In vitro evaluation of ultrasound Doppler strain rate imaging: modification for measurement in a slowly moving tissue phantom

Doppler strain rate imaging (SRI) was evaluated in vitro using a silicone strip phantom mimicking slowly moving tissue. A test apparatus was developed that enabled controlled strain experiments with variable strain and strain rate to be performed. SRI strain was measured at eight different calculated strains (range 5.7 to 63.4 %) at three different pump speeds with tissue velocity 0.1, 0.5 and 1.0 mm/s. The effect of varying tissue velocity and strain sample size on the measured SRI strain was elaborated. SRI strains agreed well with calculated values for strain when SRI strain was measured as the average over the whole strip cross-section and the strain sample size was 1.9 mm (mean DIFFERENCE = 2.78%, limits of agreement ± 9.97% for tissue velocity 1.0 mm/s, n = 8). The variance was substantial if single central samples were used, especially for strain sample size of 0.8 mm (mean DIFFERENCE = −7.47%, limits of agreement ± 20.90 for tissue velocity 0.5 mm/s, n = 24). Increasing the strain sample size to 1.9 mm removed some of the underestimation (giving mean difference of −4.46%, n = 24). We found low intra- and interobserver variation. This study indicates that, for the SRI method to give accurate estimates of strain, strain sample size should be in the region of 2 mm. Averaging over several ultrasound (US) beams increased the accuracy further.(E-mail: Knut.Matre@med.uib.no)     

Strain during gastric contractions can be measured using Doppler ultrasonography

This study was undertaken to explore if strain of the muscle layers within the gastric wall could be measured by transabdominal strain rate imaging (SRI), a novel Doppler ultrasound (US) method. A total of 9 healthy fasting subjects (8 women, 1 man; ages 22 to 55 years) were studied and both grey-scale and Doppler US data were acquired with a 5- to 8-MHz linear transducer in cineloops of 97 to 256 frames. Rapid stepwise inflation (5 to 60 mL) of an intragastric bag was carried out and bag pressure and SRI were measured simultaneously. SRI enabled detailed studies of layers within the gastric wall in all subjects. Great variations in strain distribution of the muscle layers were found. Radial strain was much higher in the circular than in the longitudinal muscle layer. Strains derived from SRI correlated well with strains obtained with B-mode measurements (r = 0.98, p < 0.05). During balloon distension, we found an inverse correlation between pressure and radial strain (r = -0.87, p < 0.05). Intraobserver correlation of strain estimation was r = 0.98 (p < 0.05) and intraobserver agreement was 0.2% +/- 18.6% (mean difference +/- 2SD, % strain). Interobserver correlation was r = 0.84 (p < 0.05) and interobserver agreement was 6.9% +/- 56.8%. SRI enables detailed mapping of radial strain distribution of the gastric wall and correlates well with B-mode measurements and pressure increments.     

In-vivo validation of a new clinical tool to quantify three-dimensional myocardial strain using ultrasound

Three-dimensional (3D) strain analysis based on real-time 3-D echocardiography (RT3DE) has emerged as a novel technique to quantify regional myocardial function. The goal of this study was to evaluate accuracy of a novel model-based 3D tracking tool (eSie Volume Mechanics, Siemens Ultrasound, Mountain View, CA, USA) using sonomicrometry as an independent measure of cardiac deformation. Thirteen sheep were instrumented with microcrystals sutured to the epi- and endocardium of the inferolateral left ventricular wall to trace myocardial deformation along its three directional axes of motion. Paired acquisitions of RT3DE and sonomicrometry were made at baseline, during inotropic modulation and during myocardial ischemia. Accuracy of 3D strain measurements was quantified and expressed as level of agreement with sonomicrometry using linear regression and Bland–Altman analysis. Correlations between 3D strain analysis and sonomicrometry were good for longitudinal and circumferential strain components (r?=?0.78 and r?=?0.71) but poor for radial strain (r?=?0.30). Accordingly, agreement (bias?±?2SD) was ?5?±?6?% for longitudinal, ?5?±?7?% for circumferential, and 15?±?19?% for radial strain. Intra-observer variability was low for all components (intra-class correlation coefficients (ICC) of respectively 0.89, 0.88 and 0.95) while inter-observer variability was higher, in particular for radial strain (ICC?=?0.41). The present study shows that 3D strain analysis provided good estimates of circumferential and longitudinal strain, while estimates of radial strain were less accurate between observers.     

Experimental assessment of a new research tool for the estimation of two-dimensional myocardial strain

One-dimensional strain imaging has been shown to be angle dependent. To address this problem, a new methodology, 2D-strain, has become available. The aim of this study was to validate this methodology in an in vivo set-up against sonomicrometry. In five open chest sheep, ultrasound gray-scale images were acquired of the inferolateral wall from two different angles. The longitudinal and radial strain components were simultaneously extracted using the novel 2D-strain methodology. The extracted values were compared with sonomicrometry using Bland-Altman statistics and correlation coefficients. A good agreement was found for the longitudinal strain component, while, for the radial strain estimates, the accuracy was less. 2D-strain is a fast and accurate tool to assess longitudinal strain from apical views. Further improvements are needed for the method to be sufficiently accurate in estimating the deformation perpendicular or close to perpendicular to the ultrasound beam.     

长轴方向应变和应变率成像影响因素分析

目的探讨室壁与入射超声之间的夹角及应变长度（SL）对长轴方向应变成像（SI）和应变率成像（SRI）的影响。方法SRI定量分析模式下，取样容积置于健康人和冠心病患者心尖四腔观后间隔中部，SL分别设置为2mm、12mm和20mm，测量收缩期和舒张早期峰值应变率（SRs和SRe），比较不同SL条件下所测SRs和SRe有无差异。SI模式下心尖长轴观定性观察健康人、冠心病和扩张性心肌病患者左室各节段的彩色分布；改变成像角度，定性观察室壁彩色变化。结果SL改变时SRs和SRe显著变化，SRI二维图像与曲线质量亦发生变化；由于角度的影响，健康人、冠心病和扩张性心肌病患者均有反相应变节段，改变成像角度，室壁彩色分布亦发生变化。结论SI和SRI受角度和应变长度影响，实际应用中应注意切面和取样部位的选择及仪器的设置。     

Effects of simultaneous application of ultrasound and microbubbles on intracerebral hemorrhage in an animal model

Microbubble-enhanced sonothrombolysis (MEST) may be an alternative therapeutic option in ischemic stroke. Clinical study of the efficacy of MEST as an adjunct stroke therapy, before imaging with CT or MRI, requires experimental data on the safety of this approach in the presence of hemorrhagic stroke. We, therefore, investigated the effect of diagnostic transcranial ultrasound combined with microbubbles (US + MB) in an experimental animal model of intracerebral hemorrhage (ICH). ICH was induced in anesthetized rats by intracerebral collagenase injection. Transcranial ultrasound (2 MHz, mechanical index 1.3, 1051 kPa) was applied 3 h after ICH induction to rat brains for 30 min during a continuous IV infusion of sulfur hexafluoride microbubbles (SonoVue). The size of cerebral hemorrhage, the extent of brain edema, and the amount of apoptosis were compared with those from control rats with ICH but without US + MB. Results showed no significant effect of US + MB on hemorrhage size (control 23.3 +/- 10.7 mm(3), US + MB 20.3 +/- 5.8 mm(3)), on the extent of brain edema (control 3.3 +/- 2.0%, US +MB 3.5 +/- 1.9%), or on the rate of apoptosis (control 5.2 +/- 1.5%, US + MB 5.2 +/- 1.0%). We conclude that diagnostic ultrasound in combination with microbubbles does not cause additional damage to the rat brain during ICH in our experimental set-up. This finding provides support for the use of MEST as an early stroke therapy.     

Quantifying myocardial deformation throughout the cardiac cycle: a comparison of ultrasound strain rate, grey-scale M-mode and magnetic resonance imaging

Strain rate imaging (SRI) is a new ultrasound (US) approach to the quantification of regional myocardial deformation. It previously has been validated in vitro and in vivo against other imaging techniques. However, in all such studies, only peak strain values were compared, and the temporal evolution of the strain curve was not studied. Yet, it is the temporal evolution of the strain curves that contains the more important clinical information (e.g., asynchrony, viability, etc). Thus, the aim of this study was to compare the evolution of strain during the complete cardiac cycle as measured by US SRI, US grey-scale M-mode and magnetic resonance imaging (MRI). In 10 healthy volunteers and 20 patients with chronic ischaemic heart disease, radial deformation of the inferolateral segment of the left ventricle was measured by US SRI, US M-mode and MRI. The correspondence of the temporal characteristics of these strain curves were compared by defining an intraclass correlation coefficient (ICC). In healthy volunteers, an overall good agreement (mean ICC: 0.75 and 0.63 for systole and diastole) was found between the different methods. However, in patients with abnormal segmental deformation and low peak strain values, the agreement was less (mean ICC: 0.42 and 0.32), but remained within acceptable limits for clinical decision making. Myocardial deformation measurements using SRI correlated well with MRI and US M-mode measurements throughout the complete cardiac cycle.     

纵向、径向及周向二维应变评价冠心病患者左心室局部收缩功能异常

目的 应用二维应变超声心动图定量分析静息状态下冠心病患者局部心肌纵向、径向及周向的收缩期峰值应变,了解静息状态下冠状动脉狭窄对左室局部心肌收缩功能的影响.方法 26例冠心病患者和26例健康志愿者接受超声检查,获取心尖四腔观、二腔观及左心长轴观和左室短轴观(二尖瓣环、乳头肌和心尖水平)二维灰阶图像,分析各个心肌节段的纵向、径向和周向的收缩期峰值应变.按左室18节段划分法,将26例冠心病患者的共194个病变心肌节段按供血冠脉狭窄程度分为两组:A组为冠脉狭窄≤70%供血的心肌,B组为冠脉狭窄>70%供血的心肌.结果 A组共90个节段.其纵向收缩期峰值应变(SL)明显低于对照组(P<0.05),而径向收缩期峰值应变(SR)和周向收缩期峰值应变(SC)低于对照组,但差异无统计学意义(P>0.05);B组共104个节段,其SL、SR和SC均明显低于对照组(P<0.05),A组和B组之间SL、SC和SR的差异有统计学意义(P<0.05).结论 二维应变超声心动图能准确评价冠心病患者左室局部收缩功能异常,局部心肌SL、SR和SC的变化町反映冠脉狭窄严重程度.     

Pulsed ultrasound and neoplastic transformation in vitro

C3H/10T1/2 mouse embryo fibroblast cells grown as 1.2 cm diameter monolayers were assayed for cytotoxicity and neoplastic transformation following 30 min insonations with three types of pulsed ultrasound (US). Two of the US beams, with a repetition frequency of 1 kHz, center frequencies of 2.5 and 3.5 MHz and time-averaged intensities (ITA) of 31 and 6.7 mW/cm2, respectively, simulated biomedical pulse-echo imaging. The third US beam, with a repetition frequency of 5 kHz, center frequency of 2.5 MHz and ITA of 885 mW/cm2, simulated pulsed biomedical Doppler insonation. All three US beams exhibited negative pressure amplitudes in the range of 1 MPa over the cellular preparation. In order to provide uniform insonation for all exposed cells, all beams were unfocused; pressure amplitude variations did not exceed +/- 15% within a beam diameter of at least 1.5 cm, within which test samples of attached cells were confined. Ultrasound was delivered alone or in combination with x-rays (2 Gy, 240 kVp at 3.5 Gy/min given within 5 min before US) as a costressor. Under all treatment conditions, there was no significant affect of US on clonogenic survival or neoplastic transformation (cumulative probabilities ranging from 0.13 to 0.92).     

Effects of fascia lata on HIFU lesioning in vitro

The effects of fascia lata on high intensity focused ultrasound (US), or HIFU,-induced lesions were demonstrated through comparison with and without fascia lata in bovine thigh muscle tissue. Experiments were conducted in an arrangement with a three-way multiscan ultrasonic inspection system and imaging done by B-mode US. Bovine thigh muscle (8-cm thick) was treated with 1.5 MHz for 8 s. Spatial peak intensity (ISP) was 3000 W/cm2. B-mode US imaging detected appearance at the HIFU treatment site. At a free-field intensity of 4000 W/cm2, the observed lesion length (along the axis) with fascia lata was 12 +/- 1.82 mm, compared with 4 +/- 1.54 mm for samples without fascia lata. At 3000 W/cm2, the values for samples with fascia lata and samples without fascia lata, respectively, were 13 +/- 1.50 mm and 2 +/- 1.42 mm. During a 30-s exposure, at ISP of 2000 W/cm2, the peak temperature reached 41 degrees C in samples without fascia lata and 70 degrees C in samples with fascia lata. At ISP of 3000 and 4000 W/cm2, the peak temperature reached, respectively, 73 degrees C and 84 degrees C in samples without fascia lata, compared with 102 degrees C and 104 degrees C, respectively, for samples with fascia lata. The results confirm that fascia lata contributes to increasing tissue necrosis, temperature elevation and echogenicity in US images.     

左室径向应变和圆周应变对冠状动脉粥样硬化性心脏病患者心肌缺血的诊断价值

目的 应用斑点追踪技术评价室壁运动正常的心肌缺血患者左室径向应变及圆周应变,探讨其检测心肌缺血的临床价值.方法 30例经冠状动脉造影证实的冠状动脉粥样硬化性心脏病（CHD）患者,28例健康者为对照组,应用二维应变软件分析左室短轴二尖瓣水平、乳头肌水平及心尖水平图像,获取左室短轴各节段心肌径向应变和圆周应变均值.结果 CHD组径向应变和圆周应变均较对照组减低（P〈0.001）;ROC曲线表明径向应变诊断心肌缺血的敏感性为89.3%,特异性为80.0%;圆周应变诊断心肌缺血的敏感性为75.0%,特异性为63.3%;径向应变诊断心肌缺血的敏感性和特异性均较圆周应变增高.结论 二维短轴应变能较敏感地发现心肌缺血,径向应变较圆周应变能更准确地评价心肌缺血.     

A maximum likelihood approach to diffeomorphic speckle tracking for 3D strain estimation in echocardiography

The strain and strain-rate measures are commonly used for the analysis and assessment of regional myocardial function. In echocardiography (EC), the strain analysis became possible using Tissue Doppler Imaging (TDI). Unfortunately, this modality shows an important limitation: the angle between the myocardial movement and the ultrasound beam should be small to provide reliable measures. This constraint makes it difficult to provide strain measures of the entire myocardium. Alternative non-Doppler techniques such as Speckle Tracking (ST) can provide strain measures without angle constraints. However, the spatial resolution and the noisy appearance of speckle still make the strain estimation a challenging task in EC. Several maximum likelihood approaches have been proposed to statistically characterize the behavior of speckle, which results in a better performance of speckle tracking. However, those models do not consider common transformations to achieve the final B-mode image (e.g. interpolation). This paper proposes a new maximum likelihood approach for speckle tracking which effectively characterizes speckle of the final B-mode image. Its formulation provides a diffeomorphic scheme than can be efficiently optimized with a second-order method. The novelty of the method is threefold: First, the statistical characterization of speckle generalizes conventional speckle models (Rayleigh, Nakagami and Gamma) to a more versatile model for real data. Second, the formulation includes local correlation to increase the efficiency of frame-to-frame speckle tracking. Third, a probabilistic myocardial tissue characterization is used to automatically identify more reliable myocardial motions. The accuracy and agreement assessment was evaluated on a set of 16 synthetic image sequences for three different scenarios: normal, acute ischemia and acute dyssynchrony. The proposed method was compared to six speckle tracking methods. Results revealed that the proposed method is the most accurate method to measure the motion and strain with an average median motion error of 0.42 mm and a median strain error of 2.0 ± 0.9%, 2.1 ± 1.3% and 7.1 ± 4.9% for circumferential, longitudinal and radial strain respectively. It also showed its capability to identify abnormal segments with reduced cardiac function and timing differences for the dyssynchrony cases. These results indicate that the proposed diffeomorphic speckle tracking method provides robust and accurate motion and strain estimation.     

Apparatus for ultrasound tissue characterization of excised specimens

Apparatus is described for measurement of sound speed and ultrasound attenuation coefficients by the substitution technique in the frequency range 3 to 8 MHz. Phase-cancellation artifacts leading to overestimation of attenuation coefficients are avoided by use of an acoustoelectric transducer. Specimens confined by polystyrene windows can be interrogated by focused ultrasound beams at selected locations spaced on a grid of 3 x 3 mm voxels. Pulse time of flight is measured with an accuracy of 30 ns, yielding sound speeds accurate to +/- 6.7 m/s, for samples 10 mm thick. Uncertainties in measured insertion losses range from 0.1 dB in low-loss (10 dB) specimens to 0.5 dB in high-loss (25 dB) specimens.     

High frequency ultrasound imaging detects cardiac dyssynchrony in noninfarcted regions of the murine left ventricle late after reperfused myocardial infarction

Cardiac dyssynchrony in the left ventricles of murine hearts late (> or =28 d) after reperfused myocardial infarction (post-MI) was assessed using high frequency 30 MHz B-mode ultrasound imaging. Nine post-MI and six normal C57Bl/6 mice were studied in both short- and long-axis views. Regional time to peak displacement (T(peak_d)) and time to peak strain (T(peak_s)) were calculated in 36 sectors along the myocardial circumference; then their standard deviations (SD_T(peak_d) and SD_T(peak_s)) were computed among noninfarcted myocardial regions for each mouse and were compared between the normal and post-MI mouse groups with Student's t-test. The comparison revealed that SD_T(peak_d) and SD_T(peak_s) were significantly larger in the post-MI hearts than in the normal hearts. The displacement uniformity ratio was determined to be 0.97 +/- 0.01 and 0.85 +/- 0.07 for radial and circumferential displacements in the normal hearts, respectively; and 0.59 +/- 0.17 and 0.64 +/- 0.24 in the post-MI hearts. In conclusion, this high resolution ultrasound image tracking method provides for the detection of cardiac dyssynchrony in the noninfarcted regions in the murine left ventricles late after MI by identifying the temporal and spatial disparity of regional myocardial contraction.     

Cardiac motion and strain detection using 4D CT images: comparison with tagged MRI,and echocardiography

Ischemic heart disease is a leading cause of death in the modern world. Coronary obstruction is the basis for ischemic heart disease and leads to decreased cardiac supply and decreased contractility of the myocardium. Recently, high quality 4D computed tomography (CT) has become available for cardiac imaging and provides the clinician with high quality anatomical images. In this article, a new method is proposed to detect 3D motion and strain from 4D cardiac CT images by constraining intensity constancy, myocardial volume changes and motion smoothness assumptions. The proposed method is validated by using manual tracking of the cardiac CT landmarks. The average error for the manual tracking, by an expert, was 2.9 ± 0.9 mm. As an additional validation, the cardiac CT strain values were compared to the cardiac tagged magnetic resonance imaging (MRI) and 2D B-mode echocardiography strain values of the same patients. The correlation ratio was significantly high for CT and tagged MRI radial strain values (r = 0.76, 95 % confidence interval, P < 0.001). The correlation ratio was meaningful for CT and echocardiography radial strain values as well (r = 0.67, 95 % confidence interval, P < 0.001). The correlation ratio for CT and tagged MRI circumferential strain values was acceptable (r = 0.73, 95 % confidence interval, P < 0.001), while the correlation ratio for CT and echocardiography circumferential strain values was good as well (r = 0.61, 95 % confidence interval, P < 0.001). In general, motion and strain values computed from cardiac CT images agree with motion and strain values computed from tagged MRI and echocardiography images.     

Estimation of myocardial strain from non-rigid registration and highly accelerated cine CMR

Sparsely sampled cardiac cine accelerated acquisitions show promise for faster evaluation of left-ventricular function. Myocardial strain estimation using image feature tracking methods is also becoming widespread. However, it is not known whether highly accelerated acquisitions also provide reliable feature tracking strain estimates. Twenty patients and twenty healthy volunteers were imaged with conventional 14-beat/slice cine acquisition (STD), 4× accelerated 4-beat/slice acquisition with iterative reconstruction (R4), and a 9.2× accelerated 2-beat/slice real-time acquisition with sparse sampling and iterative reconstruction (R9.2). Radial and circumferential strains were calculated using non-rigid registration in the mid-ventricle short-axis slice and inter-observer errors were evaluated. Consistency was assessed using intra-class correlation coefficients (ICC) and bias with Bland–Altman analysis. Peak circumferential strain magnitude was highly consistent between STD and R4 and R9.2 (ICC?=?0.876 and 0.884, respectively). Average bias was ?1.7?±?2.0?%, p?<?0.001, for R4 and ?2.7?±?1.9?%, p?<?0.001 for R9.2. Peak radial strain was also highly consistent (ICC?=?0.829 and 0.785, respectively), with average bias ?11.2?±?18.4?%, p?<?0.001, for R4 and ?15.0?±?21.2?%, p?<?0.001 for R9.2. STD circumferential strain could be predicted by linear regression from R9.2 with an R² of 0.82 and a root mean squared error of 1.8?%. Similarly, radial strain could be predicted with an R² of 0.67 and a root mean squared error of 21.3?%. Inter-observer errors were not significantly different between methods, except for peak circumferential strain R9.2 (1.1?±?1.9?%) versus STD (0.3?±?1.0?%), p?=?0.011. Although small systematic differences were observed in strain, these were highly consistent with standard acquisitions, suggesting that accelerated myocardial strain is feasible and reliable in patients who require short acquisition durations.     

Non-invasive Vascular Radial/Circumferential Strain Imaging and Wall Shear Rate Estimation Using Video Images of Diagnostic Ultrasound

The aim of this work was to develop a convenient method for radial/circumferential strain imaging and shear rate estimation that could be used as a supplement to the current routine screening for carotid atherosclerosis using video images of diagnostic ultrasound. A reflection model-based correction for gray-scale non-uniform distribution was applied to B-mode video images before strain estimation to improve the accuracy of radial/circumferential strain imaging when applied to vessel transverse cross sections. The incremental and cumulative radial/circumferential strain images can then be calculated based on the displacement field between consecutive B-mode images. Finally, the transverse Doppler spectra acquired at different depths along the vessel diameter were used to construct the spatially matched instantaneous wall shear values in a cardiac cycle. Vessel phantom simulation results revealed that the signal-to-noise ratio and contrast-to-noise ratio of the radial and circumferential strain images were increased by 2.8 and 5.9 dB and by 2.3 and 4.4 dB, respectively, after non-uniform correction. Preliminary results for 17 patients indicated that the accuracy of radial/circumferential strain images was improved in the lateral direction after non-uniform correction. The peak-to-peak value of incremental strain and the maximum cumulative strain for calcified plaques are evidently lower than those for other plaque types, and the echolucent plaques had higher values, on average, than the mixed plaques. Moreover, low oscillating wall shear rate values, found near the plaque and stenosis regions, are closely related to plaque formation. In conclusion, the method described can provide additional valuable results as a supplement to the current routine ultrasound examination for carotid atherosclerosis and, therefore, has significant potential as a feasible screening method for atherosclerosis diagnosis in the future.     

Feasibility and reliability of strain and strain rate measurement in neonates by optimizing the analysis parameters settings

The optimal combination of region-of-interest (ROI) size and strain length (SL) allowing two-segment strain and strain rate analyses in term neonates was investigated. The impact of different ROI sizes and SLs on the strain and strain rate beat-to-beat variation (BBV) was assessed in 80 good-quality tissue velocity images. Both BBVs decreased with increased ROI length and with increased SL (p < 0.05). There were no significant differences in the BBVs for ROI width 2, 3 and 4 mm (p > 0.05). Among the combinations eligible for two segment analysis, the lowest BBVs were found using SL 10 mm, ROI length 1 mm and ROI width 3 mm. Using this combination, the mean difference between the single-cycle value and two-cycle compound value for peak systolic strain rate was 6.2%, peak systolic strain was 2.9% and end systolic strain was 3.2% of the two-cycle compound mean values. Hence, strain and strain rate measurement in tissue velocity images in neonates is feasible and reliable.     

组织多普勒径向应变率的理解误区及其局限性

目的 明确组织多普勒成像技术(TDI)的径向应变率(SR)与心肌速度梯度(MVG)的异同,分析左心室径向SR在临床应用的局限.方法 检索有关SR及MVG的资料.获取30例健康志愿者(正常组)及30例原发性高血压患者(高血压组)左心室短轴前室间隔及左心室后壁径向SR曲线.比较两组左心室后壁收缩期(SRs)及舒张早期(Sre)峰值径向SR的差异.分别采用应变长度(SL)为12 mm及8 mm,测量正常组左心室后壁SRs及Sre峰值径向SR.结果 正常组左心室后壁的径向SR曲线比较规律,而前室间隔的径向SR曲线比较杂乱.正常组左心室后壁Sre明显大于SRs(5.21±0.94) 1/s vs (2.08±0.31) 1/s(P＜0.05).高血压组左心室后壁径向SRs及Sre均低于正常组(1.13±0.29)1/s vs (2.08±0.31) 1/s、(2.45±0.52)1/svs (5.21±0.94) 1/s(P＜0.05).正常组SL＝12 mm时的SRs略大于SL=8 mm时的测值但差异无统计学意义(1.83±0.27)1/s vs (2.08±0.31)1/s(P＞0.05);而SL=12mm的Sre明显大于SL=8 mm时的测值(4.29±0.70) 1/s vs(5.21±0.94) 1/s(P＜0.05).结论 组织多普勒径向SR并不完全等同于MVG,在评价左心室短轴局部心功能时有一定的局限性.     

Assessment of regional long-axis function during dobutamine echocardiography

Echocardiographic analysis of regional left ventricular function is based upon the assessment of radial motion. Long-axis motion is an important contributor to overall function, but has been difficult to evaluate clinically until the recent development of tissue Doppler techniques. We sought to compare the standard visual assessment of radial motion with quantitative tissue Doppler measurement of peak systolic velocity, timing and strain rate (SRI) in 104 patients with known or suspected coronary artery disease undergoing dobutamine stress echocardiography (DbE). A standard DbE protocol was used with colour tissue Doppler images acquired in digital ciné-loop format. Peak systolic velocity (PSV), time to peak velocity (TPV) and SRI were assessed off-line by an independent operator. Wall motion was assessed by an experienced reader. Mean PSV, TPV and SRI values were compared with wall motion and the presence of coronary artery disease by angiography. A further analysis included assessing the extent of jeopardized myocardium by comparing average values of PSV, TPV and SRI against the previously validated angiographic score. Segments identified as having normal and abnormal radial wall motion showed significant differences in mean PSV (7.9 +/- 3.8 and 5.9 +/- 3.3 cm/s respectively; P < 0.001), TPV (84 +/- 40 and 95 +/- 48 ms respectively; P = 0.005) and SRI (-1.45 +/- 0.5 and -1.1 +/- 0.9 s(-1) respectively; P < 0.001). The presence of a stenosed subtending coronary artery was also associated with significant differences from normally perfused segments for mean PSV (8.1+/-3.4 compared with 5.7+/-3.7 cm/s; P < 0.001), TPV (78 +/- 50 compared with 92 +/- 45 ms; P < 0.001) and SRI (-1.35 +/- 0.5 compared with -1.20 +/- 0.4 s(-1); P = 0.05). PSV, TPV and SRI also varied significantly according to the extent of jeopardized myocardium within a vascular territory. These results suggest that peak systolic velocity, timing of contraction and SRI reflect the underlying physiological characteristics of the regional myocardium during DbE, and may potentially allow objective analysis of wall motion.