• Journal of Biomedical Engineering Research
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• v.19 no.2
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• pp.143-152
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• 1998

In this paper, we present the performances of a Doppler system using single channel RF(Radio Frequency) sampling. This technique consists of undersampling the ultrasonic blood backscattered RF signal on a single channel. Conventional undersampling method in Doppler imaging system have to use a minimum of two identical parallel demodulation channels to reconstruct the multigate analytic Doppler signal. However, this system suffers from hardware complexity and problem of unbalance(gain and phase) between the channels. In order to reduce these problems, we have realized a multigate pulsed Doppler system using undersampling on a single channel, It requires sampling frequency at $4f_o$(where $f_o$ is the center frequency of the transducer) and 12bits A/D converter. The proposed " single-Channel RF Sampling" method aims to decrease the required sampling frequency proportionally to $4f_o$/(2k+1). To show the influence of the factor k on the measurements, we have compared the velocity profiles obtained in vitro and in vivo for different intersequence delays time (k=0 to 10). We have used a 4MHz center frequency transducer and a Phantom Doppler system with a laminar stationary flow. The axial and volumetric velocity profiles in the vessel have been computed according to factor k and have been compared. The influence of the angle between the ultrasonic beam and the flow axis direction, and the fluid viscosity on the velocity profiles obtained for different values of k factor is presented. For experiment in vivo on the carotid, we have used a data acquisition system with a sampling frequency of 20MHz and a dynamic range of 12bits. We have compared the axial velocity profiles in systole and diastole phase obtained for single channel RF sampling factor.ng factor.

• Journal of Biomedical Engineering Research
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• v.24 no.4
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• pp.301-307
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• 2003

In this study, we Presented computational results on the blood flow in the sac of the Korean artificial heart. Two dimensional unsteady flow was assumed and we utilized a finite element commercial code ADINA to simulate the blood flow. Rigid body-solid contact were considered between the actuator and the blood sac and fluid-structure interaction between the blood and the sac. The three geometric models proposed in the design process were simulated to assess the hemodynamic characteristics of the models According to the computational results, a strong flow to the outlet and a stagnated flow region near the inlet were observed during systole. The sac was filled with blood and recirculating flow was generated near the outlet during diastole. Shear stress during systole had its extreme values near the outlet edge whereas the magnitude of shear stress values were relative)v high near the inlet edge and the contacting surface with the actuator.

• Journal of Korean Neurosurgical Society
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• v.62 no.2
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• pp.183-192
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• 2019

Objective : The objective of this study was to analyze patient-specific blood flow in ruptured aneurysms using obtained non-Newtonian viscosity and to observe associated hemodynamic features and morphological effects. Methods : Five patients with acute subarachnoid hemorrhage caused by ruptured posterior communicating artery aneurysms were included in the study. Patients' blood samples were measured immediately after enrollment. Computational fluid dynamics (CFD) was conducted to evaluate viscosity distributions and wall shear stress (WSS) distributions using a patient-specific geometric model and shear-thinning viscosity properties. Results : Substantial viscosity change was found at the dome of the aneurysms studied when applying non-Newtonian blood viscosity measured at peak-systole and end-diastole. The maximal WSS of the non-Newtonian model on an aneurysm at peak-systole was approximately 16% lower compared to Newtonian fluid, and most of the hemodynamic features of Newtonian flow at the aneurysms were higher, except for minimal WSS value. However, the differences between the Newtonian and non-Newtonian flow were not statistically significant. Rupture point of an aneurysm showed low WSS regardless of Newtonian or non-Newtonian CFD analyses. Conclusion : By using measured non-Newtonian viscosity and geometry on patient-specific CFD analysis, morphologic differences in hemodynamic features, such as changes in whole blood viscosity and WSS, were observed. Therefore, measured non-Newtonian viscosity might be possibly useful to obtain patient-specific hemodynamic and morphologic result.

• Korean Journal of Radiology
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• v.22 no.6
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• pp.901-911
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• 2021

Objective: To evaluate the technical applicability of a semiautomatic three-dimensional (3D) hybrid CT segmentation method for the quantification of right ventricular mass in patients with cardiovascular disease. Materials and Methods: Cardiac CT (270 cardiac phases) was used to quantify right ventricular mass using a semiautomatic 3D hybrid segmentation method in 195 patients with cardiovascular disease. Data from 270 cardiac phases were divided into subgroups based on the extent of the segmentation error (no error; ≤ 10% error; > 10% error [technical failure]), defined as discontinuous areas in the right ventricular myocardium. The reproducibility of the right ventricular mass quantification was assessed. In patients with no error or < 10% error, the right ventricular mass was compared and correlated between paired end-systolic and end-diastolic data. The error rate and right ventricular mass were compared based on right ventricular hypertrophy groups. Results: The quantification of right ventricular mass was technically applicable in 96.3% (260/270) of CT data, with no error in 54.4% (147/270) and ≤ 10% error in 41.9% (113/270) of cases. Technical failure was observed in 3.7% (10/270) of cases. The reproducibility of the quantification was high (intraclass correlation coefficient = 0.999, p < 0.001). The indexed mass was significantly greater at end-systole than at end-diastole (45.9 ± 22.1 g/m² vs. 39.7 ± 20.2 g/m², p < 0.001), and paired values were highly correlated (r = 0.96, p < 0.001). Fewer errors were observed in severe right ventricular hypertrophy and at the end-systolic phase. The indexed right ventricular mass was significantly higher in severe right ventricular hypertrophy (p < 0.02), except in the comparison of the end-diastolic data between no hypertrophy and mild hypertrophy groups (p > 0.1). Conclusion: CT quantification of right ventricular mass using a semiautomatic 3D hybrid segmentation is technically applicable with high reproducibility in most patients with cardiovascular disease.

• Journal of Veterinary Clinics
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• v.31 no.2
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• pp.85-89
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• 2014

Arterial thromboembolism (ATE) is a common and fatal complication of hypertrophic cardiomyopathy (HCM) in cats. Therefore in this study, we evaluated the hypercoagulability (using plasma concentration of D-dimer) in HCM cats with different stage of heart failure and left atrial enlargement and also investigated the any correlation with echocardiographic indices (including left free wall thickness at diastole, interventricular septal thickness at diastole, LA to Ao ratio, heart failure stage, existence of systolic anterior motion of mitral valve). The median plasma D-dimer concentration in this study population was $0.51{\pm}0.70$ (range 0 to 2.50) ug/mL in the control group, $1.47{\pm}1.29$ (range 0.3 to 5.79) ug/mL in the HCM group, $1.48{\pm}1.65$ (range 0.3 to 5.79) ug/mL in the ISACHC I group, $1.62{\pm}0.4$ (range 1.31 to 2.07) ug/mL in the ISACHC II group, $1.36{\pm}0.91$ (range 0.3 to 2.31) ug/mL in the ISACHC III group, $1.90{\pm}1.60$ (range 0.3 to 5.79) ug/mL in the cat with LA dilation, $1.72{\pm}0.72$ (range 0.6 to 2.31) ug/mL in cats with SEC-T, $1.19{\pm}0.70$ (range 0.3 to 2.31) ug/mL in the cats with SAM, and $1.63{\pm}0.80$ (range 0.6 to 2.31) ug/mL in the cats with ATE. Our study found the median and mean concentration of plasma D-dimer was higher in cat with HCM, ATE, SECT and SAM and clearly provides evidence of hypercoagulability in cats with HCM, although the severity was not correlated to the dilation of LA and the presence of heart failure. This is the first study evaluating the hypercoagulability in cats with HCM in Korea.

• Journal of Chest Surgery
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• v.35 no.1
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• pp.20-26
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• 2002

Background: Due to the concern of flow competition or retrograde steal, it has been generally suggested that the right gastroepiploic artery(RGEA) pedicled graft should be used in critical coronary stenosis lesion. The study was designed to evaluate the potential of retrograde flow competition in the RGEA pedicled graft by measuring the native pressure differences(PD) between the normal coronary artery and celiac arterial pressure, which would be compared with trans-stenosis pressure gradients(TSPG) in coronary artery occlusive disease. Material and Method: Between July, 1998 and February, 1999, pressures of the right coronary artery and the right gastroepiploic artery(or the celiac artery) were measured in patients with the patent right coronary artery(n=12). The PD between the arteries was compared with the TSPG in the occlusive coronary arteries(n=32). Result: The pressures of the normal right coronary artery and celiac artery were 143$\pm$23 vs. 134$\pm$17mmHg in systole(p<0.005), 74$\pm$13 vs. 73$\pm$14mmHg in diastole(p=NS), and 100$\pm$16 vs. 97$\pm$15mmHg in mean (p<0.05). The PD between the arteries were -8~25mmHg in systole, -4~7mmHg in diastole, and -1~10mmHg in mean. The TSPG measured in the occlusive coronary arteries were -4~19(7$\pm$5.8)mmHg in the lesion less than 75% stenosis vs. 7~74(27$\pm$18.3)mmHg in the 75% or over stenosis lesion(p<0.005). The normally existing pressure difference between the coronary arteries and RGEA(15~20mmHg) was significantlyless than the TSPG in .the occlusive coronary artery with 75% or over stenosis(p<0.001). Conclusion: If the pressure gradient between the RGEA and the coronary artery distal to the stenosis is the main determinant of development of retrograde flow competiton in the RGEA pedicled graft, the above data suggests that there will be little chance of competition when It is used in the coronary lesion with 75% or over stenosis.

• Journal of Life Science
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• v.22 no.2
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• pp.148-155
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• 2012

A cross-sectional analysis of blood pressure (BP) changes and the current prevalence and distribution of hypertension among age groups in Korea were conducted. Systolic (SBP), diastolic (DBP), and pulse (PP) pressures were evaluated. Residents visiting a local Community Health Center for a health check-up and/or participating in the Health Promotion Program were included for the analyses. A total of 6,570 subjects (2,809 men, 3,761 women) were divided into five age groups: 30-39, 40-49, 50-59, 60-69, and $70\leq$ years. Comparisons were made between sex and among age groups. SBP and DBP were continuously elevated, while men showed higher levels than women until their mid-60s; then, the trend was reversed. DBP in men became elevated from their 30s, reaching the highest in the 40s then slowly decreasing. DBP in women increased up to their 40s and 50s, then reached a plateau. PP increased rapidly from the 50s in both sexes. The major contributor of age-related BP elevation may be large artery stiffness in men, particularly from their 50s, while the blood pressure elevation of women may relate to diverse factors including large artery stiffness, stroke volume, and ventricular ejection rate. The rapid elevation of PP after the 50s in both men and women could represent a risk of cardiovascular or coronary mortality, particularly with increasing age. The current data showed a higher rate of hypertension in both sexes compared to previous reports. When those with both high-normal BP and hypertension are looked at in combination, BP management of the target population should be drastically elevated.

• Journal of Veterinary Clinics
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• v.32 no.5
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• pp.422-425
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• 2015

This study evaluated the myocardial performance on echocardiography after the sedation/anesthesia of medetomidine (D), the combination of medetomidine and tiletamine/zolazepam (DZ), and the combination of medetomidine, tiletamine/zolazepam and tramadol (DZT) in Beagle dogs. Ten healthy adult Beagle dogs (weighing $8.6{\pm}1.0kg$) were enrolled in this study. Heart rate (HR), fractional shortening (%FS), left ventricular ejection fraction (%LVEF), stroke volume (SV), cardiac output (CO), left ventricular internal diameter in systole (LVIDs) and left ventricular internal diameter in diastole (LVIDd) using M-mode echocardiography were measured prior to anesthesia, then every 10 min for 60 min. The HR, %FS, %LVEF, SV and CO were significantly decreased during sedation/anesthesia with D, DZ and DZT combination of anesthesia. Although those anesthetic protocols provided acceptable quality of sedation/anesthesia, levels of cardiovascular suppression were substantial and persistent and thus the continuous monitoring on vital signs should be accompanied in any situation. Close attention is required for dogs with pre-existing heart diseases, when those anesthetic protocols were applied.

• Journal of Biomedical Engineering Research
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• v.30 no.5
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• pp.401-411
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• 2009

In this paper, we correct pulse wave velocity(PWV) with heart-rate and derive regression equations to estimate intima-media thickness(IMT). Widely used methods for diagnosis of arteriosclerosis are IMT and PWV. Arterial wall stiffness determines the degree of energy absorbed by the elastic aorta and its recoil in diastole but there is not correlation between sclerosis and IMT in an existing study. In this study, we will correct PWV with heart-rate and get regression equation to estimate IMT using heart-rate correction index(HCI). We executed experiments for this study. Made up question of physical condition and measured electrocardiogram(ECG), photoplethysmogram (PPG) of finger-tip and toe-tip and ultrasound image of carotid artery. Calculated PWV and IMT using ECG, PPG and ultrasound image. We found that every p-value between PWV and IMT is not significant(<0.05). But p-value between IMT and HCI which is a corrected PWV using heart-rate is significant(>0.01). We use HCI and various measured parameter for estimating regression equation and apply backward estimation to select parameters for regression analysis. Result of backward estimation, found that only HCI is possible to derive proper regression equation of IMT. Relationship between PWV and IMT is the second order. Result of regression equation of E-H PWV is $R^2$=0.735, adj $R^2$=0.711. This is the best correlation value. We calculate error of its analysis for verification of earlobe PWV regression equation. Its result is RMSEP=0.0328, MAPE(%) = 4.7622. Like this regression analysis, we know that HCI is useful parameter and relationship between PWV, HCI and IMT. In addition, we are able to suggest possibility which is that we can get different parameter of prediction throughout just one measurement.

• Journal of Veterinary Clinics
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• v.32 no.1
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• pp.5-8
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• 2015

D-dimer is a fibrin degradation product (FDP), a small protein fragment present in the blood after a blood clot is degraded by fibrinolysis. D-dimer concentration is widely used for determining thrombosis and thromboembolism. Because one major cause of thromboembolism is congestive heart failure in human, we investigated the degree and risk of thromboembolism in dogs with different stage of congestive heart failure caused by chronic mitral valvular insufficiency (CMVI). The plasma level of d-dimer was evaluated in 20 healthy dogs and 30 dogs with different stage of congestive heart failure caused by CMVI. The d-dimer concentrations were measured by a commercialized assay kit. The plasma levels of d-dimer were not significantly different between healthy and CMVI dogs. Furthermore, there was no association of d-dimer concentrations to left atrium to aorta (LA/Ao) ratio, left ventricular dimension at diastole to aorta (LVIDd/Ao) ratio and severity of heart failure in our study population. Our study results implied that the degree of thromboembolism in canine heart failure might be minimal or the plasma d-dimer test might not be reliable for detecting thromboembolism in dogs.