• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 학술대회
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• pp.181-185
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• 2008

In this study, we attempted to quantify the relative importance of assumptions regarding blood rheology. Three patient-specific carotid bifurcation geometries and time-varying flow rates were obtained using magnetic resonance imaging. For each subject, CFD simulations were carried out assuming two different non-Newtonian rheology models Carreau and Ballyk models) and rescaled Newtonian viscosities based on characteristic shear rates to account for the shear-thinning property of blood. The sensitivity of WSS and oscillatory shear index (OSI) were contextualized with respect to the reproducibility of the reconstructed geometry and to assumptions regarding the inlet boundary conditions. We conclude that the assumption of Newtonian fluid is reasonable for studies aimed at quantifying the distribution of WSS-based extrema in an image-based CFD model of carotid bifurcation.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년 추계학술대회논문집
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• pp.181-185
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• 2008

In this study, we attempted to quantify the relative importance of assumptions regarding blood rheology. Three patient-specific carotid bifurcation geometries and time-varying flow rates were obtained using magnetic resonance imaging. For each subject, CFD simulations were carried out assuming two different non-Newtonian rheology models (Carreau and Ballyk models) and rescaled Newtonian viscosities based on characteristic shear rates to account for the shear-thinning property of blood. The sensitivity of WSS and oscillatory shear index (OSI) were contextualized with respect to the reproducibility of the reconstructed geometry and to assumptions regarding the inlet boundary conditions. We conclude that the assumption of Newtonian fluid is reasonable for studies aimed at quantifying the distribution of WSS-based extrema in an image-based CFD model of carotid bifurcation.

• Clinical and Experimental Reproductive Medicine
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• 제32권2호
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• pp.155-164
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• 2005

Objective: This study was performed to investigate the effects of pioglitazone, an insulin sensitizing agent, on insulin resistance, ovarian function and intraovarian stromal blood flow in patients with polycystic ovarian syndrome (PCOS). Material and Methods: Thirty patients with PCOS, aged 18~34 years, were recruited. Criteria for diagnosis of PCOS were as defined in 2003 Rotterdam consensus. They were treated for 6 months with pioglitazone at a dose of 30 mg/day orally. The hormonal blood profile, fasting serum glucose levels, a glycemic response to 75 g oral glucose tolerance test (OGTT), and an ovarian stromal artery (OSA) blood flow were assessed at baseline and after 6 months of treatment. Results: Eighteen (60.0%) of 30 patients treated with pioglitazone demonstrated a spontaneous ovulation After pioglitazone treatment, fasting insulin concentrations, serum glucose levels after 75 g OGTT significantly decreased (p=0.001, p=0.04, respectively), and fasting glucose to insulin (G/I) ratio significantly increased (p<0.001). The pioglitazone treatment induced a significant reduction in serum LH, testosterone (T) and free T levels (p<0.001, p=0.02, p=0.002, respectively). The resistance index (RI) values of OSA significantly increased after treatment (p<0.001). In analyzing pioglitazone-treated patients according to their body mass index (BMI), nonobese group as well as obese group showed a significant improvement in fasting G/I ratio (p<0.01). The pioglitazone treatment induced a significant reduction in serum LH and free T levels in nonobese group (p<0.001, p<0.05, respectively) as well as obese group (p=0.001, p<0.05, respectively). The RI values of OSA significantly increased in both nonobese and obese groups after pioglitazone treatment (p<0.001, p=0.003, respectively). Conclusions: Pioglitazone could ameliorate the glycoinsulinemic metabolism, and this beneficial effects of this drug could improve the endocrine-reproductive condition associated with the decrease of ovarian stromal artery blood flow, in both nonobese and obese patients with PCOS.

• The Korean Journal of Physiology and Pharmacology
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• 제4권3호
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• pp.253-261
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• 2000

Head-out water immersion induces marked increase in the cardiac stroke volume. The present study was undertaken to characterize the stroke volume change by analyzing the aortic blood flow and left ventricular systolic time intervals. Ten men rested on a siting position in the air and in the water at $34.5^{circ}C$ for 30 min each. Their stroke volume, heart rate, ventricular systolic time intervals, and aortic blood flow indices were assessed by impedance cardiography. During immersion, the stroke volume increased 56%, with a slight (4%) decrease in heart rate, thus cardiac output increased ${\sim}50%.$ The slight increase in R-R interval was due to an equivalent increase in the systolic and diastolic time intervals. The ventricular ejection time was 20% increased, and this was mainly due to a decrease in pre-ejection period (28%). The mean arterial pressure increased 5 mmHg, indicating that the cardiac afterload was slightly elevated by immersion. The left ventricular end-diastolic volume index increased 24%, indicating that the cardiac preload was markedly elevated during immersion. The mean velocity and the indices of peak velocity and peak acceleration of aortic blood flow were all increased by ${\sim}30%,$ indicating that the left ventricular contractile force was enhanced by immersion. These results suggest that the increase in stroke volume during immersion is characterized by an increase in ventricular ejection time and aortic blood flow velocity, which may be primarily attributed to the increased cardiac preload and the muscle length-dependent increase in myocardial contractile force.

• 대한의용생체공학회:의공학회지
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• 제23권4호
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• pp.281-286
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• 2002

심혈관계에서 자주 발생하는 죽상경화증과 혈전의 발생 및 성장에 관한 복잡한 기전을 이해하기 위하여 뇌의 혈액공급을 담당하는 경동맥을 2차원 축대칭으로 모사하여 수치해석하였다. 박동유동 상태에서 경동맥 내에 25%. 50%, 75%의 협착이 형성된 경우에 대하여 혈관내의 속도분포 및 혈류역학적 벽 파라미터들이 고찰되었다. 혈액은 뉴턴유체 및 전단변형률에 따라 점성이 변화하는 비뉴턴유체로 간주되었으며 비뉴턴모델로는 혈액과 유사한 점성치를 나타내는 Carraeu-Yasuda 모델이 적용되었다. 해석 결과 혈관내벽에 작용하는 벽전단응력은 협착이 커질수록 크게 증가하였으며 비뉴턴유체보다 뉴턴유체의 경우에서 벽전단응력이 크게 평가되었다. 벽전단응력 진동지표(OSI)에 의해 시간평균 재부착점이 예측되었는데 비뉴턴유체보다 뉴턴유체의 경우에서 협착 영역으로부터 멀리 떨어진 곳에서 관찰되었다. 시간평균 벽전단응력구배(WSSG)도 협착이 큰 경우에 상당히 크게 나타났는데 비뉴턴유체보다 뉴턴 유체의 경우에 더 큰 값이 나타났다.

• Journal of Korean Neurosurgical Society
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• 제39권1호
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• pp.20-25
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• 2006

Objective : The authors analyze prospectively the result of transcranial doppler[TCD] in normal pressure hydrocephalus and compared its cerebral blood flow parameters to radionuclide cerebrospinal fluid[CSF] flow study, postoperative brain computed tomography[CT] findings and clinical outcome, and studied the relationship between cerebral hemodynamics and clinical performance. Methods : Twenty five patients with hydrocephalus undertook pre- and post-operative TCD but only preoperative CSF flow study was performed. Mean flow velocity[Vm], pulsatility index[PI] and resistance index[RI] were assessed through TCD and changes in ventricle size and cortical gyral atrophy were checked through brain CT. Results : Postoperative hydrocephalus showed an increase in Vm[ACA P=0.037, MCA P=0.034], decrease in PI[ACA P=0.019, MCA P=0.017] and decrease in RI [ACA P=0.017, MCA P=0.021] compared to preoperative TCD parameters in the postoperative improvement group. In the postoperative improvement group, postoperative TCD parameters correlated with CSF flow study grade [Vm : $R^2=-0.75$, PI : $R^2=0.86$, RI : $R^2=0.78$] and ventriculocranial ratio change correlated with PI change [$R^2=0.73$]. The convexity gyral atrophy and initial TCD parameters showed close relationship to outcome. Conclusion : PI and RI can be used as an indicator of post operative prognosis, and with the addition of CSF flow study values, can also be used as a tool to predict pre-op and post-op patient status and successful shunt surgery.

• 한국방사선학회논문지
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• 제17권4호
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• pp.597-606
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• 2023

본 연구는 2022년 5월부터 2023년 2월까지 부산 지역 일개 의료기관을 내원한 환자들 중 경동맥 초음파 검사와 피검사를 모두 시행한 235명을 대상으로 후향적 분석을 시행하였다. 연구 목적은 경동맥 초음파를 통해 내중막 두께와 혈류속도를 측정하고 대상자들의 BMI 및 대사증후군 영향 인자들을 분석하여 내중막 두께와 혈류속도에 미치는 영향에 대하여 분석하고자 하였다. 경동맥 내중막 두께와 BMI의 상관관계 분석 결과 p=0.000으로 나타나 상관관계가 있는 것으로 확인되었다. 혈류속도와 BMI의 상관관계 분석 결과 p=0.015로 나타나 상관관계가 있는 것으로 확인되었다. 그밖에 연령(p=0.000), 공복혈당(p=0.002), 음주(p=0.006) 등이 경동맥 내중막 두께와 상관관계가 있는 것으로 나타났다. 경동맥 내중막 두께의 증가는 심뇌혈관질환으로 인한 이벤트의 증가를 발생시킨다. 따라서 경동맥 내중막 두께를 증가시키는 요인들을 배제 시키려는 노력이 반드시 필요하며 또한 다양한 예측 방법의 연구와 정기적인 검진을 통한 심혈관질환을 예방하는 것이 무엇보다 중요할 것이다.

• 한국조경학회:학술대회논문집
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• 한국조경학회 2007년도 Journal of Landscape Architecture in Asia Vol.3
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• pp.214-219
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• 2007

Psychological and physiological effects of plants were studied by investigating human responses while observing plants. Eighteen healthy adult male(aged between $19{\sim}25$ years) participated in this study. Semantic differential method(SD method) and multi-channel near-infrared spectroscopy(NIRS) were used to survey verbal and non-verbal response, respectively. Cerebral hemodynamics as a new evaluation index of brain activity was recorded for right brain hemisphere where visual information is mainly delivered. Thirty seconds of cerebral blood flow in forty seven channels were calculated when watching five types of picture images with different rates of hedge against gray block wall; 0:10, 3:7, 5:5, 7:3, 10:0. In the SD results, similar evaluations were found in all subjects. However, the change of cerebral hemodynamics as a non-verbal response varied among subjects. Largely two patterns of hemodynamics change were found with increasing plants rate in picture images; group A showed significant decreases of blood flow volume in many cortical regions, Group B had significant increase of blood flow volume in the occipital region for the scenes seen comparatively more plant. Our findings on the cerebral hemodynamics may indicate that there are two patterns of brain activity during observation of plants; group A in which brain areas associated with visual information and thinking work simultaneously to the visual stimuli; group B in which brain areas associated only with visual information work.

• 대한전기학회논문지:시스템및제어부문D
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• 제51권9호
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• pp.431-437
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• 2002

Low hemolysis is one of the key factors in the production of successful rotary blood pumps. It is, however, difficult to identify the areas where hemolysis occurs. Computational fluid dynamics(CFD) analysis enables the engineer to predict hemolysis on a computer Fluid dynamics in five different axial flow pumps was analyzed 3-dimensionally using CFD software. The impeller was rotated at a speed which supplied a flow of 5L/min at a pressure difference of 100mmHg. Changes in the turbulent kinetic energy along streamlines through the pumps were computed. Reynolds' shear stress( (equation omitted) ) was calculated using the turbulent kinetic energy. Hemolysis was evaluated based on Reynolds'shear stress and its exposure time(t) : dHb/Hb=3.62$\times$10$^{-5}$ $t^{0.785}$$\tau$$^{2.416}$ . Hemolysis of the pumps was measured in vitro using fresh bovine blood to which citrate phosphate dextrose was added to prevent clotting. A pump flow of 5L/min was maintained at a pressure difference of 100mmHg for 3h. The normalized index of hemolysis(NIH) as measured. Reynolds' shear stress was high behind the impellers. The measured NIH and the calculated hemolysis(dHb/Hb) shoed a good correlation; NIH=0.0003(dHb/Hb) (r=0.90, n=6) in the range of NIH between 0.003 and 1.1. CFD analysis can predict the in vitro results of hemolysis as well as the areas where hemolysis occurs.ysis occurs.

• Clinical and Experimental Pediatrics
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• 제46권10호
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• pp.983-988
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• 2003

목 적 : 실신은 소아에서 가장 흔한 증상이지만 기전은 잘 알려져 있지 않다. 증가된 미주신경의 활동과 감소된 교감신경의 자극이 저혈압, 서맥을 일으키고 마침내는 의식 소실을 초래한다. 이 연구의 목적은 혈관미주 신경성 실신으로 진단된 소아에서 기립경사 검사를 하는 동안 뇌 도플러 초음파를 실시하여 실신 전후의 뇌혈류 속도와 혈압, 심박동수 변화를 측정하고자 하였다. 방 법 : 실신의 과거력을 갖고 있는 64명의 소아를 대상으로 혈압을 10분간 안정 후와 15분 동안 기립 후에 측정하였고, 기립 경사 검사는 $80^{\circ}$에서 45분간 시행하였다. $80^{\circ}$ 각도의 경사 테이블에서 소아를 5분 간격으로 45분 동안 혈압, 심박동수, 산소 포화도를 측정하였다. 기립경사 검사를 하는 동안 실신이나 실신 전 증상이 나타난 소아에서는 검사를 중단하였다. 12-유도 심전도, 뇌파 검사, 심장 초음파를 시행하였다. 기립경사 검사에서 양성으로 나온 10명의 소아에서 Acouson 128XP/10 model 초음파 기기를 이용하여 중 대뇌동맥 혈류 속도, pulsatility 지수, time velocity integral, 혈압, 심박동수, 산소포화도 등을 측정하였다. 결 과 : 기립경사 검사에서 31.3%(20/64)의 양성률을 보였다. 검사 동안에 혈압과 맥박은 감소되지 않았고 뇌혈류 속도와 integral은 유의하게 감소되었다. 결 론: 뇌혈류 속도는 혈압이나 심박동수가 감소하기 전에 미리 감소하므로 실신 전 증상을 미리 예측할 수 있다. 뇌혈류의 자율 조절의 장애가 혈관미주 신경성 실신의 병인론에 중요한 역할을 하리라 생각된다.