Ho Chul Kim

Eulji University, Sŏngnam, Gyeonggi Province, South Korea

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Publications (31)31.6 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Stents are promising medical devices widely used in the prevention of cerebral aneurysm rupture. As the performance of stents depends on their mechanical properties and cell configuration, the aim of this study was to optimize the stent design and test the hemodynamic properties by using computational solid mechanics and computational fluid dynamics. In order to test their performance, computer-based cerebral aneurysm models that mimic the conditions present after implantation into the human brain were tested. The strut configuration selected was the closed-cell type, and nitinol was chosen as the material for stent manufacture because the innate characteristics of this material increase stent flexibility. Three ideal sample stent types with different cell configurations were manufactured. Computational solid mechanics analysis of the sample stents showed over 30% difference in flexibility between stents. Furthermore, using a cerebral aneurysm model simulation, we found that the stents eased the hemodynamic factors of the cerebral aneurysm and lessened the flow velocity influx into the sac. A decrease in flow velocity led to a 50-60% reduction in wall shear stress, which is expected to prevent aneurysm rupture under clinical conditions. Stent design optimization was carried out by simulation and electropolishing. Corrosion resistance and surface roughness were evaluated after electropolishing performed under variable conditions, but 40 V and 10 s were the most optimal.
    Artificial Organs 09/2015; DOI:10.1111/aor.12564 · 2.05 Impact Factor
  • Ho Chul Kim · Wonsik Jung · Kwonhee Lee · Ki Chang Nam
    06/2015; 16(6):4021-4030. DOI:10.5762/KAIS.2015.16.6.4021
  • Hyun Keun Jeong · Hyun Do Jeong · Ho Chul Kim
    02/2015; 52(2):182-192. DOI:10.5573/ieie.2015.52.2.182
  • 12/2014; 51(12):180-188. DOI:10.5573/ieie.2014.51.12.180
  • Sung Sun Noh · Hyo Sik Um · Ho Chul Kim
    12/2014; 51(12):163-173. DOI:10.5573/ieie.2014.51.12.163
  • Source
    Sun Suk Hong · Ho Chul Kim
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    ABSTRACT: The purpose is a comparative evaluation in the DR System according to the dosimetry and image quality of the quantitative and objective via Direct digital radiography, Indirect digital radiography, Image intensifier (Charge Coupled Device type) digital radiography. The experimental method used rando phantom and measured the entrance surface dose. And through using the measured entrance surface dose and then using the PCXMC program were evaluated risk due to irradiation and the effective dose. SNR and NPS and CNR were measured and analyzed by using 21cm acryl phantom. Significance of measured value was evaluated by statistics method. Entrance surface dose, major organ dose, effective dose all of them were measured the lowest rated in direct DR when it is on the basis of direct DR dose, high-dose ratio were measured in I.I DR approximately 1.3 times, indirect DR approximately 2.4 times. Risk in accordance with radiation also was measured same as dose ratio. On the conclusion that SNR measurement result based on direct DR SNR measurements, low-SNR ratio were measured in I.I DR approximately 7.25 times, indirect DR approximately 1.48 times. On the conclusion that CNR measurement result based on direct DR CNR measurements, high-dose ratio were measured in I.I type DR approximately 1.16 tims and low-dose ratio were measured in indirect DR approximately 0.87 times. Therefore Direct DR system using a-selenium sensing element to detect x-ray photon is thought effectively at the examination such as infant to sensitive irradiation and the genital gland. Because quality image is built by low dose. Also when it is necessary that image test requiring many diagnosis information, indirect DR system is thought effectively.
    12/2013; 50(12). DOI:10.5573/ieek.2013.50.12.247
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    ABSTRACT: An evaluation index that can quantitatively assess the severity of chest wall deformities is essential to prepare and assess corrective surgical operations for patients with these deformities, including funnel chest patients. In previous studies, our group proposed several automatically calculated indices that represent the severity of depression and asymmetry in the chest wall. These indices showed sufficient performance in most cases of deformities, including those involving asymmetric and symmetric depression; however, their linearity declined when assessing complex deformities. The purpose of this study is to propose two automated indices that provide linear evaluation output for all types of chest wall deformities, including complex deformities, and to evaluate their performance and clinical feasibility. Six reference chest wall boundary curves were obtained from 60 computed tomography (CT) images of a normal chest. Next, an active contour model-based image processing technique was used to extract boundary curves from images of patients with real chest wall deformities. Third, the required parameters were extracted from the boundary curves and the targeted indices were calculated. Finally, the performance of the proposed indices was evaluated using 33 synthetic images and 60 real chest CT images of patients with chest wall deformities. The newly proposed indices can be automatically calculated from the original CT images and showed sufficient performance for all types of chest wall deformities. We believe that the newly proposed indices can facilitate pre- and postoperative evaluation of chest wall deformities in clinical practice.
    Artificial Organs 05/2013; 37(8). DOI:10.1111/aor.12085 · 2.05 Impact Factor
  • Applied Mechanics and Materials 12/2011; 145:219-223. DOI:10.4028/www.scientific.net/AMM.145.219 · 0.15 Impact Factor
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    ABSTRACT: In 2002, the paracorporeal pulsatile electro-mechanical pneumatic ventricular assist device (VAD) began to be developed by the Korea Artificial Organ Center at Korea University under a Health & Medical Technology Research and Development program which finished in 2008. In vitro durability testing was conducted on the paracorporeal pulsatile pneumatic VAD to determine device durability and to evaluate device failures. The 1- and 2-year reliability of the paracorporeal pulsatile pneumatic VAD was shown to be 91.2% and 54.9%, respectively, with an 80% confidence level. Failure modes were analyzed using fault tree analysis, with customized software continuously acquiring data during the test period. After this period, 21 in vivo animal tests were done, with 14 cases of left atrium to left ventricle (LV) inflow cannulation (36Fr)/outflow grafting to descending aorta, and seven cases of apex cannulation of LV to descending aorta (12 mm). The longest postoperative day (182 days) in Korea was recently recorded in in vivo animal testing (bovine, 90 kg, male, 3.5-4.0 L/min flow rate, and 55 bpm).
    Artificial Organs 06/2011; 35(6):614-24. DOI:10.1111/j.1525-1594.2010.01187.x · 2.05 Impact Factor
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    ABSTRACT: multimodal biometric systems have been widely used to overcome the limitation of unimodal biometric systems and to achieve high recognition accuracy. However, users feel inconvenience because most of the multimodal systems require several steps in order to acquire multimodal biometric data, which also requires the specific behaviors of users. In this research, we propose a new multimodal biometric recognition of touched fingerprint and finger-vein. This paper is novel in the following four ways. First, we can get a fingerprint and a finger-vein image at the same time by the proposed device, which acquires the fingerprint and finger-vein images from the first and second knuckles of finger, respectively. Second, the device's size is so small that we can adopt it on a mobile device, easily. Third, fingerprint recognition is done based on the minutia points of ridge area and finger-vein recognition is performed based on local binary pattern (LBP) with appearance information of finger area. Fourth, based on decision level fusion, we combined two results of fingerprint and finger-vein recognition. Experimental results confirmed the efficiency and usefulness of the proposed method.
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    ABSTRACT: Hyaluronic acid (170 kDa)-based hydrogel was synthesized using acrylated hyaluronic acid (HA) and matrix metalloproteinase (MMP) sensitive HA-based hydrogels were then prepared by conjugation with two different peptides: cell adhesion peptides containing integrin-binding domains (Arg-Gly-Asp: RGD) and a cross-linker with MMP degradable peptides to mimic the remodeling characteristics of natural extracellular matrices by cell-derived MMPs. Mechanical properties of these hydrogels were evaluated with different weight percentages (2.5 and 3.5 wt %) by measuring elastic modulus, viscous modulus, and swelling ratio. Human mesenchymal stem cells (hMSCs) were then cultured in MMP-sensitive or insensitive HA-based hydrogels and/or immobilized cell adhesive RGD peptides in vitro. Actin staining and image analysis proved that cells cultured in the MMP-sensitive hydrogel with RGD peptides showed extensive cell spreading and sprouting. Gene expression analysis showed that bone specific genes such as alkaline phosphatase, osteocalcin, and osteopontin increased in MMP-sensitive hydrogels as biomolecules such as BMPs and cells were added in the gels. For in vivo calvarial defect regeneration, five different samples (MMP insensitive hydrogel, MMP sensitive hydrogel, MMP sensitive hydrogel with BMP-2, MMP sensitive hydrogel with hMSC, and MMP sensitive hydrogel with BMP-2 and hMSC) were prepared. After 4 weeks of implantation, the Masson-Trichrome staining and micro computed tomography scan results demonstrated that the MMP sensitive hydrogels with BMP-2 and hMSCs have the highest mature bone formation. The MMP sensitive HA-based hydrogel could become useful scaffolds in bone tissue engineering with improvements on tissue remodeling rates and regeneration activity.
    Journal of Biomedical Materials Research Part A 12/2010; 95(3):673-81. DOI:10.1002/jbm.a.32884 · 3.37 Impact Factor
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    ABSTRACT: An aortic stent graft is frequently used to cure an abdominal aortic aneurysm (AAA). It is critical to accurately fit the size and shape of the stent graft to the target region on the aorta. Proper sizing and shaping require the measurement of the orthogonal diameter of the target region from medical images. The present study aimed to acquire an accurate three-dimensional (3D) reconstruction of the aorta to determine the shape of the cross-sectional area where the stent graft would be implanted. A conventional geometric-active contour model was enhanced to prevent blurring and to improve edge detection with high noise resistivity. After the segmentation of two-dimensional (2D) images using the model, a 3D-reconstructed configuration of the aorta was achieved using a surface-rendering technique. The model could segment several selected synthetic images more accurately than conventional methods. Also, a 3D-reconstructed configuration of the abdominal aorta could be achieved using boundary coordinates extracted from 2D image segmentation. This preliminary study indicates the utility of the approach in optimizing stent graft configuration for AAA patients, thus enhancing stent graft healing.
    Clinical imaging 07/2010; 34(4):255-62. DOI:10.1016/j.clinimag.2009.06.023 · 0.81 Impact Factor
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    ABSTRACT: In our previous study, we developed a computerized technique that measured degree of chest-wall deformity in funnel chest patients using several image processing techniques, such as, active contour model. It could calculate quantitative indices for chest-wall deformity using patient's CT image. However, the algorithm contained manual initialization processes that required clinicians to obtain additional training processes to understand engineering contents and be familiar with the technique. In this study, we suggested a fully automatic algorithm that can measure the degree of chest-wall deformity by automating initialization processes. The initialization processes to segment CT images were automated by applying various image processing techniques such as histogram analysis, point detection, and object recognition. In order to evaluate the performance of the proposed algorithm, both the previous algorithm (semi-automatic) and newly suggested algorithm (fully automatic) were applied to preoperative CT images of 61 funnel chest patients to calculate several indices that represented chest-wall deformity quantitatively and to measure their processing time of our algorithm using a computer. The time required for initialization processes was 28.12 s using the semi-automatic algorithm and 0.07 s using the fully automatic algorithm (99.75% speed enhancement) and the time required for whole index calculation process was 61.12 s in semi-automatic algorithm and 30.09 s in fully automatic algorithm (50.76% speed enhancement). In most indices, calculation results of the two algorithms showed no significant difference between each other. The proposed algorithm could calculate chest-wall deformity more accurately with relatively shorter processing time than our previous method. Applying this algorithm is expected to facilitate more efficient diagnosis and evaluation processes of funnel chest patients for clinical doctors.
    Medical & Biological Engineering 06/2010; 48(6):589-95. DOI:10.1007/s11517-010-0612-3 · 1.73 Impact Factor
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    ABSTRACT: Our goal was to investigate the effects of low intensity resistance training on body fat, muscle mass and strength, cardiovascular fitness, and insulin sensitivity in type 2 diabetes. Twenty-eight overweight women with type 2 diabetes were randomly assigned to a resistance training group (RG, n = 13) or a control group (CG, n = 15). RG performed resistance training using elastic bands, of which strength was equal to 40 to 50% of one repetition maximum (1RM), for three days per week. Each exercise consisted of three sets for 60 minutes. We assessed abdominal fat using computed tomography, muscle mass using dual-energy X-ray absorptiometry, and muscle strength using Keiser's chest and leg press. Insulin sensitivity was measured using the insulin tolerance test, and aerobic capacity was expressed as oxygen uptake at the anaerobic threshold (AT-VO(2)) before and after the 12-week exercise program. The age of participants was 56.4 +/- 7.1 years, duration of diabetes was 5.9 +/- 5.5 years, and BMI was 27.4 +/- 2.5 kg/m(2), without significant differences between two groups. During intervention, a greater increase in muscle mass and greater decreases in both total fat mass and abdominal fat were observed in RG compared to those of CG (P = 0.015, P = 0.011, P = 0.010, respectively). Increase in 1RM of upper and lower extremities was observed in the RG (P = 0.004, P = 0.040, respectively), without changes in AT-VO(2) and insulin resistance in either group. In conclusion, the low intensity resistance training was effective in increasing muscle mass and strength and reducing total fat mass without change of insulin sensitivity in type 2 diabetic patients.
    Korean Diabetes Journal 04/2010; 34(2):101-10. DOI:10.4093/kdj.2010.34.2.101
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    ABSTRACT: Aerobic exercise can effectively reduce visceral fat. However, few studies have examined the effect of daily physical activity on obesity and cardiopulmonary function in the subjects with diabetes. We examined the effect of moderate intensity of walking in obese diabetes patients by monitoring of daily activity and measuring the change in abdominal fat area, muscle are and maximal muscle strength. We randomly assigned 27 obese women with type 2 diabetes to an aerobic exercise group (AG, n = 13) and control group (CG, n = 14). The AG performed moderate intensity walking for 60 minutes per exercise, 5 times per week, and for 12 weeks. The activity energy expenditure was monitored by a multi-record accelerometer. The CG maintained routine daily activities. At the time of the initiation of the study and after 12 weeks of exercise, the aerobic exercise capacity was assessed using oxygen consumption rate at anaerobic threshold (VO(2)-AT). The abdominal fat area and the quadriceps muscle area were measured by computed tomography, and the maximum muscle strength of the upper and lower limbs was measured by a chest press and a leg press, respectively. The mean age of the study subjects was 56.6 +/- 8.0 years, the mean duration of diabetes was 6.3 +/- 6.0 years, and the body weight index (BMI) was 27.3 +/- 2.7 kg/m(2). The BMI of the AG was significantly decreased (P = 0.003). In the AG, the visceral fat area and subcutaneous fat area were also significantly decreased (P = 0.018 and P < 0.001, respectively) but not in CG. VO(2)-AT of the AG was significantly improved, while that of the CG did not change (P = 0.009 and P = 0.115, respectively). The quadriceps muscle mass and the maximal muscle strength of the AG did not change, however, the CG showed a significant decrease. Duration of moderate intensity exercise was correlated with the decrease in total abdominal fat area (r = -0.484; P = 0.011) and that of high intensity exercise was correlated with improvement of cardiopulmonary function (r = 0.414; P = 0.032). Daily moderate intensity aerobic exercise is effective at reducing abdominal fat mass, while high intensity exercise improves cardiopulmonary function.
    Korean Diabetes Journal 02/2010; 34(1):23-31. DOI:10.4093/kdj.2010.34.1.23
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    ABSTRACT: In this study, we developed a small pneumatic actuator that can be used as an extracorporeal biventricular assist device. It incorporated a bellows-transforming mechanism to generate blood-pumping pressure. The cylindrical unit is 88 +/- 0.1 mm high, has a diameter of 150 +/- 0.1 mm, and weighs 2.4 +/- 0.01 kg. In vitro, maximal outflow at the highest pumping rate (PR) exceeded 8 L/min when two 55 mL blood sacs were used under an afterload pressure of 100 mm Hg. At a pumping rate of 100 beats per minute (bpm), maximal hydraulic efficiency was 9.34% when the unit supported a single ventricle and 13.8% when it supported both ventricles. Moreover, pneumatic efficiencies of the actuator were 17.3% and 33.1% for LVAD and BVAD applications, respectively. The energy equivalent pressure was 62.78 approximately 208.10 mm Hg at a PR of 60 approximately 100 bpm, and the maximal value of dP/dt during systole was 1269 mm Hg/s at a PR of 60 bpm and 979 mm Hg/s at a PR of 100 bpm. When the unit was applied to 15 calves, it stably pumped 3 approximately 4 L/min of blood at 60 bpm, and no mechanical malfunction was experienced over 125 days of operation. We conclude that the presently developed pneumatic actuator can be utilized as an extracorporeal biventricular assist device.
    Artificial Organs 07/2009; 33(8):657-62. DOI:10.1111/j.1525-1594.2009.00783.x · 2.05 Impact Factor
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    ABSTRACT: Hyaluronic acid (170 kDa)-based hydrogel was synthesized using acrylated hyaluronic acid. Matrix metalloproteinase (MMP) sensitive hyaluronic acid-based hydrogels were prepared by conjugation with two different peptides: cell adhesion peptides containing integrin binding domains (Arg-Gly-Asp: RGD) and a cross-linker with MMP degradable peptides to mimic the remodeling characteristics of natural extracellular matrices (ECMs) by cell-derived MMPs. Mechanical properties of these hydrogels were evaluated with different weight percent (2.5%wt and 3.5%wt) by measuring elastic modulus, viscous modulus and swelling ratio. Human mesenchymal stem cells (hMSCs) were cultured in MMP-sensitive or insensitive hyaluronic acid-based hydrogels and/or immobilized cell adhesive RGD peptides in vitro. Actin staining and image analysis proved that cells cultured in the MMP-sensitive hydrogel with RGD peptides showed dramatic cell spreading and sprouting. For in vivo calvarial defect regeneration, 3 different samples (MMP insensitive hydrogel, MMP sensitive hydrogel, MMP sensitive hydrogel with BMP-2 and hMSC) were prepared. After a 4-week implantation, the Masson-Trichrome (MT) staining and micro CT scan results demonstrated that the MMP sensitive hydrogels with BMP-2 and hMSCs had the highest mature bone formation. This MMP sensitive-hyaluronic acid based hydrogel could be useful in tissue engineering by improving tissue defect regeneration and tissue remodeling.
    Bioengineering Conference, 2009 IEEE 35th Annual Northeast; 05/2009
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    ABSTRACT: To evaluate the technical feasibility and preliminary results of endovenous foam sclerotherapy using a microcatheter in varicose tributaries followed by endovenous laser treatment (EVLT) of incompetent saphenous veins. From July 2005 to August 2006, 312 patients (M:F=139:173, mean age 45.8) who presented with varicose veins with reflux in the saphenofemoral, saphenopopliteal junction or tributaries were enrolled. Under ultrasound or fluoroscopy guidance, selective microcatheterization and endovenous foam slcerotherapy were first performed in varicose tributaries, followed by EVLT (980 nm) of incompetent saphenous veins. Follow-up at 1-week and 1-, 3-, and 6-month intervals was done. Technical success was seen in 410 of 411 limbs (99%). Continued closure of the saphenous veins and the complete sclerosis of varicose tributaries were noted in 332 of 373 limbs (89%) at the 1-month follow-up, all 307 limbs (100%) at the 3-month follow-up, and all 274 limbs (100%) at the 6-month follow-up. No serious complication was noted. Endovenous foam sclerotherapy using a microcatheter in varicose tributaries followed by EVLT in incompetent saphenous veins is a safe, effective, and technically feasible treatment for varicose veins. It not only reduces additional sclerotherapy and technical failure, but also makes multiple therapeutic sessions unnecessary.
    Dermatologic Surgery 04/2009; 35(5):804-12. DOI:10.1111/j.1524-4725.2009.01136.x · 2.11 Impact Factor
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    ABSTRACT: The tissue mimicking quality of tofu has been evaluated in terms of acoustic properties and acousto/thermal conversion as functions of frequency and diffraction corrected intensity over the 2 MHz to 18 MHz range using three unfocussed transducers with center frequencies of 5 MHz, 10 MHz and 15 MHz. The density and acoustic velocity were close to the American Institute of Ultrasound in Medicine (AIUM) recommended values for the soft tissue, however, the attenuation increases nonlinearly with frequency as α = 0.56 × f1.3. As a result, the temperature rise in tofu due to ultrasound absorption is expressed by the product of the acousto/thermal conversion factor and the attenuation/diffraction corrected acoustic intensity. The decrease of temperature rise with depth measured by embedded thermocouples agrees with the theoretical exponential decrease of the attenuation/diffraction corrected acoustic intensity. The heat capacity per unit mass of tofu is 0.76 cal/g°C (equivalent to 3.18 J/g°C) of which about 76% is water. The nonlinear frequency dependence of attenuation in tofu as f1.3 correctly describes the frequency dependence of temperature rise. The present results suggest that tofu may only be used in a limited low MHz range in view of the estimation of temperature rise and penetration depth due to nonlinear frequency dependence of attenuation. (E-mail: [email protected] /* */).
    Ultrasound in medicine & biology 03/2009; 35(3):472-81. DOI:10.1016/j.ultrasmedbio.2008.09.005 · 2.21 Impact Factor
  • Yong-Bong Lee · Ho Chul Kim · Seung-Woo Kim
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    ABSTRACT: We propose a simple method to estimate phase lags of the sensitivity of an accelerometer via primary vibration calibration. The method adopts the same homodyne interferometer as used in other primary calibration methods, e.g. a sine-approximation method, but uses a different signal-processing scheme. Assuming that the accelerometer is under sinusoidal excitation, we have Fourier transformed the interference signal from the photodetector directly. The interference signal in the frequency domain can be expanded into a series of infinite harmonic components with orders of n (n = −∞,...0,..., +∞), where each phase is an integer (n) multiple of a principal phase. We have derived a technique to find the principal phase from several harmonic components using the least-squares method. Experimental results showed good agreement with those of other methods, thus verifying that the proposed approach is reasonable. Given its simplicity and efficiency, the proposed method has the potential to be adopted as an alternative method for estimation of the phase lag of the accelerometer.
    Measurement Science and Technology 02/2008; 19(4):045204. DOI:10.1088/0957-0233/19/4/045204 · 1.43 Impact Factor

Publication Stats

114 Citations
31.60 Total Impact Points


  • 2013
    • Eulji University
      Sŏngnam, Gyeonggi Province, South Korea
  • 2010
    • Korea Electrotechnology Research Institute-KERI
      Tsau-liang-hai, Busan, South Korea
  • 2009–2010
    • Korea University
      • College of Medicine
      Sŏul, Seoul, South Korea
  • 1999–2009
    • Korea Advanced Institute of Science and Technology
      • Department of Physics
      Sŏul, Seoul, South Korea
    • Andong National University
      • Department of Physics
      Antō, Gyeongsangbuk-do, South Korea
  • 2000
    • Sun Moon University
      Onyang, South Chungcheong, South Korea