staging system,4 cases were Stage 1,7 in Stage II, 19 in Stage III and 27 in Stage IV. 5. The overall incidence of cervical lymph node metastases was $43\%$ and subdigatric and submaxillary triangle lymph nodes were the most frequent site of metastases. 6. Local control was achieved in $48\%$ of patients treated by radio-therapy. 7. The lung was the most common site for distant metastases, comprising 4 cases among 7 cases in which distant metastases occured. 8. The overall estimated 5-year survival rate was $43\%$ in the head and neck cancer treated with radiotherapy by life-table analysis.

• Radiation Oncology Journal
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• v.20 no.2
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• pp.123-129
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• 2002

Purpose : The purpose of this study 띤as to determine the potential role of three-dimensional conformal radiotherapy (3D-CRT) in the treatment of primary unresectable hepatocellular carcinoma. The preliminary results on the efficacy and the toxicity of 3D-CRT are reported. Materials and Methods : Seventeen patients were enrolled in this study, which was conducted prospectively from January 1995 to June 1997. The exclusion criteria included the presence of extrahepatic metastasis, liver cirrhosis of Child-Pugh classification C, tumors occupying more than two thirds of the entire liver, and a performance status of more than 3 on the ECOG scale. Two patients were treated with radiotherapy only while the remaining 15 were treated with combined transcatheter arterial chemoembolization. Radiotherapy was given to the field including the tumor plus a 1.5 cm margin using a 3D-CRT technique. The radiation dose ranged from $36\~60\;Gy$ (median; 59.4 Gy). Tumor response was based on a radiological examination such as the CT scan, MR imaging, and hepatic artery angiography at $4\~8$ weeks following the completion of treatment. The acute and subacute toxicities were monitored. Results : An objective response was observed in 11 out of 17 patients, giving a response rate of $64.7\%$. The actuarial survival rate at 2 years was $21.2\%$ from the start of radiotherapy (median survival; 19 months). Six patients developed a distant metastasis consisting of a lung metastasis in 5 patients and bone metastasis in one. The complications related to 30-CRT were gastro-duodenitis $(\geq\;grade\;2)$ in 2 patients. There were no treatment related deaths and radiation induced hepatitis. Conclusion : The preliminary results show that 3D-CRT is a reliable and effective treatment modality for primary unresectable hepatocellular carcinoma compared to other conventional modalities. Further studies to evaluate the definitive role of the 3D-CRT technique in the treatment of primary unresectable hepatocellular carcinoma are needed.