Coronary sinus flow measurement by means of velocity-encoded cine MR imaging: validation by using flow probes in dogs

PURPOSE: To validate coronary sinus flow measurements for quantification of global left ventricular (LV) perfusion by means of velocity-encoded cine (VEC) magnetic resonance (MR) imaging and flow probes. MATERIALS AND METHODS: Measurements of coronary sinus flow were performed in seven dogs by using VEC MR imaging at baseline, single coronary arterial stenosis, dipyridamole stress, and reactive hyperemia. These measurements were compared with flow probe measurements of coronary blood flow (CBF) in the left anterior descending coronary (LAD) and circumflex (CFX) arteries (CBF(LAD+CFX)) and coronary sinus. LV blood perfusion was calculated in milliliters per minute per gram from coronary sinus flow, and LV mass was obtained by using VEC and cine MR imaging. LV mass was validated at autopsy. RESULTS: CBF(LAD+CFX) and coronary sinus flow at VEC MR imaging showed close correlation (r = 0.98, P: <.001). The difference between CBF(LAD+CFX) and MR coronary sinus flow was 3.1 mL/min +/- 8.5 (SD). LV mass at cine MR imaging was not significantly different from that at autopsy (73.2 g +/- 12.8 vs 69. 4 g +/- 12.8). At baseline, myocardial perfusion was 0.40 mL/min/g +/- 0.09 at VEC MR imaging, and CBF(LAD+CFX) was 0.44 mL/min/g +/- 0. 08 (not significant). Reactive hyperemia resulted in 2.7- and 2. 3-fold increases in coronary sinus flow at VEC MR imaging and flow probe CBF(LAD+CFX), respectively. CONCLUSION: VEC MR imaging has the potential to measure coronary sinus flow during different physiologic conditions and can serve as a noninvasive modality to quantify global LV perfusion in patients.     

Velocity and flow quantitation in the superior sagittal sinus with ungated and cine (gated) phase-contrast MR imaging

Normal blood flow and velocity in the superior sagittal sinus were measured in 30 patients. A fast two-dimensional ungated phase-contrast (PC) pulse sequence was compared with a peripherally gated cine PC technique for velocity and flow quantitation. The same imaging parameters were used for both methods. Measured values for mean velocity and flow obtained with the two methods were compared by using regression analysis and t testing. For blood flow, the correlation coefficient was 0.976. For velocity measurements, r was 0.950. Mean flow was 285 mL/min ± 19 with the ungated PC method and 281 mL/min ± 19 with the cine PC method. The mean velocities measured with the two methods were 12.94 cm/sec ± 1.1 and 13.59 cm/sec ± 1.1, respectively. There was no significant difference (paired t test) between the methods for mean flow or velocity data. This was true even though flow in the superior sagittal sinus is moderately pulsatile, as shown with the cine PC technique. The ungated PC method provided these data in 13 seconds versus 3.5 minutes for the cine PC method.     

Hypertrophic cardiomyopathy: MR measurement of coronary blood flow and vasodilator flow reserve in patients and healthy subjects

PURPOSE: To evaluate coronary blood flow per gram of myocardial mass and vasodilator flow reserve in patients with hypertrophic cardiomyopathy (HCM) and in healthy subjects by using breath-hold velocity-encoded cine (VEC) magnetic resonance (MR) imaging. MATERIALS AND METHODS: Twenty-nine patients with HCM and nine healthy volunteers were examined. Fast VEC MR images were obtained in an oblique imaging plane perpendicular to the coronary sinus before and after intravenous injection of dipyridamole (0.56 mg/kg). The products of mean velocity and cross-sectional area of the vessel were integrated to measure blood flow. Breath-hold cine MR images encompassing the entire left ventricle were acquired to quantify the left ventricular mass. RESULTS: In the basal state, the coronary blood flow per gram of myocardial mass was 0.74 mL/min/g +/- 0.23 in healthy subjects and 0.62 mL/min/g +/- 0.27 in patients with HCM. After administration of dipyridamole, coronary blood flow in patients with HCM increased to a level significantly less than that in healthy subjects (1.03 mL/min/g +/- 0.40 vs 2.14 mL/min/g +/- 0.51; P < .01), resulting in a severely depressed flow reserve ratio in patients with HCM compared with that in healthy subjects (1.72 +/- 0.49 vs 3.01 +/- 0.75; P < .01). CONCLUSION: Breath-hold VEC MR imaging is a noninvasive technique for evaluating coronary flow per gram of myocardial mass and coronary flow reserve.     

MR characterization of blood flow in native and grafted internal mammary arteries

In the postoperative patient with anginal symptoms, differentiation between bypass graft compromise and nonischemic causes has until now been accomplished only by means of x-ray angiography. A noninvasive test is clearly desirable. The authors used a cine phase-contrast (PC) magnetic resonance (MR) imaging technique to characterize blood flow in native and grafted internal mammary arteries (IMAs). Ten volunteers and 15 patients who had recently undergone IMA coronary artery bypass grafting were imaged. Cine PC MR imaging was performed in the transaxial plane at the level of the pulmonary artery bifurcation. Flow in both IMAs was quantified and expressed as a percentage of cardiac output measured in the ascending aorta. In the 15 patients, flow analysis was performed in both the native and grafted IMAs. In the volunteers, IMA blood flow ranged from 2.1% to 4.3% of cardiac output on the left (mean, 3.5%) and 2.1% to 5.1% (mean, 3.5%) on the right. There was considerable intersubject variability, with coefficients of variation of 10.7% for the left and 12.3% for the right IMA. Intrasubject variability was limited, with estimated common standard deviations of 0.45% of cardiac output (range, 0.2%–1.1%) for the left and 0.39% (range, 0.1%–0.6%) for the right IMA. Flow in grafted IMAs was identified in 13 of 15 patients. In one of two patients without demonstrable IMA graft flow, cardiac catheterization confirmed lack of flow. IMA graft flow varied from 28 to 164 mL/min (mean, 80.3 mL/min). This study shows the feasibility of using cine PC MR imaging as a quantitative method of evaluating blood flow in IMA coronary artery bypass grafts.     

Chronic heart failure: global left ventricular perfusion and coronary flow reserve with velocity-encoded cine MR imaging: initial results

PURPOSE: To quantify and compare global left ventricular (LV) perfusion and coronary flow reserve (CFR) in patients with chronic heart failure and in healthy volunteers by measuring coronary sinus flow with velocity-encoded cine (VEC) magnetic resonance (MR) imaging. MATERIALS AND METHODS: MR measurements were performed in 10 consecutive patients with chronic heart failure due to coronary artery disease and in 10 volunteers. Global LV perfusion was quantified by measuring coronary sinus flow in an oblique imaging plane perpendicular to the coronary sinus with non-breath-hold VEC MR imaging. LV mass was measured by means of cine imaging that encompassed the heart. LV perfusion was calculated from coronary sinus flow and mass. CFR was measured from LV perfusion at rest and that after infusion of dipyridamole. Analysis of covariance was used to determine differences between groups. Differences within groups were analyzed by means of the Student t test for paired data. Regression analysis was used to determine correlation between CFR and LV ejection fraction. RESULTS: At rest, LV perfusion was not significantly different in patients with chronic heart failure (0.46 mL/min/g +/- 0.19) and volunteers (0.52 mL/min/g +/- 0.21, P =.54). After administration of dipyridamole, LV perfusion was less than half in patients with chronic heart failure compared with that in volunteers (1.07 mL/min/g +/- 0.64 vs 2.19 mL/min/g +/- 0.98) (P =.03). CFR was severely reduced in patients with chronic heart failure compared with that in volunteers (2.3 +/- 0.9 vs 4.2 +/- 1.5, P =.01). A moderate but significant correlation was found between CFR and LV ejection fraction (r = 0.54, P =.02) CONCLUSION: Combined cine and VEC MR imaging revealed that patients with chronic heart failure have normal LV perfusion at rest but severely depressed LV perfusion after vasodilation. Impaired CFR may contribute to progressive decline in LV function in patients with chronic heart failure.     

evaluation of communication between intracranial arachnoid cysts and cisterns with phase-contrast cine MR imaging

BACKGROUND AND PURPOSE: The demonstration of communication between arachnoid cysts (ACs) and the adjacent subarachnoid space is a prerequisite for their proper management. CT cisternography (CTC) is the conventional method for functional evaluation of ACs. The sensitivity of MR imaging to CSF flow has been demonstrated, but reports of the clinical usefulness of MR CSF flow techniques in this application are limited. The purpose of our study was to prospectively evaluate the accuracy of MR CSF flow study as an alternative to CTC in this setting. METHODS: MR CSF flow study with retrospective ECG-gated 2D, fast low-angle shot, phase-contrast (PC), cine gradient-echo sequence was performed in 39 patients with an intracranial AC. Results were compared with intraoperative and CTC findings. RESULTS: PC cine MR imaging results were compatible with operative or CTC findings in 36 (92.3%) of 39 patients. Twenty-four cysts were noncommunicating, and 15 were communicating. Three cysts were evaluated as being noncommunicating on PC cine MR imaging (false-negative) but demonstrated contrast enhancement on CTC. No false-positive diagnoses occurred. All cysts regarded as being communicating on PC cine MR imaging were also found to be communicating on both confirmation methods. CONCLUSION: MR CSF flow imaging with a PC cine sequence can be incorporated in the imaging work-up of ACs. This is a reliable alternative to invasive CTC for the functional evaluation of ACs.     

Comparison of cerebral artery blood flow measurements with gated cine and ungated phase-contrast techniques

Cine phase-contrast (PC) magnetic resonance (MR) pulse sequences have been used to measure blood flow in a variety of vessels. Because the cine PC sequence is time-consuming, this prospective study was undertaken to compare it with an ungated PC technique for measuring average blood flow in individual cerebral arteries to potentially achieve substantial time savings. The following cerebral arteries were studied in 10 healthy volunteers: carotid, basilar, middle cerebral, anterior cerebral, and posterior cerebral. Imaging planes were placed perpendicular to the vessel of interest, and velocity encoding, ranging from 40 to 250 cm/sec, was matched to individual arteries. Good correlation between cine and ungated PC blood flow measurements was obtained for both high- and low-flow vessels, with an overall correlation coefficient of 978. The ungated PC sequence, because of its short imaging time, allows measurement of the blood volume flow rate in the circle of Willis in approximately 20 minutes, a clinically acceptable time.     

MR measurement of coronary blood flow.

The functional significance of coronary arterial stenosis can be evaluated by measuring the pharmacological flow reserve. Magnetic resonance (MR) imaging has a unique potential for noninvasive measurement of coronary blood flow and flow reserve in the native coronary artery and bypass graft. Restenosis after coronary balloon angioplasty and stenting in the left anterior descending artery can be detected noninvasively with serial MR measurements of the coronary flow reserve. Further refinement of the MR pulse sequences to improve spatial and temporal resolutions may permit accurate quantification of blood flow volume and flow reserve in all major coronary arterial branches. MR assessments of blood flow volume and flow pattern allow noninvasive detection of significant stenosis in the coronary artery bypass graft as well. By integrating MR blood flow measurement in the coronary sinus and cine MR assessment of left ventricular myocardial mass, altered myocardial micro-circulation in patients with diffuse myocardial diseases, such as hypertrophic cardiomyopathy and cardiac transplant, has been documented. J. Magn. Reson. Imaging 1999;10:728-733.     

Quantitative analysis of first‐pass contrast‐enhanced myocardial perfusion MRI using a patlak plot method and blood saturation correction

The objectives of this study were to develop a method for quantifying myocardial K₁ and blood flow (MBF) with minimal operator interaction by using a Patlak plot method and to compare the MBF obtained by perfusion MRI with that from coronary sinus blood flow in the resting state. A method that can correct for the nonlinearity of the blood time–signal intensity curve on perfusion MR images was developed. Myocardial perfusion MR images were acquired with a saturation‐recovery balanced turbo field‐echo sequence in 10 patients. Coronary sinus blood flow was determined by phase‐contrast cine MRI, and the average MBF was calculated as coronary sinus blood flow divided by left ventricular (LV) mass obtained by cine MRI. Patlak plot analysis was performed using the saturation‐corrected blood time–signal intensity curve as an input function and the regional myocardial time–signal intensity curve as an output function. The mean MBF obtained by perfusion MRI was 86 ± 25 ml/min/100 g, showing good agreement with MBF calculated from coronary sinus blood flow (89 ± 30 ml/min/100 g, r = 0.74). The mean coefficient of variation for measuring regional MBF in 16 LV myocardial segments was 0.11. The current method using Patlak plot permits quantification of MBF with operator interaction limited to tracing the LV wall contours, registration, and time delays. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.     

Accelerated phase-contrast cine MRI using k-t SPARSE-SENSE

Phase-contrast (PC) cine MRI is a promising method for assessment of pathologic hemodynamics, including cardiovascular and hepatoportal vascular dynamics, but its low data acquisition efficiency limits the achievable spatial and temporal resolutions within clinically acceptable breath-hold durations. We propose to accelerate PC cine MRI using an approach which combines compressed sensing and parallel imaging (k-t SPARSE-SENSE). We validated the proposed 6-fold accelerated PC cine MRI against 3-fold accelerated PC cine MRI with parallel imaging (generalized autocalibrating partially parallel acquisitions). With the programmable flow pump, we simulated a time varying waveform emulating hepatic blood flow. Normalized root mean square error between two sets of velocity measurements was 2.59%. In multiple blood vessels of 12 control subjects, two sets of mean velocity measurements were in good agreement (mean difference = -0.29 cm/s; lower and upper 95% limits of agreement = -5.26 and 4.67 cm/s, respectively). The mean phase noise, defined as the standard deviation of the phase in a homogeneous stationary region, was significantly lower for k-t SPARSE-SENSE than for generalized autocalibrating partially parallel acquisitions (0.05 ± 0.01 vs. 0.19 ± 0.06 radians, respectively; P < 0.01). The proposed 6-fold accelerated PC cine MRI pulse sequence with k-t SPARSE-SENSE is a promising investigational method for rapid velocity measurement with relatively high spatial (1.7 mm × 1.7 mm) and temporal (～35 ms) resolutions.     

Myocardial blood flow in patients with dilated cardiomyopathy: quantitative assessment with velocity-encoded cine magnetic resonance imaging of the coronary sinus

PURPOSE: To quantify global myocardial perfusion using magnetic resonance imaging (MRI) in patients with heart failure due to idiopathic dilated cardiomyopathy (IDC) and to compare myocardial perfusion and microvascular reactivity with healthy subjects. MATERIALS AND METHODS: A total of 19 subjects (healthy volunteers (N = 12) and IDC patients (N = 7)) were studied using cine MRI to measure left ventricular (LV) mass and a velocity-encoded cine MRI technique to measure coronary sinus flow at rest and after dipyridamole-induced hyperemia. Absolute values of total myocardial blood flow (MBF) were calculated from coronary sinus flow and LV mass. RESULTS: At baseline, MBF was not significantly different in patients with IDC (0.48 +/- 0.07 mL/minute/g) and healthy subjects (0.55 +/- 0.19 mL/minute/g, P= 0.41). After dipyridamole administration, MBF in IDC patients increased to a level significantly less than that in normal volunteers (1.05 +/- 0.35 mL/minute/g vs. 1.99 +/- 1.05 mL/minute/g, P < 0.05). Consequently, MBF reserve was impaired in patients with IDC (2.19 +/- 0.77) compared to that in healthy subjects (3.51 +/- 1.29, P < 0.05). A moderate correlation was found between MBF reserve and LV ejection fraction (r = 0.48, P < 0.05). CONCLUSION: MBF reserve is reduced in patients with IDC, indicating that coronary microcirculatory flow is impaired. This integrated MRI approach allows quantitative measurement of global MBF in humans and may have the potential to study the effects of pharmacological interventions on myocardial perfusion.     

横窦血液流量MR测量方法的比较研究

目的 通过与电影相位对比（PC）法和超声的比较，评价二维（2D）PC法测量横窦血液流速和流量的准确性。方法 （1）志愿者8例，共计测量12个横窦，在每个横窦相同层面上分别采用2DPC法和电影PC法进行血流信号面积，血液流速和流量测量，测量结果用配对t检验进行统计分析。（2）需要开颅手术患者5例。共计6个横窦，术前采用2DPC方法对横窦血液流速进行测量，术中暴露横窦以后，用TCD探测血液流速，测量结果采用相关回归分析。结果 统计结果表明：2DPC法和电影PC法测得的横窦血流信号面积（t=-1.106,P=0.293)。流速（t=0.262,P=0.798)和流量（t=0.439,P=0.669)均无显著性差异，2DPC测得的流速与TCD测得的流速相关性良好（y^=1.303x 0.62,r^2=0.88)。结论 2DPC法是测量横窦血液流量简便实用的方法。     

颅内疾病对导水管脑脊液流量的影响

目的：探讨用磁共振相位对比电影(PC cine)对导水管脑脊液定量测量的临床应用价值。方法：将35例中枢神经系统不同疾病分三组，用PC cine方法进行导水管脑脊液流量测量。结果：在脑血管病组伴白质改变时导水管流量增加；梗阻性脑积水导水管流量减少，流动波形异常；交通性脑积水导水管流量增加，波形圆钝。结论：磁共振PC cine方法测量导水管脑脊液流量简单易行，可为临床提供更多的影像信息。     

Popliteal and tibioperoneal arteries: feasibility of two-dimensional time-of-flight MR angiography and phase velocity mapping.

To assess the feasibility of using magnetic resonance (MR) angiography and velocity-encoded cine MR imaging to evaluate morphology and function in the popliteal and tibioperoneal arteries, the profiles of blood flow velocity measured with velocity-encoded cine MR were compared with those measured with color-coded sonography. Two-dimensional time-of-flight MR angiography was performed in the popliteal and tibioperoneal arteries of 10 healthy subjects; velocity-encoded cine MR and color-coded sonography were performed above and below the trifurcation. The velocity waveforms acquired with velocity-encoded cine MR and color-coded sonography correlated well and showed a typical triphasic pattern. At peak systole in the popliteal artery, spatial maximum and spatial mean velocities measured with velocity-encoded cine MR were 42.29 cm/sec +/- 9.55 (standard deviation) and 27.7 cm/sec +/- 5.8, respectively; the peak velocity measured with color-coded sonography was 44.2 cm/sec +/- 12.3. It is concluded that use of both MR angiography and velocity-encoded cine MR should be considered for identification of arterial stenoses and assessment of the hemodynamic importance of peripheral vascular stenoses.     

SPAMM, cine phase contrast imaging and fast spin-echo T2-weighted imaging in the study of intracranial cerebrospinal fluid (CSF) flow

AIM: To compare the qualitative assessment of cerebrospinal fluid (CSF) flow using a SPAMM (spatial modulation of magnetization) technique with cine phase contrast images (cine PC) and fast spin echo (FSE) T2-weighted images. MATERIALS AND METHODS: SPAMM, PC and T2-weighted sequences were performed on 22 occasions in 19 patients. Eleven of the studies were performed following a neuroendoscopic third ventriculostomy (NTV), and in these cases, the success of the NTV was determined by clinical follow-up. Two observers used consensus to grade the presence of CSF flow at nine different sites for each study. RESULTS: At 14 of the 178 matched sites, which could be assessed by both SPAMM and cine PC, SPAMM CSF flow grade was higher than that of cine PC. At a further 14/178 matched sites, the cine PC grade was higher than that of SPAMM. There was definite CSF flow at 113/182 (62%) of all the cine PC sites assessed, and 110/181 (61%) of all SPAMM sites assessed whilst 108/198 (54%) of FSE T2-weighted image sites demonstrated flow voids. Cine PC grades were higher than SPAMM at the cerebral aqueduct (P < 0.05, Wilcoxon sign rank test). Definite CSF flow within the anterior third ventricle was present in 4/5 (SPAMM) and 3/5 (cine PC) successful NTVs, 0/2 (SPAMM and cine PC) unsuccessful NTVs and 1/10 (SPAMM and cine PC) patients without NTV. CONCLUSION: SPAMM provides a comparable assessment of intracranial CSF flow to that of cine phase contrast imaging at all CSF sites except the cerebral aqueduct.     

电影相位对比与屏气二维相位对比MRI对肝硬化门静脉血流的对照研究

目的探讨MRI电影法相位对比（Cine PC）与屏气二维相位对比（2D PC）在肝硬化患者和正常志愿者门静脉血流测量中的诊断价值。资料与方法对照组为82名志愿者,男45名,女37名,平均年龄26.65岁;肝硬化组24例,男14例,女10例,平均年龄42.00岁。空腹状态下采用CinePC技术对门静脉血流定量测量,同期采用2DPC技术3种不同屏气状态（正常吸气屏气,呼气屏气,平静呼吸屏气）与其进行比较。结果肝硬化患者门静脉血流速度较对照组略减低,除2D PC平静呼吸法,余方法两组差异均无统计学意义,肝硬化组门静脉血流量与对照组比较明显增大（P〈0.01）,但2DPC吸气屏气技术两者差异无统计学意义。采用相关性分析对屏气2DPC（不同呼吸状态）与Cine PC MRI方法定量门静脉血流速度、血流量,显示两种技术相关性很好（r〉0.8;P〈0.01）,但在对照组行相关性分析,仅呼气后屏气2D PC与Cine PC显示中度相关（r〉0.5;P〈0.01）,吸气后屏气与CinePC相关性较差（r〈0.4）。结论MRI Cine PC在正常呼吸情况下对门静脉血流行定量测量,接近人体生理状态,适合门静脉血流测量;正常呼吸状态屏气对肝硬化患者门静脉血流影响较正常人小,在肝硬化血流测量中,MRI Cine PC与屏气2DPCMRI法显示很好相关性。屏气2DPCMRI技术提供了一种简便、实用、相对准确的肝硬化门静脉血流测量方法。     

Quantitation of flow in the superior sagittal sinus performed with cine phase-contrast MR imaging of healthy and achondroplastic children

BACKGROUND AND PURPOSE: Cine phase-contrast (PC) MR imaging is a convenient and effective method for measuring volumetric flow rates in vivo. We attempted to evaluate changes in blood flow in the superior sagittal sinus (SSS) in children and to assess the hypothesis that restricted venous outflow attributable to stenosis of the jugular vein causes hydrocephalus in achondroplasia. METHODS: Blood flow in the SSS was measured by using cine PC MR imaging with a 1.5-T scanner. After validation, 35 neurologically healthy children as well as eight children with achondroplasia (five with hydrocephalus) and two children with obstructive hydrocephalus were studied. Average flow velocity over the cardiac cycle and volumetric flow rate in the SSS were obtained. The data for healthy children were plotted as a function of age, and reference values were defined by using a five-point smoothing. RESULTS: In healthy children, flow velocity ranged from 92 to 196 mm/s (mean, 136), and flow rate from 189 to 688 mL/min (mean, 484). The flow rate showed changes statistically related to age. It rapidly increased during the first 2 years and reached a peak by 6 to 8 years of age. The flow velocity showed a similar pattern, but not with significant correlation. In all cases of achondroplasia with hydrocephalus, both flow values were reduced below the reference values minus one standard deviation. In cases of achondroplasia without hydrocephalus, and in obstructive hydrocephalus, the values were not reduced. CONCLUSION: Blood flow in the SSS reflects brain maturation. Hydrocephalus associated with achondroplasia was found to be closely related to reduced flow in the SSS, which supports the hypothesis that restricted venous outflow causes hydrocephalus in cases of achondroplasia.     

Hemodynamic assessment in a child with renovascular hypertension using time‐resolved three‐dimensional cine phase‐contrast MRI

Renovascular hypertension (RVH) is an important cause of hypertension in children. It is essential to assess the hemodynamics of RVH lesions in detail. We herein report the case of a 9‐year‐old female with RVH caused by left renal artery stenosis in which the hemodynamics of the lesions were assessed with time‐resolved three‐dimensional cine phase‐contrast MRI (3D cine PC MRI) with a vastly undersampled 3D radial projection imaging trajectory before and after percutaneous transluminal renal angioplasty (PTRA). The utility of 3D cine PC MRA for diagnosing RVH and evaluating the renal blood flow pre‐ and post‐PTRA is presented. J. Magn. Reson. Imaging 2015;41:165–168. © 2014 Wiley Periodicals, Inc .     

Velocity-encoded,phase-difference cine MRI measurements of coronary artery flow: Dependence of flow accuracy on the number of cine frames

Phase-contrast magnetic resonance imaging (PC-MRI) can be used to produce multiframe cine flow images of the coronary arteries. Accurate coronary flow measurement requires the elimination of respiratory motion artifacts using k-space segmentation to acquire the data in a single breath-hold. However, the duration of the breath-hold is proportional to the number of cine frames. In the present study, the number of cine frames was varied and the accuracies of the coronary flow measurements were assessed using perivascular US. For the range of flows studied (2 ml/min to 147 ml/min), the correlation coefficients for PC-MRI and US increased (.70–.98) and the limits of agreement improved (±45 ml · min^?1 to ± 10 ml · min^?1) as the number of cine frames increased from one to six. The results suggest that the accuracy of breath-hold cine PC-MRI measurements of coronary artery flow improves as the number of cine frames increases.