MR相位速度图及心导管检查对肺动脉血液动力学的对比研究

目的通过测量肺动脉瓣返流（PR）、分析PR的峰值流速和计算肺动脉舒张压（PADP）,评价MR相位速度图检测肺动脉血液动力学的价值。方法应用MR相位速度图测量了45例患者的主肺动脉直径、流速及其最大返流速度并与右心导管检查进行了比较,通过直线相关与回归分析判断MR相位速度图测量PADP的准确性和特异性。结果45例患者中40例存在返流,MR相位速度图测定的PADP为(4.82±1.24)mmHg（1mmHg=0.133kPa）,右心导管的测值为（4.52±2.00）mmHg,二者间的相关性系数r=0.94(P＜0.01),回归方程y=0.82x+4.58。其敏感性和特异性达90%。25例肺动脉高压（PAH）组主肺动脉的流速及肺血管的顺应性均低于非PAH组而返流的百分比显著性增高（P＜0.05）,返流量与肺动脉平均压呈正相关（r=0.89,P＜0.01）,与肺动脉峰值流速呈负相关（r=-0.82,P＜0.01）。结论MR相位速度图是评价肺动脉血液动力学变化的一种非创伤性新技术,能较准确地评价PR患者的PADP。     

MRI对肺动脉栓塞血液动力学评价的初步研究

目的 探讨MRI评价急性大面积肺动脉栓塞(简称肺栓塞)肺动脉血液动力学改变及肺动脉压力的价值.方法 21例经对比剂增强MR肺动脉造影(CE-MRPA)诊断的急性大面积肺栓塞患者和20名健康志愿者,获得MR血流编码肺动脉血流图像,测量主肺动脉直径、右肺动脉直径、主肺动脉血流峰值流速、平均流速、流量、反流在主肺动脉短轴平面的位置以及收缩期射血加速时间等血液动力学参数,比较肺栓塞患者与健康志愿者间肺动脉血液动力学参数的差异,并与右心导管检查对比,分析各血液动力学参数与肺动脉平均压的相关性.结果 急性大面积肺栓塞患者组与健康志愿者组的主肺动脉直径(分别为2.93、2.52 cm)、右肺动脉直径(分别为2.49、1.92 cm)差异有非常显著性意义(t值分别为3.55、4.19,P值均<0.01);患者组和健康志愿者组主肺动脉峰值流速(分别为85.29、100.63 cm/s)、平均流速(分别为11.00、17.12 cm/s)、流量(分别为89.15、98.96 ml/s)、收缩期射血加速时间(分别为105.09、163.85 ms)比较差异有非常显著性意义(t值分别为2.89、6.37、2.21、9.46,P值分别为0.01、<0.01、0.03、<0.01);急性大面积肺栓塞患者MR血流编码的肺动脉峰值流速-时间曲线表现为收缩期峰值流速降低且时间提前,并可见明显反流,肺动脉平均压力与主肺动脉直径(r=0.62, P=0.001)、右肺动脉直径(r=0.63, P=0.01)、射血加速时间(r=-0.55, P=0.005)3个参数有较强相关性.结论 MRI可直接显示肺动脉腔内血栓栓子,诊断急性大面积肺栓塞,并可测量肺动脉血液动力学参数变化,估计肺动脉高压程度,有望成为一种研究肺栓塞的无创性影像方法.     

MRI和心导管检查同步测定肺动脉舒张压的相关性研究

目的　探索MRI无创性测量肺动脉舒张压 (PADP)的新途径。材料与方法　应用MR相位速度图测量 40例具有肺动脉瓣返流 (PR)患者的最大返流速度并计算出舒张末期肺动脉与右心室间的压差 (PVDG) ,同时 ,与右心导管检查结果进行比较 ,通过直线相关与回归分析MRI测量PADP的敏感性和特异性。结果　MRI测定的PADP为 4.82± 1.2 4mmHg(1mmHg =0 .133kPa) ,右心导管的测值为 4.5 2± 2 .0 0mmHg ,二者之间无明显差异 (t=1.45 ,P >0 .0 5 ) ,但具有高度相关性 (r =0 .94,P <0 .0 1)。回归方程y =0 .82x + 4.5 8,其敏感性和特异性高达 90 %。结论　MRI是评价PR患者PADP的较可靠的新技术。     

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。     

磁共振成像对肺动脉栓塞血流动力学的评价

目的:探讨增强磁共振肺灌注成像对肺动脉栓塞血流动力学改变的价值。材料和方法:经放射性核素肺通气-灌注显像和MR肺灌注成像(MRPP)诊断的20例肺动脉栓塞患者和14例健康志愿者,行主肺动脉MR血流编码扫描,通过分析肺实质的信号强度变化率(TROS)、时间-信号曲线、右/左心室内径比及主肺动脉的相关参数(主肺动脉直径、血流峰值、平均流速、单位时间内流量等),比较肺动脉栓塞患者与志愿者间肺动脉血流动力学参数间的差异,评价MR在肺动脉栓塞血流动力学方面的作用。结果:肺栓塞患者组与健康志愿者组肺实质信号强度变化率、峰值时间、主肺动脉直径、右/左心室内径比差异有显著性意义;两组间的主肺动脉峰值流速、平均流速、流量具有统计学差异,肺栓塞患者MR血流编码的肺动脉峰值流速-时间曲线表现为收缩期峰值流时间提前,并可见明显反流。结论:MRI具有诊断肺动脉栓塞的可行性,并可测量肺动脉血流动力学参数变化,粗略估计肺动脉高压程度,有望成为一种研究肺栓塞的无创性影像方法。     

CT肺动脉造影评价慢性血栓栓塞性肺动脉高压的血流动力学

目的 探讨多层螺旋CT肺动脉造影 (CT pulmonary angiography,CTPA)与慢性血栓性肺动脉高压血流动力学关系.方法 回顾性纳入2006-01-2009-10慢性肺栓塞患者55例,评价CT肺动脉栓塞指数(CT pulmonary artery obstruction index, CTPAOI)及CTPA参数.根据CTPA图像采用Qanadli栓塞指数和Mastora栓塞指数计算 CTPAOI.CTPA参数均在轴位图像测量,包括主肺动脉直径、主肺动脉与升主动脉直径比、右室左室直径比等.结果 55例CTEPH患者Qanadli栓塞指数为(37.60±15.22)%,Mastora栓塞指数为(30.02±16.43)%,Qanadli 栓塞指数高于Mastora栓塞指数, Z=-6.296,P=0.000;但二者显著正相关,r =0.875,P=0.000.无论Qanadli栓塞指数还是Mastora栓塞指数与血流动力学参数之间均无显著相关性(P>0.05).CTPA参数与血流动力学参数相关分析显示右室左室直径比与肺动脉收缩压(r=0.240,P=0.021)、肺动脉舒张压(r=0.255,P=0.014)、平均肺动脉压(r=0.217,P=0.037)、肺毛细血管嵌压(r=0.318,P=0.002)、肺血管阻力(r=0.369,P=0.000)呈正相关;右肺动脉干直径、右室与左室比、右室前壁厚度为平均肺动脉压的独立因素.结论 采用Qanadli栓塞指数和Mastora栓塞指数不能反映慢性血栓性肺动脉高压血流动力学变化,但CTPA参数能够从不同方面反映血流动力学状态.     

肺动脉流速的MRI测量与多普勒超声比较研究

目的探讨相位对比法MR I(PC-MR I)测量肺动脉血流的准确性以及临床应用价值。方法①选取正常健康志愿者42例,随机分为2组,采用PC-MR I和多普勒超声测量了主肺动脉的内径、最大流速和平均流速。②采用公式分别计算出主肺动脉1个心动周期的血流量。结果①PC-MR I和多普勒超声测量主肺动脉的内径分别为(24.4±3.41)mm和(21.5±2.55)mm。②PC-MR I测量主肺动脉的最大流速和平均流速分别为(79.9±24.0)cm/s和(50.3±7.71)cm/s。③多普勒超声测量主肺动脉的最大流速和平均流速分别为(88.8±8.33)cm/s和(53.7±5.04)cm/s。④PC-MR I测量主肺动脉的血流量为(73.5±6.60)m l,多普勒超声测量主肺动脉的血流量为(69.0±10.6)m l。应用统计学方法成组样本均数t-检验分析2种测量结果,选择检验水平为α为0.05。结论PC-MR I可以准确测量肺动脉的血流速度和血流量,对评价肺动脉血流动力学的改变具有一定价值。     

基于肺部血流MRI信号在心动周期内变化的灌注成像技术研究

目的探讨血流变化对肺部MRI信号的影响，并研究1种新的MR肺血流灌注成像方法。方法对健康志愿者15例，采用相位对比电影MRI技术测量大肺动脉血流速度和流量在心动周期内的变化；并选用单次激发半傅立叶变换超快速自旋回波序列观察肺实质MR信号的相应改变，评价其相关性；根据不同心动期相肺实质MR信号的差异进行图像减影。结果肺实质．MRI信号表现为心脏收缩期降低，舒张期升高。大肺动脉的瞬时速度、瞬时流量与其呈负相关(r=-0．878、-0．770，P=0，002、0．015)。经肺部MRI信号差异最大的舒张末期和收缩中期的MRI减影可获得肺灌注像。结论肺实质MRI信号的改变与肺血流模式和速度有关。该技术是1种简便易行的非对比剂性的MR肺灌注评价新方法。     

MR相位速度图及多普勒超声对椎动脉血流动力学的对比性研究

目的 评价ＭＲ相位速度图检测椎动脉血流动力学的价值及其诊断椎动脉狭窄的准确性。材料与方法 测量３２列患者的椎动脉直径、流速及最大返流速度并与经颅多普勒超声（ＴＣＤ）进行比较,通过ｔ检验判断椎动脉狭窄患者与对照组之间有无差异以及ｘ＾２检验评判ＭＲ相位速度图测量椎动脉狭窄的准确性和特异性。结果 ＭＲ相位速度图与ＴＣＤＦ的检测结果具有一致性（ｘ＾２＝０．５,Ｐ〉０．０５）;２０例椎动脉狭窄患者的椎动脉流     

MRI测量的目标血管面积与慢性血栓栓塞性肺动脉高压血流动力学参数的相关性研究

目的:探讨MRI测量的肺血管及腔静脉面积与慢性血栓栓塞性肺动脉高压(CTEPH)患者血流动力学参数之间的关系.方法:前瞻性搜集经右心导管检查确诊的慢性血栓栓塞性肺动脉高压患者20例.测量主肺、左右肺动脉、上下腔静脉的平均、最小和最大面积,并与血流动力学参数进行相关性分析.结果:下腔静脉平均、最大面积与肺动脉平均压具有中度相关性(r=0.463、0.447,P=0.040、0.049);下腔静脉平均、最小、最大面积与肺血管阻力指数具有中度相关性(r=0.482、0.444、0.441,P=0.030、0.047、0.049);主肺动脉最小、最大面积(r=0.467、0.468,P=0.044、0.044)及左主肺动脉平均、最小、最大面积(r=0.450、0.468、0.476,P=0.047、0.043、0.039)与右心每博功指数具有中度相关性;左主肺动脉平均、最小、最大面积与右心做功指数具有中度相关性(r=0.473、0.469、0.530,P=0.035、0.043、0.020);上腔静脉平均、最小、最大面积(r=0.516、0.495、0.509,P=0.020、0.031、0.026)及下腔静脉平均、最小、最大面积(r=0.572、0.543、0.445,P=0.008、0.016、0.046)与中心静脉压具有中度相关性.结论:MRI测量的肺动脉及腔静脉面积与CTEPH的血流动力学参数具有中度相关性,而腔静脉面积反映更为全面,对于无创性评估CTEPH患者的病情具有积极意义,并具有潜在的随访应用价值.     

Early onset of retrograde flow in the main pulmonary artery is a characteristic of pulmonary arterial hypertension

Purpose:

To evaluate if early onset of retrograde flow in the main pulmonary artery is a characteristic of pulmonary arterial hypertension (PAH).

Materials and Methods:

Fifty‐five patients with suspected pulmonary hypertension (PH) underwent right‐sided heart catheterization and retrospectively ECG‐gated MR phase‐contrast velocity quantification in the main pulmonary artery. Pulmonary hypertension was defined by a mean pulmonary artery pressure being larger than 25 mmHg. The onset time of the retrograde flow relative to the cardiac cycle duration (Relative Onset Time = ROT) was compared with mean pulmonary artery pressure.

Results:

By the catheterization, 38 patients were identified as having PAH. The ROT for these PAH patients was significantly different from those found in the 17 non‐PH subjects (0.14 ± 0.06 versus 0.37 ± 0.06, P < 0.001). The mean pulmonary artery pressure was related to the ROT (r² = 0.62, P < 0.001) and could be estimated from the ROT with a standard deviation of 11.7 mmHg. With a cutoff value of 0.25, the ROT distinguished PAH patients from non‐PH subjects.

Conclusion:

Early onset of retrograde flow in the main pulmonary artery is a characteristic of pulmonary arterial hypertension and is visible by standard MR phase‐contrast velocity quantification. J. Magn. Reson. Imaging 2011;33:1362–1368. © 2011 Wiley‐Liss, Inc.     

MR相位速度图对椎动脉的血流动力学研究

目的 应用磁共振相位对比法,采用流动分析软件,通过测量椎动脉的流速、流量,评价正常及病理情况下椎动脉血流动力学改变及其意义。方法 测量了８你健康人和１８例椎动脉狭窄时的椎动脉血流变化。采用Ｋ－空间段电影相位速度对比法（Ｓｅｇｍｅｎｔｅｄ Ｋ－ｓｐａｃｅ ｃｉｎｅ ｐｈａｓｅ－ｃｏｎｔｒａｓｔ ＭＲ）测量椎动脉的流量率曲线图,运用统计学分析,比较椎动脉横截面积、流速、流量及其返流量变化情况。结果：Ｍ     

Assessment of coronary flow reserve with fast cine phase contrast magnetic resonance imaging: comparison with measurement by Doppler guide wire.

Fast cine phase contrast magnetic resonance imaging (fast cine phase contrast MRI) can measure phasic coronary flow velocity in humans. The purpose of this study was to compare the coronary flow velocity reserves measured by MR IMAGING with those obtained by Doppler guide wire. Nineteen patients with ischemic or valvular heart disease were studied. Fast cine phase contrast MR images of the left anterior descending (LAD) artery were acquired during breath-hold time in the basal state and after administration of dipyridamole. Flow velocity in the LAD artery was also measured with Doppler guide wire before and after venous injection of dipyridamole in all subjects. Flow velocity in the coronary artery measured with MR IMAGING in the basal state (12.5 +/- 4.9 cm/sec) was significantly lower than that obtained with Doppler guide wire (32.4 +/- 12.1 cm/sec, P < 0.01). However, MR assessments of coronary flow velocity reserve showed a good linear correlation with those measured by Doppler guide wire (r = 0.91). In conclusion, fast cine phase contrast MR imaging is a useful technique, which can provide a noninvasive assessment of flow reserve ratios in patients with coronary artery disease. J. Magn. Reson. Imaging 1999;10:563-568.     

颈动脉狭窄致脑低灌注损伤多模态MRI

目的：探讨颈动脉狭窄程度与颈内动脉血流动力学参数及相关脑区ADC值变化的关系。方法：27例患者经磁共振血管成像（MRA）证实有中度以上颈动脉狭窄。所有患者行颅脑常规 MRI、MRA和DWI检查,并采用血流定量测量（QFlow）和彩色多普勒超声（CDFI）对颈内动脉的血流动力学参数进行分析。对 QFlow技术与CDFI 测量的血流参数（血流量、平均流速、峰值流速及管腔面积）及其与颈动脉狭窄程度及相关脑区的表观扩散系数值（ADC ）之间的相关性行非参数检验。结果：①QFlow技术与CDFI测量的血流量和平均流速呈中度正相关（r＝0．695,P＜0．01;r＝0．795,P＜0．01）,峰值流速和管腔面积呈低度正相关（r＝0．453,P＜0．01;r＝0．573,P＜0．01）。②颈动脉狭窄程度与 QFlow 技术测量的颈内动脉流量呈低度负相关（r＝－0．467,P＜0．01）,与侧脑室旁前部和额叶白质的 ADC 值呈低度正相关（r＝0．373,P＜0．01;r＝0．372,P＜0．01）。③侧脑室旁前部和额叶白质的ADC 值与 QFlow 技术测量的颈内动脉流量分别呈中度和低度负相关（r＝－0．624,P＜0．01;r＝－0．533,P＜0．01）。结论：多模态 MRI能显示颈动脉狭窄所致的颈内动脉血流量减低及供血脑区的低灌注损伤,QFlow技术能较准确评价颈内动脉血流动力学变化。     

Arterial switch procedure for D-transposition of the great arteries: quantitative midterm evaluation of hemodynamic changes with cine MR imaging and phase-shift velocity mapping-initial experience

PURPOSE: To evaluate cine magnetic resonance (MR) imaging and phase-shift velocity mapping for assessment of the hemodynamic relevance of stenotic segments or specific hemodynamic changes in the great vessels after an arterial switch procedure for correction of D-transposition of the great arteries. MATERIALS AND METHODS: Twenty consecutive patients (age range, 2-17 years) with an acoustic window that was insufficient for Doppler transthoracic echocardiography were included in the study. Flow and diameter measurements of the pulmonary arterial trunk and its primary branches were performed with phase-shift velocity mapping and cine MR imaging. RESULTS: There were good correlations between pressure gradients in the pulmonary arteries estimated with MR imaging and those measured with Doppler echocardiography (r = 0.83, n = 15) and cardiac catheterization (r = 0.90, n = 13). Cine MR imaging revealed that the diameters of the right and left pulmonary arteries decreased with the expansion of the aorta during systole, which increased the peak velocity. This temporary stenosis was more severe in the right than in the left pulmonary artery and was accompanied by a significantly (P <.05) lower volume flow in the right artery. CONCLUSION: The anatomic situation after arterial switch repair tended to produce temporary stenoses in the primary pulmonary arterial branches, with significant changes in hemodynamics. These changes may affect the long-term outcome and go undetected with other imaging modalities.     

Pulmonary hypertension: pulmonary flow quantification and flow profile analysis with velocity-encoded cine MR imaging.

Velocity-encoded cine magnetic resonance (MR) imaging provides two-dimensional velocity maps of a cross-sectional area of a vessel. Pulmonary flow and flow patterns in the main pulmonary artery were analyzed with velocity-encoded cine MR imaging and Doppler echocardiography in 10 patients with pulmonary hypertension (PH), one patient with a dilated main pulmonary artery, and 10 healthy subjects, and these findings were compared. Peak systolic velocity measured with velocity-encoded cine MR imaging was similar to that measured with Doppler echocardiography in healthy subjects and in patients with PH. Velocity-encoded cine MR imaging demonstrated substantial differences in velocity across the vascular lumen in PH. The flow pattern in healthy subjects was different than that in patients with PH; the latter had lower peak systolic velocity and greater retrograde flow after middle to late systole. The retrograde flow observed in patients with PH reflected hemodynamic events, since it was inversely proportional to pulmonary flow volume and directly proportional to pulmonary resistance and cross-sectional area of the vessel. Velocity-encoded cine MR imaging demonstrates an inhomogeneous flow profile in PH and may serve as a noninvasive method to estimate pulmonary vascular resistance.     

Flow characteristics of the proximal pulmonary arteries and vena cava in patients with chronic thromboembolic pulmonary hypertension: correlation between 3.0 T phase-contrast MRI and right heart catheterization

PURPOSE

We aimed to determine the correlation between flow characteristics of the proximal pulmonary arteries and vena cava obtained by 3.0 T phase-contrast magnetic resonance imaging (MRI) and hemodynamic characteristics by right heart catheterization in patients with chronic thromboembolic pulmonary hypertension.

MATERIALS AND METHODS

Twenty consecutive patients with chronic thromboembolic pulmonary hypertension and 20 sex- and age-matched healthy volunteers were included prospectively. All patients and controls underwent phase-contrast MRI to determine the flow characteristics including peak velocity, mean velocity, and mean blood flow of the proximal pulmonary artery and vena cava. All patients underwent right heart catheterization to determine the hemodynamics.

RESULTS

Peak velocity and mean velocity of the proximal pulmonary artery were significantly lower in the patient group. In patients, both peak velocity and mean blood flow were sequentially decreased in the main pulmonary artery, left and right pulmonary arteries, and left and right interlobar pulmonary arteries. Inferior vena cava had higher peak velocity, mean velocity, and mean blood flow than superior vena cava. Peak velocity of the main pulmonary artery correlated with mean and diastolic pulmonary artery pressure. Peak velocity of both inferior and superior vena cava strongly correlated with the pulmonary vascular resistance index (PVRI) (r=−0.68, P < 0.001 and r=−0.74, P < 0.001, respectively). Mean velocity of the main pulmonary artery and right pulmonary artery strongly correlated with PVRI and mean pulmonary artery pressure. Mean velocity of the superior vena cava and mean blood flow of the main pulmonary artery strongly correlated with PVRI and right cardiac work index.

CONCLUSION

Blood flow in the proximal pulmonary artery and vena cava evaluated by phase-contrast MRI correlate with hemodynamic parameters of right heart catheterization and can be used to noninvasively evaluate the severity of chronic thromboembolic pulmonary hypertension and, potentially, to follow up the treatment response.Chronic thromboembolic pulmonary hypertension (CTEPH) develops as a result of obstruction of pulmonary arterial vessels by organized thromboembolic material and subsequent vascular remodeling in small unobstructed vessels, and it is associated with significant morbidity and mortality (1). Right heart catheterization remains the reference standard to diagnose CTEPH, assess the hemodynamic disturbance, and follow up the treatment response; but it is invasive, delivers radiation, and is associated with recognized complications (2, 3).Magnetic resonance imaging (MRI) is considered not only as the reference standard for evaluation of ventricular function, but it also provides a reproducible and noninvasive assessment of hemodynamics changes in pulmonary hypertension (4). In a separate validation study, cardiac MRI-derived parameters showed a strong correlation with invasive determinations (5).In a study by Mohiaddin et al. (6), phase-contrast MRI was used to confirm reduced diastolic peak velocity of the inferior vena cava (IVC) in patients with pulmonary hypertension. Only one study reported blood flow conditions in the proximal pulmonary arteries and vena cava in healthy children (7). To our knowledge, no study has assessed proximal pulmonary artery and vena cava flow or evaluated correlation of the flow determined by phase-contrast MRI and hemodynamics by right heart catheterization in CTEPH.We performed a prospective study to observe the flow change in the proximal pulmonary artery, superior vena cava (SVC) and inferior vena cava (IVC) in patients with CTEPH by phase-contrast MRI, and to evaluate the correlation of the proximal pulmonary artery and vena cava flow with hemodynamics derived by right heart catheterization in patients with CTEPH.     

Right and left ventricular stroke volume measurements with velocity-encoded cine MR imaging: in vitro and in vivo validation

The accuracy of measurements of flow velocity determined by using cine MR phase velocity mapping--velocity-encoded cine (VEC) MR--was assessed by comparing VEC MR data with independent measurements in a flow phantom and in human subjects. Constant flow velocities generated in a phantom (range, 20-408 cm/sec) were determined correctly by VEC MR (r = .997, standard error of the estimate [SEE] = 7.9 cm/sec). Peak systolic velocities in the main pulmonary artery determined by VEC MR correlated well with the measurements obtained by using continuous-wave Doppler echocardiography (r = .91). Stroke volumes measured at the aorta by VEC MR and continuous-wave Doppler imaging also correlated well with each other (r = .80). VEC MR measurements of aortic and pulmonary flow provided left and right ventricular stroke volumes that correlated well with left ventricular stroke volumes determined by short-axis cine MR images (r = .98, SEE = 3.7 ml, and r = .95, SEE = 4.8 ml, respectively). Intra- and interobserver variabilities were small for both left and right ventricular stroke volumes as measured with VEC MR. These results indicate that VEC MR accurately and reproducibly measures aortic and pulmonary flow velocities and volumes in the physiologic range of humans, and can be used to measure right and left ventricular stroke volumes under normal flow conditions.