4D血流MR成像评估颅内动脉血流动力学状态的实验研究

目的旨在应用4D血流MR成像研究正常志愿者及大脑中动脉(MCA)狭窄病人的颅内动脉血流动力学状态,并比较正常和狭窄颅内动脉的双侧血流动力学参数差异。方法纳入正常志愿者5名和MCA狭窄病人3例。应用3 T MR设备进行检查,采用3D时间飞跃法(TOF)MRA及高分辨3D-T1WI-SPACE序列显示及分析Willis环结构特点。应用4D血流MR成像获取血流数据,分析双侧颈内动脉(ICA)颅内段、MCA及大脑前动脉(ACA)的血流动力学状态,计算心动周期不同时相的平均血管面积、平均及最大血流速度、平均瞬时血流率,生成血流矢量图、流线图及粒子追踪图。分析颅内Willis环的结构特征及血流动力学状态。采用独立样本t检验比较正常志愿者及MCA狭窄病人双侧动脉血流动力学参数的差异。结果正常志愿者中,4名显示对称Willis环结构,1名右侧胚胎型大脑后动脉。双侧ICA、MCA和ACA的血流动力学参数包括平均血管面积、平均血流速度、最大血流速度和平均瞬时血流率之间差异均无统计学意义(均P0.05)。血流矢量图、流线图及粒子追踪图显示,ICA可见高速血流,收缩晚期及舒张期显示血流速度下降,血流分布欠均匀。1名右侧胚胎型大脑后动脉志愿者双侧血流动力学参数明显不对称,除右侧ACA最大血流速度低于左侧,其余颅内血管段的平均血管面积、平均和最大血流速度以及平均瞬时血流率右侧均明显高于左侧。3例MCA狭窄病人的ICA、MCA及ACA双侧血流动力学参数之间的差异未见统计学意义(P0.05)。3例狭窄侧平均瞬时血流率均低于对侧。2例局部平均血流速度及相对压力梯度较对侧降低;另1例则明显较对侧增大。血流矢量图、流线图及粒子追踪图显示狭窄局部血流矢量明显偏离血管主轴方向,血流分布明显不规则。结论应用4D血流MR成像可以提供对颅内动脉复杂血流动力学状态的综合评估,包括对血流参数进行定量评价。颅内Willis环的结构与其血流动力学状态及分布密切相关。     

应用4D-FLOW MRI血流成像评价颅内囊状动脉瘤血流动力学状态特征

目的 应用四维血流磁共振成像(4D-FLOW MRI)技术,研究颅内囊状动脉瘤及瘤颈周围载瘤动脉内血流动力学变化特征。方法 经头颅CT血管造影(CTA)或磁共振血管造影(MRA)诊断为颅内囊状动脉瘤患者68例;应用4D-FLOW技术扫描并重建后进行血流动力学分析。在载瘤动脉的囊状动脉瘤入口截面处、囊状动脉瘤沿血流方向最大截面处、囊状动脉瘤出口截面处以及对侧动脉的对称位置分别手动勾画血管边缘轮廓,自动获取血流动力学参数。采用配对t检验比较载瘤动脉与对侧动脉之间的血流动力学参数。根据囊状动脉瘤最大径和尺寸比(SR)分组,采用独立样本t检验分析不同分组载瘤动脉血流动力学参数的差异。结果 载瘤动脉与对侧动脉比较,颅内囊状动脉瘤入口截面最大壁剪切应力(WSS)、平均WSS、最大轴向WSS-最大周向WSS小于对侧对称截面;囊状动脉瘤沿血流方向最大截面处最大WSS、平均WSS、平均轴向WSS、平均轴向WSS-平均周向WSS在载瘤动脉中较小,载瘤动脉中的最大能量损失和平均能量损失显著高于对侧动脉,上述差异均具有统计学意义(P<0.05)。在载瘤动脉中最大径>5 mm组的囊状动脉瘤入口截面最...     

超声向量血流成像在评估糖尿病患者颈动脉粥样硬化中的应用

目的 应用超声向量血流成像（V-Flow）技术观察糖尿病患者及正常人颈动脉壁剪切力（WSS）分布特征,定量分析不同动脉粥样硬化程度颈动脉WSS的差异。资料与方法 回顾性分析2019年4—6月在四川省人民医院确诊的糖尿病患者44例,对44例糖尿病患者（88支血管）和15例正常人（30支血管）进行常规颈动脉超声检查及V-Flow成像,根据颈动脉超声检查结果将糖尿病患者分为内-中膜厚度（IMT）正常组、IMT增厚组和斑块组;观察糖尿病患者与正常人颈动脉不同部位WSS的差异,并进一步分析糖尿病患者各组间WSS的变化特点。结果 本研究中糖尿病患者颈总动脉分叉处和中段WSS（包括WSS最大值和WSS平均值）均小于正常对照组颈总动脉对应部位WSS(P=0.001、0.003),同时正常对照组和糖尿病组颈总动脉分叉处WSS均明显小于颈总动脉中段,差异有统计学意义（P=0.001）。糖尿病患者中颈总动脉分叉处WSS的大小随动脉粥样硬化程度的增加而变化（P=0.018、0.043）,斑块组最高[WSS最大值（2.58±0.69）Pa;WSS平均值（0.86±0.25）Pa],IMT增厚组次之[（2.37±...     

MRI对急性Stanford B型主动脉夹层的形态及血液动力学的定量研究

目的 利用相位对比电影MRI(PC cine MRI)方法分析急性stanford B型主动脉夹层(AD)真腔和假腔内的血流特点及其与真腔塌陷程度的关系.方法 对11例急性Stanford B型AD患者进行真实稳态快速梯度回波(true FISP)、三维对比增强MR血管成像(3D CE MRA)、PC cine MRI检查,获得急性Stanford B型AD真腔和假腔内血流特点的定性、定量指标及真假腔的面积,真假腔血流速度、血流量及面积比较采用配对t检验,真腔塌陷程度与血流指标的相关性采用Pearson相关性分析.结果 胸主动脉(破口以远2 cm处)假腔平均面积为(8.10±2.93)cm2,真腔平均面积为(2.59±0.93)cm2,二者差异有统计学意义(t=-2.34,P＜0.05).假腔内平均血流速度[(2.81±0.73)cm/s]明显低于真腔[(15.52±2.84)cm/s],二者差异有统计学意义(t=-4.05,P＜0.01).真腔内平均血流量(36.32±5.37)ml,假腔内平均血流量(37.62±24.58)ml,差异无统计学意义(t=0.05,P＞0.05).腹主动脉肝门水平,真腔内平均血流速度[(10.46±5.57)cm/s]高于假腔内血流速度[(4.04±2.96)cm/s](t=-1.58,P＜0.05),该水平6例在收缩中晚期真假腔内血流方向相反,真腔内血流逆向,即真腔内为双向血流.真腔塌陷程度与假腔内血流速度和血流量密切相关(r分别为0.931和0.926,P值均＜0.01).结论 PC cine MRI能够定量测定AD真假腔的血流速度、血流模式,结合3D CE MRA可评价真腔塌陷程度,对AD的诊断、制定治疗方案和选择治疗时机具有重要的临床应用价值.     

后循环缺血的MR电影相位对比法血流定量研究

目的:探讨MR电影相位对比法测量后循环缺血患者双侧椎动脉血流流速、血流量等血流动力学参数的准确性及后循环缺血的原因。方法:28例经临床诊断为后循环缺血的患者及5例同年龄组健康志愿者,使用头部线圈和周围脉搏门控技术,采用MR电影相位对比法测量双侧椎动脉的血流动力学参数,并与经颅多普勒(TCDU)检查,结果进行比较,同时分析椎动脉血流量与血管狭窄程度的相关性。结果:MR电影相位对比和TCDU两种技术所测量的双侧椎动脉流速呈高度相关(左侧r=0.887,P=0.013;右侧r=0.785,P=0.027)。MR电影相位对比法测得病变组左右椎动脉平均流速分别为(16.16±7.99)和(15.72±9.92)cm/s,平均血流量分别为(66.63±45.23)和(68.57±38.84)ml/min。MR电影相位对比法所测血流量正常对照组与后循环缺血组之间差异有统计学意义。椎动脉血流量与血管狭窄程度无明显相关性(r=-0.144,P=0.654)。结论:使用MR电影相位对比法可无创性准确评价后循环缺血患者血流动力学改变,后循环的平均椎动脉血流量与血管狭窄程度低度相关。     

腹腔镜胆囊切除术前利用256层螺旋CT血管成像技术评估胆囊动脉

目的经过256层螺旋CT血管成像技术察看胆囊癌、胆囊炎时胆囊动脉显示状况、能否影响胆囊动脉起源,并测量胆囊动脉管径及横截面积。方法选取在我院行上腹增强扫描检查并提示胆囊癌、胆囊炎及胆囊未见异常患者的影像资料,观察并记录各组资料胆囊动脉显示率、显示评分、起源,并测量胆囊动脉直径及横截面积。结果胆囊炎组91例,胆囊动脉显示率96.7%(88/91),其中胆囊动脉起源变异13例(14.8%),88例患者中,显示评分1分19例、2分69例;胆囊癌30例,胆囊动脉显示率96.7%(29/30),其中胆囊动脉起源变异5例(17.2%),29例患者中,显示评分1分3例、2分26例;胆囊正常组100例,胆囊动脉显示率94.0%(94/100),其中胆囊动脉变异16例(17%),94例患者中,显示评分1分58例、2分36例。各组间进行统计分析,胆囊动脉显示率及起源变异无统计学意义(P0.05),胆囊动脉显示评分有统计学意义(P0.05);对各组胆囊动脉直径及横截面积的测量:胆囊炎症组98支,直径平均(1.99±0.39)mm,横截面积平均(3.30±1.25)mm2,胆囊癌组30支,直径平均(2.44±0.69)mm,横截面积平均(5.11±3.46)mm2,胆囊正常组101支,直径平均(1.78±0.30)mm,横截面积平均(2.59±0.83)mm2,各组间比较,有显著差异(P0.05)。结论胆囊合并胆囊炎及胆囊癌时256层螺旋CT可以很好的评估胆囊动脉,能够作为腹腔镜胆囊切除术的术前检查。     

iFlow软件量化评估下肢动脉阻塞性疾病血流改变的价值

目的 探讨iFlow软件量化评估下肢动脉阻塞性疾病介入治疗前后血流动力学改变的价值.方法 回顾性分析经CTA明确诊断,且行介入治疗成功的16例症状性外周动脉疾病患者.患者均分4段行下肢动脉血管造影,而后行狭窄闭塞部位的球囊扩张和(或)支架植入治疗.采用量化分析iFlow软件对血管造影数据进行分析.测量术前和术后即刻股总动脉分叉部、腘动脉分叉部和踝关节水平的达峰时间(TTP)值,并计算腘动脉分叉部TTP与股总动脉分叉部TTP的差值(腘动脉分叉部TTP差值)和踝关节水平TTP和股总动脉分叉部TTP的差值(踝关节水平TTP差值).采用t检验比较上述参数值的变化.结果 16例介入手术均顺利完成,未出现与介入操作相关的并发症.股总动脉分叉部术前TTP为(5.46±2.69)s,术后为(4.64±0.92)s,差异无统计学意义(t=-1.161,P＞0.05).腘动脉分叉部、踝关节水平术前TTP分别为(13.49±3.96)、(22.84±7.27)s,术后分别为(9.84±2.44)、(14.88±4.56)s,差异均有统计学意义(t值分别为-3.142和-3.710,P均＜0.01).腘动脉分叉部、踝关节水平术前 TTP差值分别为(8.03±4.04)、(17.38±6.17)s,术后分别为(5.20±2.42)、(10.25±4.64)s,差异均有统计学意义(t值分别为2.404和3.746,P均＜0.05).结论 通过iFlow软件量化分析评估下肢动脉阻塞性疾病血管成形术前后的血流动力学变化准确、可行.     

颈动脉狭窄:MR相位对比流动定量作为MRA的一种辅助方法的临床效用

由于MRA安全且准确度高,对颈动脉狭窄的监测有帮助。相位对比法MR流动定量能对所要求血管的任意部分无创性地测量容量流率和速度曲线。因此,可提供狭窄部位血流动力学的额外信息。作者对强内和颈总动脉的容量流率(VFR)和最大心脏收缩速率(RSV)做了测量。 研究对象为10例志愿者颈动脉Doppler US和MRA所见正常。疑颈动脉狭窄的55例病人行MR相位对比血流定量。由神经科医生连续提供的首批45例病人做了主动脉弓和颈动脉血管造影。在24小时内每例都做了DSA、MRA和Doppler US检查。     

基于影像学的管壁切应力在冠状动脉粥样硬化中的研究进展

管壁切应力(WSS)属于血流动力学因素,在冠状动脉粥样硬化的演变过程发挥着重要作用。综述WSS的基本概念及在冠状动脉粥样硬化斑块发生发展中的作用,并重点探究基于血管内成像技术、冠状动脉CT血管成像等影像学技术的WSS研究现状,以及相关血流动力学模型在预测斑块进展、破裂并评估血流动力学风险中的价值,以提高识别责任斑块的效能,为临床进一步诊疗提供重要帮助。     

非等势椎动脉MR血流定量测量

目的 探讨非等势椎动脉两侧血管血流量测量的意义.方法 对52例非等势椎动脉和30例等势椎动脉正常志愿者双侧椎动脉内血流进行MR相位对比电影法扫描,并通过流速分析软件测定流量.结果 等势椎动脉组右侧、左侧平均 血流量为(1.45±0.42) ml/s、(1.47±0.52) ml/s,平均峰值血流量为(2.18±0.69) ml/s、(2.24±0.74) ml/s.非等势椎动脉组优势侧、劣势侧平均血流量为(1.69±0.39) ml/s、(1.09±0.36) ml/s,平均峰值血流量为(2.92±0.85) ml/s、(1.81±0.77) ml/s.结论 非等势椎动脉血流量的测量对病变定位、定性具有重要的意义.     

Assessment of wall shear stress in the common carotid artery of healthy subjects using 3.0-tesla magnetic resonance

Background: Wall shear stress (WSS) has been proven to play a critical role in the formation and development of atherosclerotic plaques. Measurement of WSS in vivo is significant for the clinical assessment of atherosclerosis.

Purpose: To assess the magnitude and distribution of local WSS in the common carotid artery (CCA) in vivo using 3.0T magnetic resonance (MR).

Material and Methods: The common carotid artery of eight healthy volunteers was studied using a cine phase-contrast MR sequence. A three-dimensional paraboloid model was applied to fit the velocity profiles, and the WSS values were calculated. The cross-sectional area, average flow velocity, maximum velocity, and flow rate were also obtained.

Results: Mean WSS was 0.850±0.195 (range 0.132-3.464) N/m² for the common carotid arteries; the spatial and temporal distribution and change of WSS were displayed. During a cardiac cycle, the mean velocity was 22.8±3.5 (16.9-28.3) cm/s, blood flow rate 8.03±1.45 (5.73-10.72) ml/s, and luminal vessel area 34.94±7.06 (24.25-49.01) mm².

Conclusion: Local WSS values in CCAs can be measured using 3.0T MR imaging combined with image-processing techniques. Intersubject variations were found in the distribution and magnitude of wall shear stress as well as in the flow profile pattern in CCAs, which may be caused by different vessel morphologies.     

Reproducibility of wall shear stress assessment with the paraboloid method in the internal carotid artery with velocity encoded MRI in healthy young individuals

PURPOSE: To verify whether wall shear stress (WSS) can be assessed in a reproducible manner using automatic model-based segmentation of phase-contrast MR images by determination of flow volume and maximum flow velocity (Vmax) in cross-sections of these vessels. MATERIALS AND METHODS: The approach is based on fitting a 3D paraboloid to the actual velocity profiles and on determining Vmax. WSS was measured in the internal carotid arteries of two groups of healthy young volunteers. The reproducibility of rescanning and repositioning was studied in the first group. In the second group a 1-week and a 1-month interval was investigated. Reproducibility was calculated by the intraclass correlation (ICC). RESULTS: The flow volume, Vmax, and WSS averaged over the cardiac cycle were found to be 287.8 +/- 29.7 mL/min, 37.0 +/- 4.6 cm/s, and 1.13 +/- 0.16 Pa, respectively. The diastolic WSS varied between 1.00 +/- 0.21 Pa without averaging to 0.88 +/- 0.16 Pa with temporal and spatial averaging. Systolic WSS was 1.67 +/- 0.33 Pa without averaging and 1.67 +/- 0.25 Pa with averaging. ICC varied between 0.58 and 0.87 without averaging and between 0.75 and 0.90 with averaging for WSS. CONCLUSION: WSS in MR images of the internal carotid artery can be assessed semiautomatically with good to excellent reproducibility without inter- or intraobserver variability using model-based postprocessing.     

The influence of flow, vessel diameter, and non-newtonian blood viscosity on the wall shear stress in a carotid bifurcation model for unsteady flow

OBJECTIVES: The atherosclerotic process in arteries is correlated with the local wall shear stress (WSS). Plaque development particularly occurs in regions with recirculation (ie, where the WSS oscillates). We investigated the effects of non-Newtonian blood viscosity, variations in flow rate, and vessel diameter on wall phenomena in a carotid bifurcation model. MATERIALS AND METHODS: The flow through a model of a carotid artery bifurcation was simulated by means of the finite element method. The whole-blood viscosity is a function of shear rate, and was modeled by the Carreau-Yasuda (CY) model. Flow rate and vessel morphology were assessed with magnetic resonance imaging. Flow rate, blood viscosity, and hematocrit levels (Hct) were measured in 49 healthy volunteers. We propose an adaptation of the CY model so that differences in Hct can be incorporated; furthermore, plasma viscosity was varied in the CY model. RESULTS: The data from our model indicate that flow increases have a larger effect on the WSS than predicted with a simple paraboloid model. Hct had more influence on the WSS when the plasma viscosity was low. Low plasma viscosity was associated with a low WSS, which implies a contradiction, because both high WSS and low plasma viscosity are thought to be indicators for a healthy system. Maximum WSS oscillations were found at the edges of the recirculation region. CONCLUSIONS: Flow and diameter changes have significant influence on wall shear stress values; the same is true for the viscosity, but to a lesser extent.     

Determination of cerebral blood flow with a phase-contrast cine MR imaging technique: evaluation of normal subjects and patients with arteriovenous malformations.

This study evaluated a phase-contrast cine magnetic resonance (MR) imaging technique capable of simultaneously allowing determination of velocity and volume flow rate (VFR) in both carotid arteries and the basilar artery. Forty patients were studied; 24 were neurologically normal, and 16 had intracerebral arteriovenous malformations (AVMs). In the normal group, mean basilar flow was significantly less than mean carotid flow. Mean velocity and VFR showed a significant decline with age in the basilar artery. Carotid artery flow and total cerebral blood flow did not decline with age. In the AVM patients, flow and velocity measurements were significantly elevated in all three arteries. Flow in the carotid artery ipsilateral to the AVM was significantly greater than flow in the contralateral carotid artery. VFR increased in all three arteries with increasing AVM volume. Four patients underwent partial embolization, and a corresponding decrease in flow was observed. Phase-contrast cine MR imaging provides rapid, simultaneous, noninvasive velocity and VFR measurement in the major intracranial arteries.     

Preliminary study of hemodynamics in human carotid bifurcation by computational fluid dynamics combined with magnetic resonance angiography

Background: A longstanding hypothesis that correlates fluid dynamic forces and atherosclerotic disease has led to numerous analytical, numerical, and experimental studies over the years because it is very difficult to measure the hemodynamic variables of blood in vivo.

Purpose: To investigate the technique of visualization and quantitation of hemodynamic variables at carotid artery bifurcation in vivo by combining computational fluid dynamics (CFD) and vascular imaging.

Material and Methods: Twenty-six healthy volunteers underwent magnetic resonance (MR) angiography of the bilateral carotid artery by a 3.0T whole-body scanner. Hemodynamic variables at these carotid bifurcations were calculated and visualized by combining vascular imaging post-processing and CFD.

Results: The average velocity of the carotid bifurcation in the systolic phase and the diastolic phase was 0.46±0.24 m/s and 0.23±0.05 m/s, respectively. Eddy current and back flows were observed at bifurcation and the lateral part of the proximal internal carotid arteries (ICA) and external carotid arteries (ECA), and the shapes of them changed with phases of the cardiac cycle, which were significant at the middle of the systolic phase and faded out quickly downstream of the ICA and ECA. The average range of wall shear stress (WSS) at the bifurcation was 4.36±1.32 Pa, and the maximum WSS was 18.02±4.11 Pa. The WSS map revealed a large region of low WSS at the carotid bulb and extended to the outer wall in the proximal end of the ICA (the lowest value was below 0.5 Pa), and there was also a small region of low WSS at the outer wall in the proximal end of the ECA.

Conclusion: CFD combined with vascular imaging can calculate and visualize hemodynamic variables at carotid bifurcation in vivo individually.     

Measuring wall shear stress distribution in the carotid artery in an African population: Computational fluid dynamics versus ultrasound doppler velocimetry

IntroductionComputational fluid dynamics (CFD) and ultrasound Doppler velocimetry are diagnostic tools useful for determining carotid artery segments susceptible to atheromatous plaque development. This study computes and compares the difference in Wall Shear Stress (WSS) measurements between these two methods.MethodsThe carotid artery of 204 volunteers selected using simple random sampling were scanned using standard carotid doppler protocols. Four segments of the carotid artery – the common, internal, external carotid, and the carotid bulb were sonographically assessed. The intima-media thickness, diameter, peak systolic velocity, and end-diastolic velocity were measured at a point 2 cm away from the carotid bifurcation for the three segments, while the carotid bulb was measured at the bifurcation. A 2D incompressible Navier–Stokes Equation for modelling Newtonian, pulsatile, and laminar flow in a viscoelastic pipe was applied to model velocity flow across the carotid artery using COMSOL software. WSS values were computed for experimental and CFD measurements and the results were compared.ResultsThe WSS values generated by the model had respectively peak and average values of 19.81 N/cm² and 15.76 ± 1.81 N/cm² for the common carotid, 10.77 N/cm² and 7.57 ± 1.66 N/cm² for the internal carotid, 11.51 N/cm² and 8.05 ± 1.65 N/cm² for the external carotid, 37.55 N/cm² and 26.55 ± 6.62 N/cm² for the carotid bifurcation, 1.39 N/cm² and 3.13 ± 1.34 N/cm² for the carotid bulb. The model measurements matched doppler velocimetry measurements with <15% variation.ConclusionModel based WSS values were higher but comparable with doppler velocimetry measurements. The carotid bulb had low WSS and is therefore the segment highly disposed to atheromatous plaque formation.Implications for practiceSubject-specific mathematical models could be incorporated during cardiovascular scan work up for accurate WSS distribution and early prediction of possible atherosclerotic sites.     

Blood flow in the carotid arteries: quantification by using phase-sensitive MR imaging

The feasibility of MR phase-sensitive imaging for the quantification of blood flow in the carotid arteries was studied in two normal volunteers and six patients with carotid artery and/or cerebrovascular disease. The technique consists of sensitizing the phase of the MR signal to blood flow velocity gated to different times in the cardiac cycle. Flow velocities and volumes were measured by using transverse planes in the common, internal, and external carotid arteries, and flow curves were generated. Measurements made by using flow phantoms correlated well with calculated results. The MR measurements yielded values between 250 and 580 ml/min for the total flow through each of the common carotid arteries in the two normal volunteers. Markedly reduced flow (about 50% below normal) was detected in a patient whose arteriogram showed severe occlusion of the internal carotid artery. In a second patient, who had a large frontal intracranial arteriovenous malformation noted by arteriography, the MR-quantified flow was abnormally high (about 1 liter/min). In the remaining four patients, the findings on phase-sensitive quantification were consistent with those expected from clinical and other laboratory studies (including arteriography and sonography). These preliminary findings suggest that MR phase mapping may be a feasible tool for the noninvasive quantification of carotid blood flow.     

Blood flow in major cerebral arteries measured by phase-contrast cine MR.

PURPOSETo measure mean blood flow in individual cerebral arteries (carotid, basilar, anterior cerebral, middle cerebral, and posterior cerebral) using a cine phase contrast MR pulse sequence.METHODSTen healthy volunteers (22 to 38 years of age) were studied. The cine phase-contrast section was positioned perpendicular to the vessel of interest using oblique scanning planes. This pulse sequence used a velocity encoding range of 60 to 250 cm/sec. From the velocity and area measurements on the cine images, mean blood flow was calculated in milliliters per minute and milliliters per cardiac cycle. In the same subjects, transcranial Doppler measurements of blood velocity in these same vessels were also obtained.RESULTSThere was no difference in blood flow in the paired cerebral arteries. Carotid arteries had mean blood flow in the range of 4.8 +/- 0.4 ml/cycle, the basilar artery 2.4 +/- 0.2 ml/cycle, the middle cerebral artery 1.8 +/- 0.2 ml/cycle, the distal anterior cerebral artery 0.6 +/- 0.1 ml/cycle, and the posterior cerebral artery 0.8 +/- 0.1 ml/cycle. Overall, there was poor correlation between MR-measured and transcranial Doppler-measured peak velocity.CONCLUSIONAlthough careful attention to technical detail is required, mean blood flow measurements in individual cerebral vessels is feasible using a cine phase-contrast MR pulse sequence.     

流固耦合分析血液黏滞系数对重度狭窄颈动脉的影响

目的基于流固耦合(FSI)力学的方式,分析不同血液黏滞系数对重度狭窄颈动脉的血液流速及壁面剪切力(WSS)的影响。方法选取2015年8月于天津市第四中心医院经CT血管成像(CTA)检查诊断为颈内动脉重度狭窄(狭窄程度为75%)的1例62岁男性病人,将其CTA影像数据制作模型,导入FSI分析软件中,分别设定血液黏滞系数为1、3.5、6、8.5、11 c P并进行运算。在运算结果中测量并分析颈总动脉末端(A1)、颈动脉窦水平(A2)、颈内动脉狭窄处(A3)、颈内动脉狭窄处远端(A4)截面的血液流速和WSS值。结果随着血液黏滞系数的升高,A1、A2、A3、A4的血流速度均值降低,WSS均值增大;A4的中心血液流速降低,A1、A2和A3的中心血流速度升高。结论随着颈动脉重度狭窄病人的血液黏滞系数升高,其脑部供血不足趋于严重化,从而导致急性脑卒中的发生,而且造成狭窄位置斑块的破损概率和面积进一步增大,因此应引起临床的高度重视并及时干预。     

Reproducibility study of 3D geometrical reconstruction of the human carotid bifurcation from magnetic resonance images.

The combined magnetic resonance imaging (MRI) and computational fluid dynamics (CFD) modeling approach is playing an increasingly important role in advancing our understanding of the relationship between hemodynamics and arterial disease. Nevertheless, such a modeling approach involves a number of uncertainties associated with various stages of the process. The present study is concerned with the reproducibility of geometry reconstruction, one of the most crucial steps in the modeling process. The reproducibility test was conducted on the right carotid bifurcation of eight normal human subjects, each of whom were scanned twice using the same MR protocol with an in-plane resolution of 0.625 mm. Models constructed from different scans of the same subject were compared and assessed using four quantitative measures: centerline distance, cross-sectional area, contour shape factors, and mean radius difference. The difference in the maximum carotid bulb area between the two scans was found to be <8.1% for all subjects. Shape factors (measuring the dissimilarity between two contours) of <10% were achieved in most of the common carotid arteries (CCAs) and internal carotid arteries (ICAs). The mean radius difference between the two scans was <0.4 mm for all subjects. Among the three vessels, the geometry of CCA was well reproduced by the reconstruction procedure in most of the cases, while the external carotid artery (ECA) showed the worst reproducibility. The impact of geometrical differences on CFD-predicted flow patterns and wall shear stress (WSS) will be investigated and discussed in a separate paper.