• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.3
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• pp.843-854
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• 1991

본 연구에서는 제반 설계이론과 방법론을 적용하여 기존의 모델들이 가지고 있는 결점을 극복할 수 있는 독창적인 인공심장을 설계하고, 그 결과 시스템 설계에 있어서의 체계적인 설계방법론 적용의 타당성과 효율성을 입증하고자 한다. 또한 그 과정에서 인공장기 설계시에 만족시켜야 할 원칙을 제시하고, 그러한 원칙을 효과 적으로 만족시킬수 있는 새로운 설계원리를 탐구하고자 한다.

• Journal of Biomedical Engineering Research
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• v.8 no.2
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• pp.161-170
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• 1987

A new type of motor-driven total artificial heart system with a rolloing-cylinder mechanism has been developed. The prototype system consists of a brushless DC motor inside of a rolling-cylinder, two arc shaped pusher-plate s, and two ventricles of smooth, seamless polyurethane sacs. The motor-driven pump has the advantages of being portable and quiet compared to the present air-driven pump. It can also be controlled more accurately. This rolling-cylinder type electromechanical pump has several structural advantages including small size and weight, as compared to other research groups' motor-driven pumps. The results of mock circulation tests confirm sufficient pump output capacity(cardiac output . 9 L/min, at aortic pressure'120mmHg, with heart rate . 120 BPM) for animal implantation of our prototype system.

• Proceedings of the KOSOMBE Conference
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• v.1997 no.05
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• pp.51-54
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• 1997

Lumbrokinase, potent fibrinolytic enzyme purified from earthworm, was immobilized onto the total artificial heart valves using photoreaction. This valve were implanted into the lamb for three days. After experiments, thrombus was observed in the untreated valves whereas no thrombus was observed in the lumbrokinase immobilized valves. The fibrinolytic activity and proteolytic activity of the implanted valve was examined. The fibrinolytic activity of the valve was remained after the implantation. The lumbrokinase could be a suitable fibrinolytic agents in the vascular contacting devices to reduce the thrombus.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2410-2414
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• 2008

Human heart valves diseased by congenital heart defects, rheumatic fever, bacterial infection, cancer may cause stenosis or insufficiency in the valves. Treatment may be with medication but often involves valve repair or replacement (insertion of an artificial heart valve). Bileaflet mechanical heart valves (BMHVs) are widely implanted to replace the diseased heart valves, but still suffer from complications such as hemolysis, platelet activation, tissue overgrowth and device failure. These complications are closely related to both flow characteristics through the valves and leaflet dynamics. In this study, the physiological flow interacting with the moving leaflets in a bileaflet mechanical heart valve (BMHV) is simulated with a strongly coupled implicit fluid-structure interaction (FSI) method which is newly organized based on the Arbitrary-Lagrangian-Eulerian (ALE) approach and the dynamic mesh method (remeshing) in FLUENT. The simulated results are in good agreement with previous experimental studies. This study shows the applicability of the present FSI model to the complicated physics interacting between fluid flow and moving boundary.

• Proceedings of the KOSOMBE Conference
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• v.1997 no.05
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• pp.59-63
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• 1997

It is needless to say that the hemodynamic variables estimation is a very important study for the artificial heart. Even though its importance there have not been satisfactory results which can be applied to the real-world situations. This paper surveys and recommends how to cope with the problem of hemodynamic variable estimation for the moving-actuator type total artificial heart (MA-TAH).

• Proceedings of the KOSOMBE Conference
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• v.1996 no.11
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• pp.125-128
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• 1996

A new type of motor-driven total artificial heart system with a moving-actuator mechanism has been developed. The prototype system consists of a brushless do motor inside of actuator, two polyurethane sacs, and peripheral devices with internal controller. In this research work, the moving-actuator type electromechanical total artificial heart was redesigned for a good anatomical fitting. For total implantation we are developing the internal controller with high reliability and stability, and automatic control algorithm in response to the physiological requirements of animal. Contents and scope of the research work on ";Development of a totally implantable artificial heart of pre-clinical stage"; is summerized below 1) Animal experiment using sheep(55-60kg) 2) Development of implantable controller 3) Automatic control algorithm 4) Improvement of biocompatibility 5) Redesign of Actuator/blood pump.

• Journal of Cardiovascular Imaging
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• v.31 no.4
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• pp.207-208
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• 2023

• Korean Journal of Radiology
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• v.24 no.9
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• pp.849-859
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• 2023

Objective: The prognostic value of the volume and density of skeletal muscles in the abdominal waist of patients with colon cancer remains unclear. This study aimed to investigate the association between the automated computed tomography (CT)-based volume and density of the muscle in the abdominal waist and survival outcomes in patients with colon cancer. Materials and Methods: We retrospectively evaluated 474 patients with colon cancer who underwent surgery with curative intent between January 2010 and October 2017. Volumetric skeletal muscle index and muscular density were measured at the abdominal waist using artificial intelligence (AI)-based volumetric segmentation of body composition on preoperative pre-contrast CT images. Patients were grouped based on their skeletal muscle index (sarcopenia vs. not) and muscular density (myosteatosis vs. not) values and combinations (normal, sarcopenia alone, myosteatosis alone, and combined sarcopenia and myosteatosis). Postsurgical disease-free survival (DFS) and overall survival (OS) were analyzed using univariable and multivariable analyses, including multivariable Cox proportional hazard regression. Results: Univariable analysis showed that DFS and OS were significantly worse for the sarcopenia group than for the non-sarcopenia group (P = 0.044 and P = 0.003, respectively, by log-rank test) and for the myosteatosis group than for the non-myosteatosis group (P < 0.001 by log-rank test for all). In the multivariable analysis, the myosteatotic muscle type was associated with worse DFS (adjusted hazard ratio [aHR], 1.89 [95% confidence interval, 1.25-2.86]; P = 0.003) and OS (aHR, 1.90 [95% confidence interval, 1.84-3.04]; P = 0.008) than the normal muscle type. The combined muscle type showed worse OS than the normal muscle type (aHR, 1.95 [95% confidence interval, 1.08-3.54]; P = 0.027). Conclusion: Preoperative volumetric sarcopenia and myosteatosis, automatically assessed from pre-contrast CT scans using AI-based software, adversely affect survival outcomes in patients with colon cancer.

• Journal of Biomedical Engineering Research
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• v.15 no.4
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• pp.489-497
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• 1994

The most serious problems related to the cardiovascular prothesis are thrombosis and hemolysis. It is known that the flow pattern of cardiovascular prostheses is highly correlated with thrombosis and hemolysis. Laser Doppler Anemometry (LDA) is a usual method to get flow pattern, which is difficult to operate and has narrow measure region. Particle Image Velocimetry (PIV) can solve these problems. Because the flow speed of valve is too high to catch particles by CCD camera, high-speed camera (Hyspeed : Holland-Photonics) was used. The estimated maximum flow speed was 5m/sec and maximum trackable length is 0.5 cm, so the shutter speed was determined as 1000 frames per sec. Several image processing techniques (blurring, segmentation, morphology, etc) were used for the preprocessing. Particle tracking algorithm and 2-D interpolation technique which were necessary in making gridrized velocity pronto, were applied to this PIV program. By using Single-Pulse Multi-Frame particle tracking algorithm, some problems of PIV can be solved. To eliminate particles which penetrate the sheeted plane and to determine the direction of particle paths are these solving methods. 1-D relaxation fomula is modified to interpolate 2-D field. Parachute artificial heart valve which was developed by Seoul National University and Bjork-Shiely valve was testified. For each valve, different flow pattern, velocity profile, wall shear stress and mean velocity were obtained.

• Journal of Chest Surgery
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• v.17 no.3
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• pp.409-417
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• 1984

In the early days of open heart surgery, acute respiratory failure following extracorporeal circulation was a significant deterrent to an uncomplicated recovery. Although a marked improvement in prevention and treatment of postoperative respiratory failure has been achieved, the problem has not been completely eliminated and continues to be a causative factor in morbidity and mortality Fates following open heart surgery. We have attempted to evaluate postoperative respiratory failure in patients undergoing cardiac operation with the aid of extracorporeal circulation. Our series comprised 92 patients who underwent elective open heart surgery at the Department of Thoracic and Cariodvascular Surgery, School of Medicine, Kyungpook National University, from January, 1980 to December, 1982. In our study, the overall incidence of acute respiratory failure following open heart surgery was 18.8 percent. The duration of extracorporeal circulation in a series of 18 patients who developed postoperative respiratory failure [Group B] was longer in the mean value [120.3 minutes] than the uncomplicated 74 patients [Group A] [85.8 minutes]. The duration of artificial ventilation after open heart surgery in Group A averaged 13.4 hours as contrasted with 76.5 hours in Group B. In Group B, the inspired oxygen concentration [FiO2] in artificial ventilation was continued in the higher level than Group A until 18 hours after operation. Upon pulmonary function test performed pre-and postoperatively, residual volume[RV], RV/TLC and FEV 1.0/FVC were remained essentially unchanged following extracorporeal circulation, whereas forced vital capacity [FVC], FEV 1.0 and FEF 25-75% were significantly decreased in the early postoperative days. The incidence of acute respiratory failure was significantly higher in a series of patients who developed postoperative complications, such as re- exploration due to massive bleeding, low cardiac output, acute renal failure and arrhythmias. A total of 9 patients died, giving an overall mortality was 33.3 percent whereas the mortality was only 1.1 percent for patients without respiratory failure.