• International Journal of Vascular Biomedical Engineering
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• v.1 no.2
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• pp.20-29
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• 2003

A new treatment for coronary artery occlusive disease is being developed in which a shunt or conduit is placed directly connecting the left ventricle with the diseased artery at a point distal to the obstruction. To aid in assessing and optimizing its benefit, a computational model of the cardiovascular system was developed and used to explore various design conditions. Simulation results indicate that in complete LAD occlusion, flow can be returned to approximately 65% of normal if the conduit resistance is equal for forward and reverse flow, increasing to 80% in the limit in which backflow resistance is infinite. Increases in flow rate produced by asymmetric flow resistance are considerably enhanced in the case of a partial LAD obstruction since the primary effect of resistance asymmetry is to prevent leakage back into the ventricle("steal") during diastole. Increased arterial compliance has little effect on net flow with a symmetric shunt, but leads to considerable augmentation when the resistance is asymmetric. These results suggest that an LV-LAD conduit will be beneficial when stenosis resistance(Rst) > 27 PRU if resistance is symmetric.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2935-2940
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• 2007

To diagnose circulatory diseases in the viewpoint of hemodynamics, we need to get quantitative hemodynamic information of blood flows related with the vascular diseases with high spatial resolution of tens micrometer and high temporal resolution in the order of millisecond. For investigating in-vivo hemodynamic phenomena, a new diagnosing technique combining medical radiography and PIV method was newly proposed and developed. This angiographic PIV technique consists of a medical X-ray tube, an X-ray CCD camera, a shutter module for double pulses of X-ray, and a synchronizer. The feasibility of the angiographic PIV technique was tested and quantitative flow velocity field distribution of a flow inside an opaque conduit was acquired by the developed system. It can be used for measuring flow phenomena of nontransparent fluids inside opaque conduits.

• Proceedings of the Optical Society of Korea Conference
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• 2009.02a
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• pp.427-428
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• 2009

Optical imaging offers excellent spatio-temporal sensitivity that is unparalleled by any other perfusion based imaging techniques. We used in vivo optical recording of intrinsic signals (ORIS) to map neurovascular hemodynamics of perfusion, oximetry and membrane potential during epileptic events in rat and mouse neocortex. Studies of hemodynamic changes with ORIS alone were also performed in human. Laboratory studies in rodent epilepsy models have demonstrated a persistent increase in deoxygenated hemoglobin (Hbr) and a decrease in tissue oxygenation during interictal spikes and ictal events. This "epileptic dip", like the "initial dip" recorded during normal sensory processing, implies that the enormous rise in cerebral blood flow (CBF) is inadequate to meet the increased metabolic demands associated with synchronized epileptic activity. These findings are critically important to the interpretation of the perfusion-based imaging studies, such as fMRI. In addition, we visualized the effect of direct cortical electrical stimulation, an alterative epilepsy treatment. The optical data following direct cortical electrical stimulation showed that hemodynamic signals are sensitive to different electrical stimulation parameters. Furthermore, our recent data demonstrated that the application of unilateral electrical stimulation is able to elicit bilateral hemodynamic responses in rat neocortex.

• 유체기계공업학회:학술대회논문집
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• 2002.12a
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• pp.489-492
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• 2002

The objective of the present study were to measure the viscosities of non-Newtonian fluids by the transient flow concept in a capillary tube and to apply to hemodynamic studies and pump performance evaluations. The developed capillary tube viscometer could be used to measure the viscosities of the non-Newtonian fluids for a wide range of the shear rate by a run of experiment in a very short time interval. The measured viscosities of water and blood fur different shear rates were good agreement with those of the well established data. The measured viscosities for muddy water varied with the shear rates.

• Annals of Clinical Neurophysiology
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• v.1 no.1
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• pp.39-46
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• 1999

Transcranial doppler ultrasonography (TCD) is a new, non-invasive and easily applicable method to evaluate cerebral hemodynamics. Last 10 years, its use in Korea has been dramatically expanded, but the qualification of TCD laboratory has yet to be settled. Since duplex sonography is seldom used in Korea, we have to depend totally on TCD to evaluate cerebral hemodynamic changes. Thus, all of the available data from every detectabler cerebral arteries has to be obtained for accurate interpretation of TCD measurements. Moreover, flow direction and wave form should be concerned in addition to the flow velocity. In this article, I present technique to measure the anterior, meddle and posterior cerebral arteries, the internal carotid artery siphon and at cervical level, and the vertebral and the basilar artery, and normal values for these measurements which is essential for the adequate interpretation.

• Annals of Clinical Neurophysiology
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• v.1 no.1
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• pp.47-54
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• 1999

The Doppler in neurosonologic examination could be applied to blood flow to determine its movement, the direction of its movement, and how fast it is. Indicies of the Doppler study denoted velocity, direction, and amount of RBC in the examined vessel. Systolic. diastolic, and mean blood flow velocities represent velocity of RBCs in a sample volume. Blood flow direction to the probe means direction of RBC to the probe. Size of amplitude displays toe amount of the RBCs passing the sample volume. Spectral broadening means presence of turbelence. The RBC movements and hemodynamics at the examined vessels can be estimated by analysis of Doppler indicies The formation and meaning of each of neurosonologic Doppler study is described in the present review.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.257-261
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• 2005

Over the past 30 years, numerical methods and simulation tools for fluid dynamic problems have advanced as a new discipline, namely, computational fluid dynamics (CFD). Although a wide spectrum of flow regimes are encountered in many areas of science and engineering, simulation of compressible flow has been the major driver for developing computational algorithms and tools. This Is probably due to a large demand for predicting the aerodynamic performance characteristics of flight vehicles, such as commercial, military, and space vehicles. As flow analysis is required to be more accurate and computationally efficient for both commercial and mission-oriented applications (such as those encountered in meteorology, aerospace vehicle development, general fluid engineering and biofluid analysis) CFD tools for engineering become increasingly important for predicting safety, performance and cost. This paper presents the author's perspective on the maturity of CFD, especially from an aerospace engineering point of view.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.124-127
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• 2002

Ceil embolisation technique has been used to treat the intracranial aneurysms. Microcoils inserted into the aneurysm sac induce the blood flow stagnation inside the aneurysm sac, which causes the thrombus formation and embolisation of aneurysm. Since the intraaneurysmal flow patterns affect the embolisation process, we want to measure the flow field for different locations of coil inside the aneurysm sac . Lateral aneurysm models are manufactured using rapid prototyping, and the velocity fields are measured using particle image velocitimeter. Distally blocked models showed less flow into the aneurysm sac comparing to proximally blocked models. Also blocking the neck of aneurysm showed better inflow blocking comparing to blocking the dome of aneurysm. These results suggest that distal neck should be the preferred locations of coil for aneurysm embolisation.

• Journal of Chest Surgery
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• v.17 no.1
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• pp.59-66
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• 1984

After open heart surgery, the patient must be carefully observed and adequately managed for his survival. This report reviewed 10 cases of ventricular septal defect and 12 mitral valvular diseases as hemodynamics early after open heart surgery. For postoperative 24 hours, clinical status was evaluated for left atrial pressure, central venous pressure,DP[LAP-CVP], peak systolic pressure, heart rate, urine amount, and other clinical findings. Especially, on postoperative fourth hour, cardiac output was most decreased, when the changes of monitoring were compared with two groups with or without using cardiotonics. Finally, we concluded as followings; 1.Postoperatively, variation of CVP was noted in VSD, but mitral valvular disease was more variable change of LAP. 2.DP was 1.3\ulcorner.4 cmH2O in VSD, and 6.4\ulcorner.2 cmH2O in mitral valvular disease. 3.Parameter using cardiotonic was CVP in VSD, and LAP in mitral valvular disease.

• The Journal of the Society of Korean Medicine Diagnostics
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• v.15 no.2
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• pp.159-168
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• 2011

Objectives: The purpose of this study is to develop the pulse wave analysis model with the palpation pressure and the skin effect. Methods: The position of pulse diagnosis was modeled with elastic string system. The skin was modeled with the elastic string, the palpation pressure with tension in the string, and the blood vessel pressure with external force on the string. Using the wave equation in the physics, the simplified pulse model was transformed to the mathematical model. Results: To the verification of the model, the effects of the palpation pressure and the skin effect were tested. Conclusions: There was optimal palpation pressure, describing the exact vessel pressure pattern and maximizing the amplitude of the skin displacement. For the optimal condition, the increased palpation pressure was needed with the increased skin thickness. Therefore, the developed pulse wave analysis model showed the good results.