组织多普勒技术定量评价陈旧性室间隔心肌梗死的右室功能

目的:采用不同组织多普勒技术定量研究陈旧性室间隔心肌梗死患者的右室局部和整体功能。方法:20例陈旧性室间隔心肌梗死患者,30例健康成人。采用应变率及组织速度成像获取右室侧壁各节段的组织速度、位移、应变及应变率曲线。测量收缩功能参数:收缩期峰值速度(Vs)、最大位移(D)、收缩期峰值应变(S)及应变率(SR);测量舒张功能参数:舒张早期充盈速度(Ve)、心房收缩期充盈速度(Va)、舒张早期充盈应变率(Esr)、心房收缩期充盈应变率(Asr)。脉冲组织多普勒获取三尖瓣环运动频谱曲线,计算右室Tei指数。结果:陈旧性室间隔心肌梗死组右室侧壁基底段的S和D以及心尖段的SR和D均较正常组明显减低;基底段及中间段的Ve和Esr均较正常组明显减低;右室Tei指数明显高于正常组。结论:陈旧性室间隔心肌梗死患者右室侧壁多个节段的局部收缩和舒张功能明显受损,此外右室整体功能也明显受损。     

MR velocity mapping of tricuspid flow: Correction for through-plane motion

We evaluated the effect of through-plane motion on tricuspid flow measurements performed with MR velocity mapping in nine normal subjects and 15 patients with possible right ventricular (RV) disease. Eight parameters of RV diastolic function were derived from the tricuspid flow measurements, both before and after a correction for through-plane motion. Measurements of E-peak, A-peak, and time-to-peak filling rate changed significantly after correction for through-plane motion (P < .05). Tricuspid flow as a marker of RV diastolic function should be corrected for the effect of throughplane motion to improve functional evaluation of the RV.     

In vivo time-resolved quantitative motion mapping of the murine myocardium with phase contrast MRI.

Myocardial motion of healthy mice and mice with myocardial infarction was assessed in vivo by phase contrast (PC) cine MRI. The imaging module was a segmented fast low angle shot (FLASH) sequence with velocity compensation in all three gradient directions. To accomplish additional motion encoding, the spin phase was prepared using bipolar gradient pulses, which resulted in a linear dependence between the voxel velocity and spin phase. This method provided accurate quantification of the velocity magnitude and direction of the murine myocardium at a spatial resolution of 234 microm and a temporal resolution of about 10 ms. The acquisition was EKG-gated and the mice were anesthetized by inhalation of 1.5-4.0 vol.% isoflurane at 1.5 l/min oxygen flow. To validate the MRI measurements, an experiment with a calibrated rotating phantom was performed. Deviations between MR velocity measurements and optical assessment by a light detector were lower than 1.6%. During our study, myocardial motion velocities between 0.4 cm/s and 1.7 cm/s were determined for the healthy murine myocardium across the heart cycle. Areas with myocardial infarction were clearly segmented and showed a motion velocity which was significantly reduced. In conclusion, the method is an accurate technique for the assessment of murine myocardial motion in vivo.     

Simultaneous MRI tagging and through-plane velocity quantification: a three-dimensional myocardial motion tracking algorithm

A tracking algorithm was developed for calculation of three-dimensional point-specific myocardial motion. The algorithm was designed for images acquired with simultaneous magnetic resonance imaging (MRI) grid tagging and through-plane velocity quantification. The tagging grid provided the in-plane motion while the velocity quantification measured the through-plane motion. In four healthy volunteers, the in vivo performance was evaluated by comparing the systolic through-plane displacement with the displacement of tagging-grid intersections in long-axis images. The correlation coefficient was 0.93 (P < 0.001, N = 183). A t-test for paired samples revealed a small underestimation of the through-plane displacement by 0.04 +/- 0.09 cm (mean +/- SD, P < 0.001) on an average displacement of 0.77 +/- 0.23 cm toward the apex. The authors conclude that three-dimensional point-specific motion tracking based on simultaneous tagging and velocity quantification is competitive with other methods such as tagging in mutually orthogonal image planes or quantification of three orthogonal velocity components.     

组织多普勒技术对尿毒症患者右室功能的研究

目的:采用不同组织多普勒技术定量研究尿毒症患者右室局部和整体功能。方法:本研究选取20例尿毒症患者,30例健康成人。用应变率成像及组织速度成像获取右室侧壁各节段的组织速度曲线、位移曲线、应变及应变率曲线,脉冲组织多普勒获取三尖瓣环运动频谱曲线。测量局部收缩、舒张功能及整体功能参数。结果:尿毒症组右室侧壁基底段、中段及心尖段的收缩期峰值速度均较正常组增快,基底段的收缩期峰值应变和舒张早期充盈应变率较正常组明显降低。中段心房收缩期充盈速度明显增快,心尖段舒张早期充盈应变率明显降低,心房收缩期充盈速度明显增快。右室Tei指数明显高于正常组,射血时间缩短、等容舒张时间明显延长、舒张早期峰值速度减低、心房收缩期峰值速度增加。结论:尿毒症患者右室整体功能明显受损,右室侧壁多个节段的局部收缩和舒张功能也明显受损。     

Modified Look-Locker inversion recovery (MOLLI) for high-resolution T1 mapping of the heart.

A novel pulse sequence scheme is presented that allows the measurement and mapping of myocardial T1 in vivo on a 1.5 Tesla MR system within a single breath-hold. Two major modifications of conventional Look-Locker (LL) imaging are introduced: 1) selective data acquisition, and 2) merging of data from multiple LL experiments into one data set. Each modified LL inversion recovery (MOLLI) study consisted of three successive LL inversion recovery (IR) experiments with different inversion times. We acquired images in late diastole using a single-shot steady-state free-precession (SSFP) technique, combined with sensitivity encoding to achieve a data acquisition window of < 200 ms duration. We calculated T1 using signal intensities from regions of interest and pixel by pixel. T1 accuracy at different heart rates derived from simulated ECG signals was tested in phantoms. T1 estimates showed small systematic error for T1 values from 191 to 1196 ms. In vivo T1 mapping was performed in two healthy volunteers and in one patient with acute myocardial infarction before and after administration of Gd-DTPA. T1 values for myocardium and noncardiac structures were in good agreement with values available from the literature. The region of infarction was clearly visualized. MOLLI provides high-resolution T1 maps of human myocardium in native and post-contrast situations within a single breath-hold.     

Noninvasive estimation of regional myocardial oxygen consumption by positron emission tomography with carbon-11 acetate in patients with myocardial infarction

We previously demonstrated in experimental studies that myocardial oxygen consumption (MVO2) can be estimated noninvasively with positron emission tomography (PET) from analysis of the myocardial turnover rate constant (k) after administration of carbon-11 (11C) acetate. To determine regional k in healthy human subjects and to estimate alterations in MVO2 accompanying myocardial ischemia, we administered [11C]acetate to five healthy human volunteers and to six patients with myocardial infarction. Extraction of [11C]acetate by the myocardium was avid and clearance from the blood-pool rapid yielding myocardial images of excellent quality. Regional k was homogeneous in myocardium of healthy volunteers (coefficient variation = 11%). In patients, k in regions remote from the area of infarction was not different from values in myocardium of healthy human volunteers (0.061 +/- 0.025 compared with 0.057 +/- 0.008 min-1). In contrast, MVO2 in the center of the infarct region was only 6% of that in remote regions (p less than 0.01). In four patients studied within 48 hr of infarction and again more than seven days after the acute event, regional k and MVO2 did not change. The approach developed should facilitate evaluation of the efficacy of interventions designed to enhance recovery of jeopardized myocardium and permit estimation of regional MVO2 and metabolic reserve underlying cardiac disease of diverse etiologies.     

应用血流向量成像评价AMI患者PCI术前术后左室涡流变化特占

目的：应用血流向量成像（VFM）技术评价急性心肌梗死（AMI）患者经皮冠状动脉介入术（PCI）术前、术后左心室收缩期涡流状态变化。方法：选择健康检查者25例（正常对照组）和AMI患者30例（AMI组）,分别对健康检查者和AMI患者PCI术前、术后1个月行超声心动图检查,采集连续三个心动周期标准三切面彩色血流动态图,分析左心室收缩期涡流横径、纵径、横向、纵向位置及最大向量速度,比较涡流在正常对照组、AMI组术前、术后的变化并进行统计学分析。结果：与正常对照组相比,AMI组术前左心室收缩早期涡流纵径增大[分别为（27．08±4．37）和（21．64±5．41）min,P〈0．05],最大向量速度减小[分别为（25．23±8．42）和（32．83±12．23）cm／s,P〈0．05]。术后1个月AMI组涡流流量、强度、最大向量速度较术前增加（P〈0．05）。结论：健康成人左心室收缩期涡流遵循一定的规律,AMI患者左室收缩期涡流不规则,导致能量的损耗,PCI术后患者的涡流状态有所改善。VFM技术为评价急性心肌梗死患者及PCI术前、术后心腔内血流变化提供了一种新途径。     

Heart motion adapted cine phase-contrast flow measurements through the aortic valve.

A method for magnetic resonance cine velocity mapping through heart valves with adaptation of both slice offset and angulation according to the motion of the valvular plane of the heart is presented. By means of a subtractive labeling technique, basal myocardial markers are obtained and automatically extracted for quantification of heart motion at the valvular level. The captured excursion of the basal plane is used to calculate the slice offset and angulation of each required time frame for cine velocity mapping. Through-plane velocity offsets are corrected by subtracting velocities introduced by basal plane motion from the measured velocities. For evaluation of the method, flow measurements downstream from the aortic valve were performed both with and without slice adaptation in 11 healthy volunteers and in four patients with aortic regurgitation. Maximum through-plane motion at the aortic root level as calculated from the labeled markers averaged 8.9 mm in the volunteers and 6.5 mm in the patients. The left coronary root was visible in 2-4 (mean: 2.2) time frames during early diastole when imaging with a spatially fixed slice. Time frames obtained with slice adaptation did not contain the coronary roots. Motion correction increased the apparent regurgitant volume by 5.7 +/- 0.4 ml for patients with clinical aortic regurgitation, for an increase of approximately 50%. The proposed method provides flow measurements with correction for through-plane motion perpendicular to the aortic root between the valvular annulus and the coronary ostia throughout the cardiac cycle. Magn Reson Med 42:970-978, 1999.     

应变率成像定量评价尿毒症患者右室局部心肌舒张功能

目的:采用应变率成像技术评价尿毒症患者右室局部心肌舒张功能。方法:20例尿毒症患者,30例健康成人。采用应变率成像及组织速度成像获取心尖四腔切面右室侧壁各节段的心肌应变率及多普勒速度曲线,测量曲线上的舒张早期充盈速度(Ve)、心房收缩期充盈速度(Va)、舒张早期充盈应变率(Esr)、心房收缩期充盈应变率(Asr)。结果:尿毒症组右室侧壁基底段的Esr减低,中段Va增快,心尖段Esr减低、Va增快(P<0.05)。结论:尿毒症患者右室侧壁局部心肌存在舒张功能减退。应变率成像联合组织速度成像可检出更多舒张功能受损的右室壁节段。     

3D myocardial tissue tracking with slice followed cine DENSE MRI

PURPOSE: To track three-dimensional (3D) myocardial tissue motion using slice followed cine displacement encoded imaging with stimulated echoes (DENSE). MATERIALS AND METHODS: Slice following (SF) has previously been developed for 2D myocardial tagging to compensate for the effect of through-plane motion on 2D tissue tracking. By incorporating SF into a cine DENSE sequence, and applying displacement encoding in three orthogonal directions, we demonstrate the ability to track discrete elements of a slice of myocardium in 3D as the heart moves through the cardiac cycle. The SF cine DENSE tracking algorithm was validated on a moving phantom, and the effects of through-plane motion on 2D cardiac strain were investigated in six healthy subjects. RESULTS: A through-plane tracking accuracy of 0.46 +/- 0.32 mm was measured for a typical range of myocardial motion using a rotating phantom. In vivo 3D measurements of cardiac motion were consistent with prior myocardial tagging results. Through-plane rotation in a mid-ventricularshort-axis view was shown to decrease the magnitude of the 2D end-systolic circumferential strain by 3.91 +/- 0.43% and increase the corresponding radial strain by 6.01 +/- 1.07%. CONCLUSION: Slice followed cine DENSE provides an accurate method for 3D tissue tracking.     

Altered phosphate metabolism in myocardial infarction: P-31 MR spectroscopy

The high-energy myocardial phosphate metabolism of four patients with acute anterior myocardial infarction after coronary angioplasty and drug therapy was evaluated with cardiac-gated phosphorus magnetic resonance (MR) depth-resolved surface coil spectroscopy (DRESS) 5-9 days after the onset of symptoms. Significant reductions (about threefold) in the phosphocreatine (PCr) to inorganic phosphate (Pi) ratio and elevations in the Pi to adenosine triphosphate (ATP) ratio were observed in endocardially or transmurally derived MR spectra when compared with values from epicardially displaced spectra and values from seven healthy volunteers (P less than .05). High-energy phosphate metabolites and Pi ratios did not vary significantly during the cardiac cycle in healthy volunteers. However, contamination of Pi resonances by phosphomonoester components, including blood 2,3-diphosphoglycerate, precluded accurate spectral quantification of Pi and pH. The results indicate that localized P-31 MR spectroscopy may be used to directly assess cellular energy reserve in clinical myocardial infarction and to evaluate metabolic response to interventions.     

4D phase contrast MRI at 3 T: Effect of standard and blood‐pool contrast agents on SNR,PC‐MRA,and blood flow visualization

Time‐resolved phase contrast (PC) MRI with velocity encoding in three directions (flow‐sensitive four‐dimensional MRI) can be employed to assess three‐dimensional blood flow in the entire aortic lumen within a single measurement. These data can be used not only for the visualization of blood flow but also to derive additional information on vascular geometry with three‐dimensional PC MR angiography (MRA). As PC‐MRA is sensitive to available signal‐to‐noise ratio, standard and novel blood pool contrast agents may help to enhance PC‐MRA image quality. In a group of 30 healthy volunteers, the influence of different contrast agents on vascular signal‐to‐noise ratio, PC‐MRA quality, and subsequent three‐dimensional stream‐line visualization in the thoracic aorta was determined. Flow‐sensitive four‐dimensional MRI data acquired with contrast agent provided significantly improved signal‐to‐noise ratio in magnitude data and noise reduction in velocity data compared to measurements without contrast media. The agreement of three‐dimensional PC‐MRA with reference standard contrast‐enhanced MRA was good for both contrast agents, with improved PC‐MRA performance for blood pool contrast agent, particularly for the smaller supra‐aortic branches. For three‐dimensional flow visualization, a trend toward improved results for the data with contrast agent was observed. Magn Reson Med, 2010. © 2009 Wiley‐Liss, Inc.     

Breathhold time‐resolved three‐directional MR velocity mapping of aortic flow in patients after aortic valve‐sparing surgery

Purpose

To evaluate the utility of breathhold time‐resolved three‐directional MR velocity mapping for quantifying the restoration of normal flow patterns in patients after aortic valve‐sparing surgery.

Materials and Methods

Breathhold time‐resolved three‐directional MR velocity mapping was performed on 13 patients with aortic valve‐sparing surgery. Ten healthy volunteers and 12 patients with ascending aortic aneurysm underwent the same MR examination for comparison. Aortic laminar flow, turbulent flow, and the presence of vortical flow in the sinuses of Valsalva were semiquantitatively assessed and statistically compared between the three groups of subjects.

Results

The average score of laminar flow in the ascending aorta for patients with surgery was not significantly different from that of volunteers (P = 0.210), but was significantly greater than that of patients with aneurysm (P < 0.01). The average score of turbulent flow in patients with surgery was significantly smaller than that of patients with aneurysm (P < 0.01). The presence of systolic vortical flow in the sinuses of Valsalva for patients with surgery was not significantly different from that of healthy volunteers (P = 0.405) and patients with aneurysm (P = 0.238).

Conclusion

Breathhold time‐resolved three‐directional MR velocity mapping allows for quantifying flow patterns in the aortic root and ascending aorta. Normal laminar flow in the ascending aorta and vortical flow in the sinuses of Valsalva can be restored in patients after aortic valve‐sparing surgery. J. Magn. Reson. Imaging 2009;29:569–575. © 2009 Wiley‐Liss, Inc.     

Real-time imaging of skeletal muscle velocity

PURPOSE: To test the feasibility of using real-time phase contrast (PC) magnetic resonance imaging (MRI) to track velocities (1-20 cm/second) of skeletal muscle motion. MATERIALS AND METHODS: To do this we modified a fast real-time spiral PC pulse sequence to accommodate through-plane velocity encoding in the range of -20 to +20 cm/second. We successfully imaged motion of the biceps brachii and triceps brachii muscles during elbow flexion and extension in seven unimpaired adult subjects using real-time PC MRI. RESULTS: The velocity data demonstrate that the biceps brachii and the triceps brachii, antagonistic muscles, move in opposite directions during elbow flexion and extension with velocity values in the muscle tissue ranging from -10 to +10 cm/second. CONCLUSION: With further development, real-time PC MRI may provide a means to analyze muscle function in individuals with neurologic or movement disorders who cannot actively complete the repeated motions required for dynamic MRI techniques, such as cine PC MRI, that are more commonly used in musculoskeletal biomechanics applications.     

Acceleration mapping by fourier acceleration-encoding: in vitro study and initial results in the great thoracic vessels

Acceleration mapping can be conducted by replacing the bipolar gradient pulse of a velocity mapping sequence by a tripolar pulse. However, since the acceleration encoding pulse is longer, the image quality is altered by the requirement of a long echo time. Since Fourier encoding velocity imaging has been shown to be robust, this velocity mapping method was transformed into an acceleration mapping method. Four steps of the tripolar acceleration encoding gradient pulse were applied successively; acceleration was then obtained by Fourier transform after zero-filling. The accuracy of the method was assessed with a phantom giving a pulsatile flow. Acceleration maps of the ascending aorta and pulmonary artery were obtained in 10 healthy volunteers. The acceleration values measured were in the range of known physiologic values. The feasibility of Fourier encoding acceleration imaging was also demonstrated in four patients.     

Variable velocity encoding in a three‐dimensional,three‐directional phase contrast sequence: Evaluation in phantom and volunteers

Purpose:

To evaluate accuracy and noise properties of a novel time‐resolved, three‐dimensional, three‐directional phase contrast sequence with variable velocity encoding (denoted 4D‐vPC) on a 3 Tesla MR system, and to investigate potential benefits and limitations of variable velocity encoding with respect to depicting blood flow patterns.

Materials and Methods:

A 4D PC‐MRI sequence was modified to allow variable velocity encoding (VENC) over the cardiac cycle in all three velocity directions independently. 4D‐PC sequences with constant and variable VENC were compared in a rotating phantom with respect to measured velocities and noise levels. Additionally, comparison of flow patterns in the ascending aorta was performed in six healthy volunteers.

Results:

Phantom measurements showed a linear relationship between velocity noise and velocity encoding. 4D‐vPC MRI presented lower noise levels than 4D‐PC both in phantom and in volunteer measurements, in agreement with theory. Volunteer comparisons revealed more consistent and detailed flow patterns in early diastole for the variable VENC sequences.

Conclusion:

Variable velocity encoding offers reduced noise levels compared with sequences with constant velocity encoding by optimizing the velocity‐to‐noise ratio (VNR) to the hemodynamic properties of the imaged area. Increased VNR ratios could be beneficial for blood flow visualizations of pathology in the cardiac cycle. J. Magn. Reson. Imaging 2012; 36:1450–1459. © 2012 Wiley Periodicals, Inc.     

Radionuclide assessment of right-ventricular involvement in inferior acute myocardial infarction: clinical correlations and in-hospital follow-up

We studied 33 patients (28 males, 5 females) with first inferior acute myocardial infarction (AMI) and 12 normal volunteers. They underwent first-pass (FP) and equilibrium-gated radionuclide angiography (EGRA) within 4 days of the onset of symptoms. The parameters [ejection fraction (EF), peak ejection rate (PER), peak filling rate (PFR)] of the time-activity curve (TAC) of both ventricles [left ventricle (LV), right ventricle (RV)] were computed. The regional wall motion (RWM) was evaluated by parametric images (amplitude and phase). In 43% of the patients with AMI, we found a depressed RVEF, while the LVEF was decreased in only 33%. The sensitivity of diastolic parameters was shown to be clearly superior to that of the systolic parameters (RVPFR, 78%; LVPFR, 79%). The abnormalities of the overall performance of both ventricles were significantly correlated with those of the RWM. The abnormal RVEF allowed us to assess the necrotic involvement of the RV, while a depressed RVPFR suggested an impaired RV compliance mostly on an ischemic basis. Congestive heart failure (CHF) and shock syndrome were significantly correlated with depressed RV parameters, while the LVEF, despite RWM abnormalities, was in the normal range. EGRA with computation of the TAC parameters of both ventricles appeared to be useful for in-hospital prognostic evaluation, therapeutic planning and clinical follow-up of patients with inferior myocardial infarction.     

Radionuclide assessment of right-ventricular involvement in inferior acute myocardial infarction: clinical correlations and in-hospital follow-up

We studied 33 patients (28 males, 5 females) with first inferior acute myocardial infarction (AMI) and 12 normal volunteers. They underwent first-pass (FP) and equilibrium-gated radionuclide angiography (EGRA) within 4 days of the onset of symptoms. The parameters [ejection fraction (EF), peak ejection rate (PER), peak filling rate (PFR)] of the time-activity curve (TAC) of both ventricles [left ventricle (LV), right ventricle (RV)] were computed. The regional wall motion (RWM) was evaluated by parametric images (amplitude and phase). In 43% of the patients with AMI, we found a depressed RVEF, while the LVEF was decreased in only 33%. The sensitivity of diastolic parameters was shown to be clearly superior to that of the systolic parameters (RVPFR, 78%; LVPFR, 79%). The abnormalities of the overall performance of both ventricles were significantly correlated with those of the RWM. The abnormal RVEF allwed us to assess the necrotic involvement of the RV, while a depressed RVPFR suggested an impaired RV compliance mostly on an ischemic basis. Congestive heart failure (CHF) and shock syndrome were significantly correlated with depressed RV parameters, while the LVEF, despite RWM abnormalities, was in the normal range. EGRA with computation of the TAC parameters of both ventricles appeared to be useful for in-hospital prognostic evaluation, therapeutic planning and clinical follow-up of patients with inferior myocardial infarction.     

Myocardial tissue phase mapping with cine phase-contrast mr imaging: regional wall motion analysis in healthy volunteers

PURPOSE: To establish prospectively a database of normal three-dimensional systolic and diastolic endocardial and epicardial velocity values for all myocardial segments in healthy volunteers by using cine phase-contrast velocity magnetic resonance imaging, also called tissue phase mapping (TPM). MATERIALS AND METHODS: The study was approved by the institutional ethics committee and was conducted according to principles of the Declaration of Helsinki; each subject provided informed written consent. Ninety-six healthy volunteers (57 [59%] men, 39 [41%] women; mean age, 38 years +/- 12 [standard deviation]) underwent cardiac phase-contrast imaging with a black blood segmented k-space gradient-echo sequence for the analysis of three-dimensional myocardial velocity with high spatial resolution at 1.5 T on basal, midventricular, and apical short-axis views. Eighteen consecutive volunteers were imaged twice to determine interstudy reproducibility, and intra- and interobserver variability values were analyzed. Systolic and diastolic velocity curves were analyzed for peak velocity and time to peak velocity in the radial, circumferential, and longitudinal directions, as well as for torsion rate and longitudinal strain rate. Mixed-effects models with a random intercept for volunteers were used to test differences among the three ventricular sections and the transmural, endocardial, and epicardial parameters. RESULTS: TPM enabled reproducible assessment of myocardial velocity with small intra- and interobserver variability values. Systolic peak radial velocity was lowest at the apical level (P < .001); diastolic peak radial velocity was similar at all three myocardial levels (P = .73). As viewed from the apex, a relative counterclockwise rotation during systole was followed by a relative clockwise rotation of the apex against the base. Diastolic and systolic peak longitudinal velocity values decreased from base to apex (P < .001). A gradient between endocardium and epicardium was observed for radial velocity values, with greater endocardial velocity values (P < .001). CONCLUSION: TPM is a reproducible comprehensive modality for assessment of regional wall motion, and intra- and interobserver variability values are low.