국소 폐병변에서의 역동적 조용증강 CT의 유용성

신현준,최영철,전혜정,박정희,김요한 건국대학교 의과학연구소 1998 건국의과학학술지 Vol.8 No.-

The blood supply and metabolism of malignant nodules are qualitatively and quantitatively different from those of most benign nodules. We evaluated the efficacy of dynamic CT for differentiation of benign malignant lesions. Thirty-six patients with malignant nodule(n=20), tuberculoma(n=7), and pneumonic consolidation(n=9) were evaluated by thin section dynamic CT. CT numbers of lesion and aorta were measured before enhancement, and 1 minute, and 3 minutes after enhancement. Malignant lesions(maximum, 31.1±10.7 HU) enhanced significantly more than tuberculoma(maximum, 13.5±12.9 HU), but mass/aorta ratios were not so significantly different between malignant lesions(maximum, 0.61±0.27), tuberculoma(maximum, 0.36±0.15), and pneumonic consolidation(maximum,0.49±0.14). Dynamic CT is very useful for differentiation of malignant lesions from tuberculoma.

Theranostics and contrast agents for magnetic resonance imaging

Yohan Jeong,황희숙,나건 한국생체재료학회 2018 생체재료학회지 Vol.22 No.3

Background: Magnetic resonance imaging is one of the diagnostic tools that uses magnetic particles as contrast agents. It is noninvasive methodology which provides excellent spatial resolution. Although magnetic resonance imaging offers great temporal and spatial resolution and rapid in vivo images acquisition, it is less sensitive than other methodologies for small tissue lesions, molecular activity or cellular activities. Thus, there is a desire to develop contrast agents with higher efficiency. Contrast agents are known to shorten both T1 and T2. Gadolinium based contrast agents are examples of T1 agents and iron oxide contrast agents are examples of T2 agents. In order to develop high relaxivity agents, gadolinium or iron oxide-based contrast agents can be synthesized via conjugation with targeting ligands or functional moiety for specific interaction and achieve accumulation of contrast agents at disease sites. Main body: This review discusses the principles of magnetic resonance imaging and recent efforts focused on specificity of contrast agents on specific organs such as liver, blood, lymph nodes, atherosclerotic plaque, and tumor. Furthermore, we will discuss the combination of theranostic such as contrast agent and drug, contrast agent and thermal therapy, contrast agent and photodynamic therapy, and neutron capture therapy, which can provide for cancer diagnosis and therapeutics. Conclusion: These applications of magnetic resonance contrast agents demonstrate the usefulness of theranostic agents for diagnosis and treatment.

Synthesis of a gadolinium basedmacrocyclic MRI contrast agent for effective cancer diagnosis

Yohan Jeong,Kun Na 한국생체재료학회 2018 생체재료학회지 Vol.22 No.2

Background: Gadolinium-based contrast agents are widely used as a contrast agent for magnetic resonance imaging. Since gadolinium ions are toxic, many chelators are developed to bind gadolinium ions to prevent free gadolinium-associated disease. However, many reports indicated that linear chelator-based contrast agents are associated with nephrogenic systemic fibrosis (NSF) in patients with low kidney function. Therefore, the demand for stable macrocyclic chelator-based contrast agent is now increasing. Method: 1,4,7,10-Tetraazacyclododecane-1,4,7,10-tetraacetate (DOTA) was conjugated to lactobionic acid (LBA) through DCC-NHS coupling reaction. Gd3+ (gadolinium ion) was chelated to 1,4,7,10-Tetraazacyclododecane-1,4,7,10-tetraacetate-lactobionic acid (DOTA-LAE) and free Gd3+ was removed using a cation exchange column. In vitro cytotoxicity of contrast agent towards normal cells was measured using MTT assay. For in vivo MR imaging, contrast agents were intravenously injected to tumor-bearing mice and imaged by a MR imaging scanner. Results: This new macrocyclic gadolinium-based contrast agent showed enhanced in vitro paramagnetic properties compared to Gadovist. In addition, Gd-DOTA-LAE showed a 29% increased contrast enhancement of tumor tissue compared to normal tissue within 20 min past IV injection. Conclusions: We developed a new macrocyclic T1-weighted MR contrast agent. This new contrast agent offers various opportunities for cancer detection and diagnosis.

Biocompatible carbonized iodine-doped dots for contrast-enhanced CT imaging

Yohan Jeong,진민영,김경섭,나건 한국생체재료학회 2022 생체재료학회지 Vol.26 No.3

Background: Computed tomography (CT) imaging has been widely used for the diagnosis and surveillance of diseases. Although CT is attracting attention due to its reasonable price, short scan time, and excellent diagnostic ability, there are severe drawbacks of conventional CT contrast agents, such as low sensitivity, serious toxicity, and complicated synthesis process. Herein, we describe iodine-doped carbon dots (IDC) for enhancing the abilities of CT contrast agents. Method: IDC was synthesized by one-pot hydrothermal synthesis for 4 h at 180 ᕑ and analysis of its structure and size distribution with UV–Vis, XPS, FT-IR, NMR, TEM, and DLS. Furthermore, the CT values of IDC were calculated and compared with those of conventional CT contrast agents (Iohexol), and the in vitro and in vivo toxicities of IDC were determined to prove their safety. Results: IDC showed improved CT contrast enhancement compared to iohexol. The biocompatibility of the IDC was verified via cytotoxicity tests, hemolysis assays, chemical analysis, and histological analysis. The osmotic pressure of IDC was lower than that of iohexol, resulting in no dilution-induced contrast decrease in plasma. Conclusion: Based on these results, the remarkable CT contrast enhancement and biocompatibility of IDC can be used as an effective CT contrast agent for the diagnosis of various diseases compared with conventional CT contrast agents.

Evaluation of Transient Motion During Gadoxetic Acid–Enhanced Multiphasic Liver Magnetic Resonance Imaging Using Free-Breathing Golden-Angle Radial Sparse Parallel Magnetic Resonance Imaging

Yoon, Jeong Hee,Lee, Jeong Min,Yu, Mi Hye,Hur, Bo Yun,Grimm, Robert,Block, Kai Tobias,Chandarana, Hersh,Kiefer, Berthold,Son, Yohan Wolters Kluwer Health, Inc. All rights reserved. 2018 Investigative radiology Vol.53 No.1

<P>Objectives: The aims of this study were to observe the pattern of transient motion after gadoxetic acid administration including incidence, onset, and duration, and to evaluate the clinical feasibility of free-breathing gadoxetic acid-enhanced liver magnetic resonance imaging using golden-angle radial sparse parallel (GRASP) imaging with respiratory gating.& para;& para;Materials and Methods: In this institutional review board-approved prospective study, 59 patients who provided informed consents were analyzed. Free-breathing dynamic T1-weighted images (T1WIs) were obtained using GRASP at 3 T after a standard dose of gadoxetic acid (0.025 mmol/kg) administration at a rate of 1 mL/s, and development of transient motion was monitored, which is defined as a distinctive respiratory frequency alteration of the self-gating MR signals. Early arterial, late arterial, and portal venous phases retrospectively reconstructed with and without respiratory gating and with different temporal resolutions (nongated 13.3-second, gated 13.3-second, gated 6-second T1WI) were evaluated for image equality and motion artifacts. Diagnostic performance in detecting focal liver lesions was compared among the 3 data sets.& para;& para;Results: Transient motion (mean duration, 21.5 +/- 13.0 seconds) was observed in 40.0% (23/59) of patients, 73.9% (17/23) of which developed within 15 seconds after gadoxetic acid administration. On late arterial phase, motion artifacts were significantly reduced on gated 13.3-second and 6-second T1WI (3.64 +/- 0.34, 3.61 +/- 0.36, respectively), compared with nongated 13.3-second T1WI (3.12 +/- 0.51, P < 0.0001). Overall, image quality was the highest on gated 13.3-second T1WI (3.76 +/- 0.39) followed by gated 6-second and nongated 13.3-second T1WI (339 +/- 0.55, 2.57 +/- 0.57, P < 0.0001). Only gated 6-second T1WI showed significantly higher detection performance than nongated 13.3-second TIWI (figure of merit, 0.69 [0.63-0.76]) vs 0.60 [0.56-0.65], P = 0.004).& para;& para;Conclusions: Transient motion developed in 40% (23/59) of patients shortly after gadoxetic acid administration, and gated free-breathing T1WI using GRASP was able to consistently provide acceptable arterial phase imaging in patients who exhibited transient motion.</P>

Surface Texturing한 평행 스러스트 베어링의 열유체윤활 해석

정요한(YoHan Jeong),박태조(TaeJo Park) 한국트라이볼로지학회 2014 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.30 No.5

In order to reduce friction and improve reliability, researchers have applied various surface texturing methods to highly sliding machine elements such as mechanical seals and piston rings. Despite extensive theoretical research on surface texturing, previous numerical results are only applicable to isothermal and iso-viscous conditions. Because the lubricant flow pattern of textured bearing surfaces is much more complicated than that for non-textured bearings, the Navier?Stokes equation is more suitable than the Reynolds equation for the former. This study carries out a thermohydrodynamic (THD) lubrication analysis to investigate the lubrication characteristics of a single micro-dimpled parallel thrust bearing cell. The analysis involves using the continuity, Navier?Stokes, energy, temperature?viscosity relation, and heat conduction equations with the commercial computational fluid dynamics (CFD) code FLUENT. This study discretizes these equations using the finite volume method and solves them using the SIMPLE algorithm. The results include finding the streamlines, pressure and temperature distributions, and variations in the friction force and leakage for various dimple radii and depths. Increasing the dimple radius and decreasing the depth causes a recirculation flow to form because of a strong vortex, and the oil temperature greatly increases compared with the non-textured case. The present numerical scheme and results are applicable to THD analysis of various surface-textured sliding bearings and can lead to further study.

파라메트릭 설계법에 의한 파워보트 설계를 위한 연구

정요한(Yohan Jeong),유재훈(Jaehoon Yoo) 대한조선학회 2012 大韓造船學會 論文集 Vol.49 No.2

Impact of high body mass index on allograft outcomes in kidney transplant recipients with presensitization to human leukocyte antigen

( Yohan Park ),( Hanbi Lee ),( Eun Jeong Ko ),( Sua Lee ),( Tae Hyun Ban ),( Ji-won Min ),( Hye-eun Yoon ),( Eun-jee Oh ),( Chul Woo Yang ),( Byung Ha Chung ) 대한신장학회 2021 Kidney Research and Clinical Practice Vol.40 No.2

Background: This study aimed to investigate whether high body mass index (BMI) and presensitization to human leukocyte antigen (HLA) in kidney transplant recipients (KTRs) affected allograft outcomes. Methods: From January 2010 to December 2018, 1,290 kidney transplantations (KTs) were performed at the Seoul St Mary’s Hospital. Of these, 682 cases of ABO-compatible living donor KT patients were enrolled. They were divided into four groups (low BMI-non-sensitized, high BMI-non-sensitized, low BMI-sensitized, and high BMI-sensitized) according to the median BMI value (22.7 kg/m²) and HLA presensitization status (anti-HLA antibody mean fluorescence intensity > 3,000). Short-term and long-term allograft outcomes were compared between groups. Results: In the high BMI-sensitized group, the decline in allograft function was higher than that in the other three groups. Death-censored graft loss (DCGL) rates were highest in the high BMI-sensitized group (4 of 21 [19.0%], p = 0.04). In the multivariable Cox regression hazard regression model analysis, the hazard ratio (HR) for DCGL was intensified when high BMI and presensitization statuses were combined (HR, 3.75; p = 0.03); these statuses significantly interacted with each other (p-value for interaction = 0.008). Conclusion: Our results suggest that presensitization to HLA and high BMI might have an interactive adverse impact on allograft outcomes in KTRs.

Investigation of Rheological Properties of Succinoglycan Isolated from Sinorhizobium meliloti 1021 by NTG Mutagenesis and Variations of Culture Condition

Yohan KIM,Jeayul KIM,Jae-pil JEONG,Yiluo HU,Chunwoo LEE,Kyungho KIM,Seunho JUNG 한국생물공학회 2022 한국생물공학회 학술대회 Vol.2022 No.9

Mortality prediction of serum neutrophil gelatinase-associated lipocalin in patients requiring continuous renal replacement therapy

( Yohan Park ),( Tae Hyun Ban ),( Hyung Duk Kim ),( Eun Jeong Ko ),( Jongmin Lee ),( Seok Chan Kim ),( Cheol Whee Park ),( Chul Woo Yang ),( Yong-soo Kim ),( Byung Ha Chung ) 대한내과학회 2021 The Korean Journal of Internal Medicine Vol.36 No.2

Background/Aims: We investigated whether serum neutrophil gelatinase-associated lipocalin (NGAL) can predict mortality in patients with acute kidney injury (AKI) requiring continuous renal replacement therapy (CRRT). Methods: This study enrolled 169 patients who underwent serum NGAL testing at CRRT initiation from June 2017 to January 2019. The predictive power of serum NGAL level for 28-day mortality was compared to the Acute Physiology and Chronic Health Evaluation-II (APACHE-II) score and Sequential Organ Failure Assessment (SOFA) score via area under the receiver operating characteristic curve (AuROC) value. Results: There were 55 survivors and 114 non-survivors at 28 days post-CRRT initiation. Median serum NGAL level was significantly higher in the non-survivor group than in the survivor group (743.0 ng/mL vs. 504.0 ng/mL, p = 0.003). The AuROC value of serum NGAL level was 0.640, which was lower than APACHE-II score and SOFA score values (0.767 and 0.715, respectively). However, in the low APACHE-II score group (< 27.5), AuROC value of serum NGAL was significantly increased (0.698), and it was an independent risk factor for 28 day-mortality (hazard ratio, 2.405; 95% confidence interval, 1.209 to 4.783; p = 0.012). Conclusions: In patients with AKI requiring CRRT, serum NGAL levels may be useful for predicting short-term mortality in those with low APACHE-II scores.