Publications (13)21.79 Total impact
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Article: New Computerized Indices for Quantitative Evaluation of Depression and Asymmetry in Patients With Chest Wall Deformities.
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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; · 2.00 Impact Factor -
Article: A durability study of a paracorporeal pulsatile electro-mechanical pneumatic biventricular assist device.
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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. · 2.00 Impact Factor -
Article: In vivo evaluation of MMP sensitive high-molecular weight HA-based hydrogels for bone tissue engineering.
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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. · 2.63 Impact Factor -
Article: Fully automatic initialization method for quantitative assessment of chest-wall deformity in funnel chest patients.
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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. · 1.76 Impact Factor -
Article: Development of a closed air loop electropneumatic actuator for driving a pneumatic blood pump.
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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. · 2.00 Impact Factor -
Conference Proceeding: Bone regeneration using MMP sensitive-hyaluronic acid based hydrogels
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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 -
Article: Fluoroscopy-guided endovenous foam sclerotherapy using a microcatheter in varicose tributaries followed by endovenous laser treatment of incompetent saphenous veins: technical feasibility and early results.
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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. · 1.80 Impact Factor -
Article: Evaluation of tissue mimicking quality of tofu for biomedical ultrasound.
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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 alpha = 0.56 x f(1.3). 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 degrees C (equivalent to 3.18 J/g degrees C) of which about 76% is water. The nonlinear frequency dependence of attenuation in tofu as f(1.3) 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.Ultrasound in medicine & biology 01/2009; 35(3):472-81. · 2.02 Impact Factor -
Article: Endovenous laser ablation of the incompetent small saphenous vein with a 980-nm diode laser: our experience with 3 years follow-up.
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ABSTRACT: To demonstrate the long-term treatment outcomes of endovenous laser ablation (EVA) of incompetent small saphenous veins (SSV) with a 980-nm diode laser. Eighty-four patients (96 limbs), with varicose veins and reflux in the SSV on duplex ultrasound examination, were treated with a 980-nm diode laser under ultrasound- or fluoroscopy-guidance. Patients were evaluated at 1 week and 1, 3, 6 months, 1 year and yearly thereafter. In the 96 limbs, the technical success rate was 100%. The SSV remained closed in 89 of 93 limbs (96%) after 1 month, all of 82 limbs after 6 months, 77 limbs after 1 year, 71 limbs after 2 years and 55 limbs after 3 years. In four limbs where recanalisation was observed, repeat EVA was done resulting in successful obliteration of the SSV. No major complication occurred however bruising (27%), tightness or pain (13%) and paraesthesia (4.2%) were observed. Endovenous laser ablation with a 980-nm laser wavelength is an easy and safe procedure in incompetent SSVs. After successful treatment, there is a very low rate of recanalisation of the SSV, which suggests that the procedure will provide lasting results.European journal of vascular and endovascular surgery: the official journal of the European Society for Vascular Surgery 11/2008; 36(6):738-42. · 2.92 Impact Factor -
Article: Development of automatized new indices for radiological assessment of chest-wall deformity and its quantitative evaluation.
Med. Biol. Engineering and Computing. 01/2008; 46:815-823. -
Article: Non-contact sound speed measurement by optical probing of beam deflection due to sound wave.
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ABSTRACT: We report a non-contact and non-invasive method of sound speed measurement by optical probing of deflected laser beam due to normally incident degenerated shock wave. In this study the shock wave from an exploding wire was degenerated to an ordinary sound wave at the distance exceeding 0.23 m. Temporal resolution of the deflected beam signal was improved by passing through an adequate electronic high-pass filter, as a result we obtained a better temporal resolution than that of the acoustic pressure detection by PZT transducer in terms of rising time. The spatial resolution was improved by passing the refracted beam signal into the edge of focusing lens to make a larger deflection angle. Sound speed was calculated by monitoring the time of flight of transient deflected signal at the predetermined position. Sound speed has been measured in air, distilled water and acryl, agreed well with the published values. The sound speed measured in the solution of glycerin, magnesium sulfate (MgSO4), and dimethylformamide with various mole fractions also agrees within 3% of relative error with those measured in the present work by ultrasonic pulse echo method. The results suggest that the method proposed is to be reliable and reproducible.Ultrasonics 02/2006; 44(1):12-6. · 1.84 Impact Factor -
Article: Decrease of the electroacupuncture-induced analgesic effects in nuclear factor-kappa B1 knockout mice.
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ABSTRACT: To investigate the involvement of nuclear factor kappa B1 (NF-kappaB1; p50/p105) in electroacupuncture (EA)-induced analgesia, 2 and 100 Hz EA stimulations were applied at acupoint ST36 (Zusanli) in NF-kappaB1 knockout mice. EA was performed for 30 min and tail-flick latencies (TFLs) were evaluated every 15 min for 1 h. Wild-type mice displayed a 63.3% increase in TFLs compared to baseline after 2 Hz EA, whereas NF-kappaB1+/- mice exhibited a 41.8% increase and NF-kappaB1-/- mice showed only a 3.9% increase of TFLs. The TFLs of 100 Hz EA showed similar trends: a 72.6% increase of TFLs in wild-type, a 38.6% increase in NF-kappaB1+/- and a 9.3% increase in NF-kappaB1-/- mice. The present findings suggest that NF-kappaB1 may play a crucial role in both low and high frequency EA-induced analgesic effects.Neuroscience Letters 03/2002; 319(3):141-4. · 2.11 Impact Factor -
Article: Determination of accurate stent graft configuration in abdominal aortic aneurysm using computed tomography: a preliminary study.
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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 34(4):255-62. · 0.73 Impact Factor
Top co-authors
Top Journals
Institutions
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2009–2011
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Korea University
- Department of Biomedical Engineering
Seoul, Seoul, South Korea
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2010
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Korea Electrotechnology Research Institute-KERI
Pusan, Busan, South Korea
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2008
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Konkuk University
- Department of Radiology
Seoul, Seoul, South Korea
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2006
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Korea Research Institute of Standards and Science
Seoul, Seoul, South Korea
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