Background: Pressure measurement in total cavopulmonary connection (TCPC) patients is a domain of cardiaccatheterization. 4D velocity encoded cardiovascular magnetic resonance (4D–flow MRI) offers an alternative fora...Background: Pressure measurement in total cavopulmonary connection (TCPC) patients is a domain of cardiaccatheterization. 4D velocity encoded cardiovascular magnetic resonance (4D–flow MRI) offers an alternative forassessment of even minor pressure differences. The scope of this study was to measure even minor pressure differencesin the anastomosis of TCPC patients, who are clinically uncompromised. Methods: Twenty-four patients(median 15 years [8;34]) with TCPC were studied prospectively by 4D-flow MRI. Pressure differences betweensuperior vena cava (SVC) and extracardiac conduit (C) to both right pulmonary artery (RPA) and left pulmonaryartery (LPA) were assessed. Small fluid obstructions as vortices within the anastomosis were detected by flowpathlines from 4D-flow MRI. In two patients pressure differences were calculated also by computational flowdynamics (CFD) as a plausibility check for the order of magnitude. Results: Median values of pressure differencesin the anastomosis between SVC and RPA were 0.63 (0.21–2.1) mmHg, between C and RPA 0.67 (0.3–2.2)mmHg, between SVC and LPA 0.8 (0.3–2.4) mmHg and between C and LPA 0.7 (0.2–1.9) mmHg. Patients withpotential flow obstruction (stents, occluder, vortices) had significantly higher gradients at the anastomosis (p <0.05) than patients without potential obstructions, although the absolute values were small. CFD- and measurement-based pressure difference showed good agreement. Conclusion: 4D-flow MRI is able to detect minor pressuredifferences within the Fontan circuit even in patients with apparently satisfactory TCPC. Slightly higherpressure differences are due to the presence of small flow obstruction.展开更多
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(...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P>0.05)。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(P>0.05)。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。展开更多
Under the demand of strategic air traffic flow management and the concept of trajectory based operations（TBO）,the network-wide 4D flight trajectories planning（N4DFTP） problem has been investigated with the purpose...Under the demand of strategic air traffic flow management and the concept of trajectory based operations（TBO）,the network-wide 4D flight trajectories planning（N4DFTP） problem has been investigated with the purpose of safely and efficiently allocating 4D trajectories（4DTs）（3D position and time） for all the flights in the whole airway network.Considering that the introduction of large-scale 4DTs inevitably increases the problem complexity,an efficient model for strategiclevel conflict management is developed in this paper.Specifically,a bi-objective N4 DFTP problem that aims to minimize both potential conflicts and the trajectory cost is formulated.In consideration of the large-scale,high-complexity,and multi-objective characteristics of the N4DFTP problem,a multi-objective multi-memetic algorithm（MOMMA） that incorporates an evolutionary global search framework together with three problem-specific local search operators is implemented.It is capable of rapidly and effectively allocating 4DTs via rerouting,target time controlling,and flight level changing.Additionally,to balance the ability of exploitation and exploration of the algorithm,a special hybridization scheme is adopted for the integration of local and global search.Empirical studies using real air traffic data in China with different network complexities show that the proposed MOMMA is effective to solve the N4 DFTP problem.The solutions achieved are competitive for elaborate decision support under a TBO environment.展开更多
基金This work was supported by Deutsche Herzstiftung e.V.
文摘Background: Pressure measurement in total cavopulmonary connection (TCPC) patients is a domain of cardiaccatheterization. 4D velocity encoded cardiovascular magnetic resonance (4D–flow MRI) offers an alternative forassessment of even minor pressure differences. The scope of this study was to measure even minor pressure differencesin the anastomosis of TCPC patients, who are clinically uncompromised. Methods: Twenty-four patients(median 15 years [8;34]) with TCPC were studied prospectively by 4D-flow MRI. Pressure differences betweensuperior vena cava (SVC) and extracardiac conduit (C) to both right pulmonary artery (RPA) and left pulmonaryartery (LPA) were assessed. Small fluid obstructions as vortices within the anastomosis were detected by flowpathlines from 4D-flow MRI. In two patients pressure differences were calculated also by computational flowdynamics (CFD) as a plausibility check for the order of magnitude. Results: Median values of pressure differencesin the anastomosis between SVC and RPA were 0.63 (0.21–2.1) mmHg, between C and RPA 0.67 (0.3–2.2)mmHg, between SVC and LPA 0.8 (0.3–2.4) mmHg and between C and LPA 0.7 (0.2–1.9) mmHg. Patients withpotential flow obstruction (stents, occluder, vortices) had significantly higher gradients at the anastomosis (p <0.05) than patients without potential obstructions, although the absolute values were small. CFD- and measurement-based pressure difference showed good agreement. Conclusion: 4D-flow MRI is able to detect minor pressuredifferences within the Fontan circuit even in patients with apparently satisfactory TCPC. Slightly higherpressure differences are due to the presence of small flow obstruction.
文摘目的基于4D Flow MRI技术探究急性心肌梗死患者左心室(left ventricular,LV)腔内局部血流动能(kinetic energy,KE)改变。方法纳入30名急性心肌梗死(acute myocardial infarction,AMI)患者和20名对照者。应用4D Flow MRI技术定量评价左心室腔内血流动能,包括左心室平均动能、最小动能、收缩期动能、舒张期动能以及平面内动能(in-plane kinetic energy,In-plane KE)百分比。比较心肌梗死组和对照组之间以及梗死节段与非梗死节段之间血流动能参数的差异。结果与对照组相比,急性心肌梗死组左心室整体平均动能(10.7μJ/mL±3.3 vs 14.7μJ/mL±3.6,P<0.001)、收缩期动能(14.6μJ/mL±5.1 vs 18.9μJ/mL±3.9,P=0.003)及舒张期动能(7.9μJ/mL±2.5 vs 10.6μJ/mL±3.8,P=0.018)均显著降低,其中梗死节段较非梗死节段邻近心腔血流的平均动能降低而收缩期平面内动能百分比增加(49.5μJ/mL±18.7 vs 126.3μJ/mL±50.7,P<0.001;61.8%±11.5 vs 42.9%±14.4,P=0.001)。结论4D Flow MRI技术可定量评价左心室腔内局部血流动能参数。急性心肌梗死后整体心腔血流动能减低,而梗死节段邻近心腔局部血流平面内动能百分比增加。
文摘目的旨在应用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P>0.05)。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(P>0.05)。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。
基金co-supported by the National Science Foundation for Young Scientists of China(No.61401011)the National Key Technologies R&D Program of China(No.2015BAG15B01)the Foundation for Innovative Research Groups of the National Natural Science Foundation of China(No.61521091)
文摘Under the demand of strategic air traffic flow management and the concept of trajectory based operations（TBO）,the network-wide 4D flight trajectories planning（N4DFTP） problem has been investigated with the purpose of safely and efficiently allocating 4D trajectories（4DTs）（3D position and time） for all the flights in the whole airway network.Considering that the introduction of large-scale 4DTs inevitably increases the problem complexity,an efficient model for strategiclevel conflict management is developed in this paper.Specifically,a bi-objective N4 DFTP problem that aims to minimize both potential conflicts and the trajectory cost is formulated.In consideration of the large-scale,high-complexity,and multi-objective characteristics of the N4DFTP problem,a multi-objective multi-memetic algorithm（MOMMA） that incorporates an evolutionary global search framework together with three problem-specific local search operators is implemented.It is capable of rapidly and effectively allocating 4DTs via rerouting,target time controlling,and flight level changing.Additionally,to balance the ability of exploitation and exploration of the algorithm,a special hybridization scheme is adopted for the integration of local and global search.Empirical studies using real air traffic data in China with different network complexities show that the proposed MOMMA is effective to solve the N4 DFTP problem.The solutions achieved are competitive for elaborate decision support under a TBO environment.
