MR phase-shift velocity mapping of mitral and pulmonary venous flow

Mitral and pulmonary venous flows are important indexes in the evaluation of left ventricular diastolic function and in the assessment of mitral valve disease. We used MR phase-shift velocity mapping to measure mitral and pulmonary venous flow velocity in 10 healthy volunteers and mitral flow velocity in 5 patients with mitral valve stenosis. Normal mitral flow shows two positive peaks: one during early ventricular diastole and the other during atrial contraction. Peak mitral flow velocity (mean +/- SD) in early diastole was 68 +/- 12 cm/s and during atrial contraction 39 +/- 10 cm/s. The ratio of peak mitral flow velocity in early diastole to that during atrial contraction was 1.9 +/- 0.6. In patients with mitral valve stenosis, the initial high flow velocity persisted through diastole. Peak mitral flow velocity of patients with mitral valve stenosis correlated well with values obtained from Doppler echocardiography. Pulmonary venous flow showed two positive peaks: one during ventricular systole and the other in ventricular diastole. A small backflow during atrial contraction was noticed. Peak systolic velocity in the right lower pulmonary vein was 47 +/- 11 cm/s, peak diastolic velocity was 40 +/- 9 cm/s, and peak backflow velocity was 14 +/- 3 cm/s. Magnetic resonance velocity mapping is a noninvasive technique for the evaluation of time-related flow velocity patterns and for quantitative measurement of mitral and pulmonary venous blood flow velocity.     

Flow profiles in the left anterior descending and the right coronary artery assessed by MR velocity quantification: effects of through-plane and in-plane motion of the heart.

PURPOSE: The purpose of this work was to compare the temporal profiles of volume flow in the left anterior descending artery (LAD) and the right coronary artery (RCA) and to assess the effect of through-plane and in-plane myocardial motion. METHOD: In eight healthy volunteers, MR phase-difference velocity quantification was applied with prospective ECG triggering, pixel size of 1.16 x 0.98 mm2 (LAD) or 1.25 x 0.98 mm2 (RCA), velocity sensitivity of 40 cm/s, and data acquisition time window of 64 ms for LAD (3 ky lines per heartbeat) and 24 ms for RCA. In-plane motion was measured from the magnitude images. RESULTS: In the LAD, systolic peak and mean flow values were 0.94+/-0.28 and 0.30 +/-0.22 ml/s, respectively. Diastolic peak and mean flows were 2.42+/-0.56 and 1.38+/-0.43 ml/s. The systolic to diastolic ratio was 0.37+/-0.12 for peak flow and 0.22+/-0.15 for mean flow. Mean flow through the cardiac cycle was 59.1+/-15.0 ml/min. In the RCA, systolic peak and mean flow values were 1.96+/-0.69 and 0.74+/-0.31 ml/s, respectively. Diastolic peak and mean flows were 1.80+/-0.53 and 0.83+/-0.20 ml/s. The systolic to diastolic ratio was 0.97+/-0.58 for peak flow and 0.85+/-0.39 for mean flow. Mean flow through the cardiac cycle was 38.4+/-10.8 ml/min. The in-plane velocity of the coronary artery cross-section was 6.4+/-1.8 cm/s for the LAD and 14.9 +/-4.0 cm/s for the RCA (given by peak values in diastole). CONCLUSION: It is confirmed noninvasively with MR that the LAD shows a predominantly diastolic flow, whereas the RCA shows about equal flow values in systole and diastole. Through-plane motion correction is required for assessing the true flow patterns. The in-plane velocities of the coronary artery cross-sections imply a maximum data acquisition time window, estimated at 58 ms for the LAD and at 23 ms for the RCA.     

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.     

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.     

Assessing coronary sinus blood flow in patients with coronary artery disease: a comparison of phase-contrast MR imaging with positron emission tomography

OBJECTIVE: This study was performed to determine whether MR imaging can be used to reliably measure global myocardial blood flow and coronary flow reserve in patients with coronary artery disease as compared with such measurements obtained by positron emission tomography (PET). SUBJECTS AND METHODS: We measured myocardial blood flow first at baseline and then after dipyridamole-induced hyperemia in 20 patients with coronary artery disease. Myocardial blood flow as revealed by MR imaging was calculated by dividing coronary sinus flow by the left ventricular mass. Coronary flow reserve was calculated by dividing the rate of hyperemic flow by the rate of baseline flow. RESULTS: Using MR imaging, myocardial blood flow at baseline was 0.73 +/- 0.23 mL x min(-1) x g(-1), and at hyperemia the blood flow was 1.43 +/- 0.37 mL x min(-1) x g(-1), yielding an average coronary flow reserve of 1.99 +/- 0.47. Using PET, myocardial blood flow was 0.89 +/- 0.21 mL x min(-1) x g(-1) at baseline and 1.56 +/- 0.42 mL x min(-1) x g(-1) at hyperemia, yielding an average coronary flow reserve of 1.77 +/- 0.36. The correlation of myocardial blood flow and coronary flow reserve measurements for these two methods was an r of 0.80 (p < 0.01) and an r of 0.50 (p < 0.05), respectively. CONCLUSION: This study shows that myocardial blood flow measurements obtained using MR imaging have a good correlation with corresponding PET measurements. Coronary flow reserve measurements obtained using MR imaging had only moderate correlation with PET-obtained measurements. Our results suggest that MR imaging flow quantification could potentially be used for measuring global myocardial blood flow in patients in whom interventional treatment for coronary artery disease is being evaluated.     

Simultaneous measurement of blood and myocardial velocity in the rat heart by phase contrast MRI using sparse q-space sampling

PURPOSE: To measure cardiac blood flow patterns and ventricular wall velocities through the cardiac cycle in anesthetized Wistar Kyoto (WKY) rats. MATERIALS AND METHODS: A gradient-echo cine pulse sequence incorporating pulsed field gradients (PFGs) provided phase contrast (PC) motion encoding. We achieved a range of velocity sensitivity that was sufficient to measure simultaneously the large flow velocities within the cardiac chambers and aortic outflow tract (up to 70 cm s(-1) during systole), and the comparatively small velocities of the cardiac wall (0-3 cm s(-1)). A scheme of sparsely sampling q-space combined with a probability-based method of velocity calculation permitted such measurements along three orthogonal axes, and yielded velocity vector maps in all four chambers of the heart and the aorta, in both longitudinal and transverse sections, for up to 12 time-points in the cardiac cycle. RESULTS: Left ventricular systole was associated with a symmetrical laminar flow pattern along the cardiac axis, with no appearance of turbulence. In contrast, blood showed a swirling motion within the right ventricle (RV) in the region of the pulmonary outflow tract. During left ventricular diastole a plume of blood entered the left ventricle (LV) from the left atrium. The ventricular flow patterns could also be correlated with measurements of left ventricular wall motion. The greatest velocities of the ventricular walls occurred in the transverse cardiac plane and were maximal during diastolic refilling. The cardiac wall motion in the longitudinal axis demonstrated a caudal-apical movement that may also contribute to diastolic refilling. CONCLUSION: The successful measurements of blood and myocardial velocity during normal myocardial function may be extended to quantify pathological cardiac changes in animal models of human cardiac disease.     

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.     

Left-to-right cardiac shunts: comparison of measurements obtained with MR velocity mapping and with radionuclide angiography

PURPOSE: To investigate the agreement between two noninvasive methods, magnetic resonance (MR) velocity mapping and first-pass radionuclide angiography, to quantify the pulmonary-to-systemic blood flow ratio (QP/QS) in adults, adolescents, and children with left-to-right cardiac shunts. MATERIALS AND METHODS: The accuracy and precision of MR velocity mapping were studied in 12 control subjects (six men, six women) and in a phantom. MR velocity mapping and radionuclide angiography were performed on the same day in 24 patients (16 adults, two adolescents, six children; five male patients, 19 female patients). RESULTS: The mean error in QP/QS at MR velocity mapping in phantom experiments was -1% +/- 1 (mean +/- SD). In control subjects, QP/QS at MR velocity mapping was 1.03 +/- 0.03, and the cardiac index was 3.1 L/min/m2 +/- 0.2 and 3.2 L/min/m2 +/- 0.3 for women and men, respectively. In patients, QP/QS at radionuclide angiography was 14% +/- 13, higher than at MR velocity mapping. Interobserver variability was four times higher for radionuclide angiography compared with MR velocity mapping, 0% + 16 versus 0% +/- 4 (n = 12). The difference between repeated MR flow measurements in the same vessel was -1% +/- 5 (n = 36). CONCLUSION: The data suggest that MR velocity mapping is accurate and precise for measurements of shunt size over the whole range of possible QP/QS values.     

Arterial and venous blood flow: noninvasive quantitation with MR imaging.

Quantitative measurements of arterial and venous blood flow were obtained with phase-contrast cine magnetic resonance (MR) imaging and compared with such measurements obtained by means of implanted ultrasound (US) blood flow probes in anesthetized dogs. The US flowmeter was enabled during a portion of each MR imaging sequence to allow virtually simultaneous data acquisition with the two techniques. MR imaging data were gated by means of electrocardiography and divided into 16 phases per cardiac cycle. The rates of portal venous blood flow measured with MR imaging and averaged across the cardiac cycle (710 mL/min +/- 230 [standard deviation]) correlated well with those measured with the flowmeter and averaged in like fashion (751 mL/min +/- 238) (r = .995, slope = 1.053). The correspondence in arterial blood flow was almost as good. No statistically significant difference existed between the paired measurements of blood flow obtained with MR imaging and the implanted probe. It is concluded that, as a noninvasive means of accurate quantification of blood flow, phase-contrast MR imaging may be especially useful in deep blood vessels in humans.     

Echocardiographic evaluation of left ventricular diastolic function in patients with aortic valve stenosis

Impairment of left ventricular diastolic function in aortic valve stenosis occurs very early and precedes the impairment of systolic function. Aim was to examine left ventricular diastolic function and its association with severity of myocardial hypertrophy and clinical picture. The paper comprised 78 patients with isolated aortic valve stenosis in whom were performed ultrasonography and catheterization. No significant differences in parameters of diastolic filling were observed in patients with mild hypertrophy and preserved systolic function compared to healthy subjects. In patients with moderate myocardial hypertrophy, left ventricular filling was decreased in an early diastole (Emax 51 +/- 5 cm/s, Evti 6.4 +/- 1.1 cm) and increased in late diastole (Amax 88 +/- 11 cm/s, Avti 11.4 +/- 1.8 cm), while deceleration time was prolonged (DT 171 +/- 32 ms). Pulmonary vein flow was decreased during diastole (Dmax 33 +/- 5 cm/s, Dvti 7.6 +/- 2 cm). Pseudonormalization of flow through mitral valve was observed in patients with pronounced hypertrophy of left ventricular wall (mass > 180 g/m2): increase of the velocity during the phase of fast left ventricular filling (Emax 72 +/- 13 cm/s, Evti 9.8 +/- 2.1 cm), decrease during atrial contraction (Amax 31 +/- 6 cm/s, Avti 3.7 +/- 0.4 cm), reduction in deceleration time (DT 116 +/- 11 ms), while pulmonary vein flow velocity was increased during the early diastole (Dmax 64 +/- 17 cm/s, Dvti 10.7 +/- 2.2 cm). Likewise, significant correlation between clinical picture and type of blood flow through mitral valve was observed.     

In-plane coronary arterial motion velocity: measurement with electron-beam CT

PURPOSE: To determine the speed of and changes in the speed of coronary arterial movement during the cardiac cycle with electron-beam computed tomography (CT). MATERIALS AND METHODS: With electron-beam CT, 20 consecutive cross-sectional images were acquired at the mid right coronary artery (with 50-msec acquisition time, 8-msec intersection delay, 7-mm section thickness, and intravenous administration of 40 mL of contrast agent) in 25 patients. On the basis of the displacement of the left anterior descending, left circumflex, and right coronary arterial cross sections from image to image, movement velocity in the transverse imaging plane was calculated and was correlated with the simultaneously recorded electrocardiogram. RESULTS: The velocity of in-plane coronary arterial motion varied considerably during the cardiac cycle. Peaks were caused by ventricular systole and diastole and by atrial contraction. The mean velocity was 46.6 mm/sec +/- 12. 5 (SD). The mean velocity of right coronary arterial movement (69.5 mm/sec +/- 22.5) was significantly faster than that of the left anterior descending (22.4 mm/sec +/- 4.1) or the left circumflex coronary artery (48.4 mm/sec +/- 15.0). The lowest mean velocity (27. 9 mm/sec) was at 48% of the cardiac cycle. CONCLUSION: The lowest velocity of coronary arterial movement, which displays considerable temporal variation, was at 48% of the cardiac cycle.     

基于超声多普勒组织成像的人工起搏状态下心肌运动速度特征研究

目的定量分析希氏束 (His)人工起搏状态下的心肌运动速度特征 ,探索心肌运动模式。方法采用二维彩色超声组织多普勒速度成像模式 ,观察、记录 5条犬在His以 1 2 0次心率人工起搏状态下的His周和室间隔 (interventricularseptum ,IVS)心肌运动 ,对保存的图像序列进行后处理以得到心肌速度值序列 ,然后对此序列值进行分析。结果得到心肌连续时间—速度曲线 ,根据曲线得到 :His周心肌收缩舒张时间 ( 2 0 9.75± 1 9.41 )ms和 ( 2 94.5 0± 1 7.87)ms、收缩速度 (S) ( 5 .43± 1 .5 3)cm/s、舒张早期速度 (E)( 3.95± 1 .1 8)cm/s、舒张末期速度 (A) ( 1 .72± 0 .77)cm/s、E/A为 2 .0 6± 0 .95 ;IVS心肌收缩舒张时间( 1 91 .33± 1 7.2 3)ms和 ( 2 94.70± 1 7.91 )ms、S为 ( 3.1 7± 1 .34)cm/s、E为 ( 2 .1 7± 0 .64)cm/s、A为 ( 1 .48± 0 .5 2 )cm/s、E/A为 1 .30 5± 0 .2 87。结论在His人工起搏状态下 ,心肌运动的初步特征为 :1 )His周比IVS心肌运动速度大。 2 )E/A大于 1。     

High-resolution blood flow velocity measurements in the human finger.

MR phase contrast blood flow velocity measurements in the human index finger were performed with triggered, nontriggered, and cine acquisition schemes. A strong (G(max) = 200 mT/m), small bore (inner diameter 12 cm) gradient system inserted in a whole body 3 Tesla MR scanner allowed high-resolution imaging at short echo times, which decreases partial volume effects and flow artifacts. Arterial blood flow velocities ranging from 4.9-19 cm/sec were measured, while venous blood flow was significantly slower at 1.5-7.1 cm/sec. Taking into account the corresponding vessel diameters ranging from 800 microm to 1.8 mm, blood flow rates of 3.0-26 ml/min in arteries and 1.2-4.8 ml/min in veins are obtained. The results were compared to ultrasound measurements, resulting in comparable blood flow velocities in the same subjects. Magn Reson Med 45:716-719, 2001.     

Theory of high-speed MR imaging of the human heart with the selective line acquisition mode

PURPOSE: To validate a recently developed fast high-temporal-resolution magnetic resonance (MR) flow sequence and use it to assess coronary artery bypass graft function during pharmacologic stress. MATERIALS AND METHODS: Aortic and internal mammary artery flow was measured in 11 healthy volunteers by using conventional cine gradient-echo imaging as a reference standard method and turbo-field echo-planar imaging (TFEPI). By using TFEPI, breath-hold flow mapping with a spatial and temporal resolution of 0.8 mm(2) and 23 msec, respectively, can be performed. This sequence was applied in 20 angiographically normal grafts, and total blood flow at rest and during adenosine infusion (140 microgram/kg/min) was measured. RESULTS: Good agreement in aortic and internal mammary artery flow values between conventional fast-field echo and TFEPI techniques was found. The mean bypass graft total flow (+/- SD), as assessed with TFEPI, increased from 30.8 mL/min +/- 13.5 to 76.7 mL/min +/- 36.5 (P <.05) to yield a flow reserve of 2.7. Furthermore, this sequence revealed a difference in total flow between single and sequential grafts at rest (25.4 mL/min vs 40.9 mL/min; P <.05) and during stress (65.2 mL/min vs 98.3 mL/min; P <.05). CONCLUSION: Breath-hold TFEPI provides fast accurate flow measurements with high temporal resolution and allows motion-compensated flow quantification in multiple coronary artery bypass grafts during one 6-minute adenosine infusion.     

Assessment of regional left ventricular long-axis motion with MR velocity mapping in healthy subjects

The pattern of left ventricular long-axis motion during early diastole was assessed with magnetic resonance (MR) velocity mapping in 31 healthy volunteers. Regional long-axis velocity varied with time and position around the ventricle. During systole, the base descended toward the apex. The greatest magnitude of long-axis velocity occurred during early diastole. The lateral wall had the highest velocity (140 mm/sec ± 40 [mean ± standard deviation]); the anterior and inferior walls had lower velocities (96 mm/sec ± 27 and 92 mm/sec ± 34, respectively). The inferoseptal area consistently had the lowest velocities (87 mm/sec ± 40). Absolute values of peak early-diastolic velocity declined with age (r = ?.64, P <.001). Peak early-diastolic velocity was not dependent on heart rate (r =.014, P =.94). Regional variations in left ventricular wall motion were seen. MR velocity mapping is a useful technique for assessing regional left ventricular long-axis heart function.     

Mitral valve flow measured with cine MR velocity mapping in patients with ischemic heart disease: comparison with doppler echocardiography

Diastolic function is an important element of overall left ventricular function. The pattern of flow across the mitral valve is commonly used as a measure of diastolic ventricular function. Magnetic resonance (MR) velocity mapping of blood flow across the mitral valve was compared with Doppler echocardiography. Nineteen patients with known coronary artery disease (mean age. 62 years: 11 with previous myocardial infarction) were studied. The mean value of peak early filling velocity (± standard deviation) was 60.1 cm/sec ± 14.3 with the MR method and 59.4 cm/sec ± 13.7 with echocardiography (P = 0.732). The mean difference between the two measurements (95% confidence interval) was ?0.8 cm/sec (?5.2 cm/sec. +2.2 cm/sec). The mean value of early deceleration was 4.3 mlsec² ± 1.5 with the MR method and 4.0 m/sec² ± 1.5 with echocardiography (P = 0.073). The mean Werence was ?0.4 cm/sec² (?0.92 cm/eec². +0.05 cm/sec²). The mean value of peak atriosystolic velocity was 51 cm/sec ± 14.6 with the MR method and 62 cm/sec ± 17.2 with echocardiography (P = 0.002). The mean difference was ?11 cm/sec (?18.1 cm/sec, ?3.45 cm /sec). Peak atrial filling was consistently lower with the MR method than with echocardiography. Time-averaged measurements of ventricular fflling with MR velocity mapping are an accurate measure of early diastolic filling but underestimate the velocity of atriosystolic fflling.     

Feasibility of aortic pulse pressure and pressure wave velocity MRI measurement in young adults

PURPOSE: To investigate the feasibility of assessing, noninvasively, aortic pulse pressure (APP) and pulse wave velocity (PWV) in the ascending aorta of young adults by means of velocity-encoded magnetic resonance (MR) imaging. MATERIALS AND METHODS: In a series of 11 healthy volunteers, velocity-encoded MR imaging provided pairs of magnitude and phase-contrast images. Blood flow velocity and aortic cross-sectional area (CSA) were determined with a 30-msec temporal resolution. A model analysis revealed that variation in aortic CSA and in maximal blood flow velocity throughout systole could be used to estimate APP and, hence, to derive PWV by means of two different methods. RESULTS: Mean +/- SD values of the APP for the series were 54.2 +/- 16.4 mmHg (range 32.2-84.1 mmHg). The ascending aortic PWV mean +/- SD values were 5.03 +/- 1.10 m/second and 5.37 +/- 1.23 m/second according to the two methods, and both estimates were not significantly different (95% confidence level). CONCLUSION: These results are in agreement with previously published data, suggesting that APP and PWV can be determined, noninvasively, in young adults using MRI.     

Cerebrospinal fluid dynamics and relation with blood flow: a magnetic resonance study with semiautomated cerebrospinal fluid segmentation

RATIONALE AND OBJECTIVES: To investigate and measure temporal and amplitude aspects of blood and cerebrospinal fluid (CSF) flow waveform relations. METHODS: A cine phase-contrast magnetic resonance imaging pulse sequence was used to measure blood and CSF flow in 16 healthy subjects aged 27 +/- 4 years. A semiautomated segmentation algorithm was developed to study CSF flow. RESULTS: Standard deviations of the aqueductal and cervical flow measurements carried out by five observers were 1% and 4%, respectively. The peak systolic arterial flow was 1087 +/- 169 mL/min, and the peak cervical CSF flush (173 +/- 59 mL/min) occurred at 5% +/- 3% of the cardiac cycle after the internal carotid systolic peak flow. Peak aqueductal flush flow (13 +/- 5 mL/min) occurred at 21% +/- 7% of the cardiac cycle after the internal carotid systolic peak flow. CONCLUSIONS: The CSF segmentation algorithm is reproducible. Brain expansion was quickly regulated by a major extracerebral CSF flush flow, whereas ventricular CSF made only a very small contribution.     

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.     

Magnetic resonance evaluation of mitral stenosis

In order to study magnetic resonance (MR) abnormalities in mitral stenosis electrocardiogram (ECG)-gated MR imaging was performed with a 2.0 T MR system in 41 patients with mitral stenosis before catheterization. Mean transverse diameter of the left atrium was 8.9±1.4 cm and anteroposterior diameter was 5.1±1.0 cm, indicating significant enlargement. Homogeneous or inhomogeneous flow-related signals in ventricular diastole were detected in the left atrial cavity in 32 cases (78%), and in the atrial appendage in 35 cases (85%). In 21 patients having a mean wedge pulmonary arterial pressure higher than 20 mm Hg, 20 patients (95%) showed flow-related signals in ventricular diastole. Other MR findings were mitral valve doming in diastole, flow-related signal in the pulmonary artery during systole, and left atrial thrombi.