Speckle Tracking Technique Research Articles

Circulatory Abnormalities in Diastolic Heart Failure

Systolic function in diastolic heart failure (DHF) is defined as the preserved left ventricular (LV) systolic function without LV volume remodelling. However, several studies have reported LV systolic dysfunction in DHF using tissue and pulse Doppler echocardiography and speckle tracking techniques, including our reports on isovolumetric cardiac time interval prolongation in DHF (Table). Recently, some studies have also reported a relationship between arterial stiffness and diastolic dysfunction.

Three-Dimensional Cardiac Strain Imaging in Healthy Children Using RF-Data

In this study, a new radio-frequency (RF)-based, three-dimensional (3-D) strain imaging technique is introduced and applied to 3-D full volume ultrasound data of the heart of healthy children. Continuing advances in performance of transducers for 3-D ultrasound imaging have boosted research on 3-D strain imaging. In general, speckle tracking techniques are used for strain imaging. RF-based strain imaging has the potential to yield better performance than speckle- based methods because of the availability of phase information but such a system output is commercially not available. Furthermore, the relatively low frame rate of 3-D ultrasound data has limited broad application of RF-based cardiac strain imaging. In this study, the previously reported two-dimensional (2-D) strain methodology was extended to the third dimension. Three-dimensional RF-data were acquired in 13 healthy children, in the age range of 6–15 years, at a relatively low frame rate of 38–51 Hz. A 3-D, free-shape, coarse-to-fine displacement and strain estimation algorithm was applied to the RF-data. The heart was segmented using 3-D ellipsoid fitting. Strain was estimated in the radial (R), circumferential (C) and longitudinal directions (L). Our preliminary results reveal the applicability of the 3-D strain estimation technique on full volume 3-D RF-data. The technique enabled 3-D strain imaging of all three strain components. The average strains for all children were in the lateral wall R = 37 ± 10% (infero-lateral) and R = 32% ± 10% (antero-lateral), C = −9% ± 4% (antero-lateral) and C = −9% ± 4% (infero-lateral), L = −18% ± 6 % (antero-lateral) and L = −15% ± 4% (infero-lateral). In the septum, strains were found to be R = 24% ± 10% (antero-septal) and R = 13% ± 5% (infero-septal), C = −13% ± 5% (antero-septal) and −13% ± 5% (infero-septal) and L = −13% ± 3% (antero-septal) and L = −16% ± 5% (infero-septal). Strain in the anterior and inferior walls seemed underestimated, probably caused by the low (in-plane) resolution and poor image quality. The field-of-view as well as image quality were not always sufficient to image the entire left ventricle. It is concluded that 3-D strain imaging using RF-data is feasible, but validation with other modalities and with conventional 3-D speckle tracking techniques will be necessary.

Imaging of Wall Motion Coupled With Blood Flow Velocity in the Heart and Vessels in Vivo: A Feasibility Study

The mechanical property and geometry changes as a result of cardiovascular disease affect both the wall motion and blood flow in the heart and vessels, whereas the latter two are also coupled and therefore continuously influence one another. Simultaneous and registered imaging of both cardiovascular wall motion and blood velocity may thus contribute to more complete computational models of cardiovascular mechanical and fluid dynamics as well as provide additional diagnostic information. The objective of this paper was to determine the feasibility of imaging cardiovascular wall motion coupled with blood flow in vivo. Normal ( n = 6) and infarcted ( n = 5) murine left ventricles, and normal ( n = 5) and aneurysmal ( n = 4) murine abdominal aortas, were imaged in longitudinal views with a 30-MHz ultrasound probe. Using electrocardiogram (ECG) gating, 2-D radio-frequency (RF) data were acquired at a frame rate of 8 kHz. The axial wall velocity and blood velocity were estimated using a speckle-tracking technique. Spatially and temporally registered imaging of both cardiovascular wall motion and blood flow was shown to be feasible. Reduced wall motion was detected in the infarcted region, whereas vortex flow patterns were imaged in diastolic phases of both normal and infarcted left ventricles. The myocardial wall motion and blood flow were found to be more synchronous in the normal heart, where the blood moves toward the anteroseptal wall after the mitral valve opens ( i.e., rapid filling phase), and the anteroseptal wall simultaneously undergoes outward motion. In the infarcted heart, however, in the rapid filling phase, the basal anteroseptal wall starts moving about 20 ms before the mitral valve opens and the blood enters the left ventricle. In the normal aorta, the wall motion and blood velocity were uniform and synchronous. In the aneurysmal aorta, reduced and spatially varied wall motion and vortex flow patterns in the aneurysmal sac were found. The wall motion and blood velocity were thus less synchronous in the aneurysmal aorta. Cardiovascular wall motion and blood flow were both imaged in mice in vivo. This dual information may provide important insights for the diagnosis of cardiovascular disease as well as essential parameters for its biomechanical modeling.

Speckle tracking for the assessment of fetal cardiac function

Speckle tracking for the assessment of fetal cardiac function

Determination of Elastic Properties of Resected Human Breast Tissue Samples Using Optical Coherence Tomographic Elastography

Abstract: The present study is concerned with the application of optical coherence tomographic (OCT) elastography technique for quantitative assessment of the elastic properties of resected human breast tissue samples subjected to axial compressive loading in vitro. Three classes of breast tissue samples, namely normal, benign (fibroadenoma) and malignant (invasive ductal carcinoma), were considered. A speckle tracking technique based on two‐dimensional cross correlation was employed to track the speckle motion between original (pre‐compressed) and the displaced (post‐compressed) OCT images of the tissue samples for the measurement of displacement and strain maps. The overall data reduction approach for quantitative assessment of elastic properties was validated against the results of gelatin phantoms containing activated charcoal particles as scattering centres. Results are presented in the form of OCT images and displacement and axial strain maps for normal, benign and malignant breast tissue samples. Based on the stress–strain relationship obtained for these three classes, the values of stiffness coefficients were reported in terms of modulus of elasticity. Results of the study reveal significant differences between the two‐dimensional displacement vector maps of normal and cancerous breast tissue samples. The stiffness of benign tissue samples is found to be about two times higher than that of normal tissue samples, whereas for malignant samples, it is about four times higher, thereby signifying appreciable differences in the stiffness of cancerous and normal tissue samples.

New Horizons in Doppler Ultrasound Technology: Relevance for Obstetrical Applications

Technologic advances and clinical research have been extending the scope of Doppler sonography and have resulted in the emergence of new diagnostic tools that show significant promise in clinical applications. This article aims to review some of these developments that are relevant for obstetrical practice. One of the major recent technical developments in ultrasound imaging is the ability to assess tissue deformation. This has led to several clinical applications including functional echocardiography that allows evaluation of myocardial function using Doppler and speckle tracking techniques, and sonoelastography, which is ultrasound evaluation of tissue stiffness. Another relevant innovation is power Doppler imaging of regional perfusion. With further critical investigations, these emerging techniques may evolve into useful clinical tools.

Impact of reduced left atrial functions on diagnosis of paroxysmal atrial fibrillation: Results from analysis of time-left atrial volume curve determined by two-dimensional speckle tracking

Atrial fibrillation is commonly associated with impaired reservoir and booster functions of the left atrium (LA). Recent advances in two-dimensional speckle tracking technique (2DST) enabled automatic analysis of the time-LA volume curve representing these functions. Our objective was to evaluate LA function in patients with or without paroxysmal atrial fibrillation (PAF) using 2DST. We studied 111 patients (68 men, age 62 ± 16 years) with (n = 53) or without (n = 58) PAF. After constructing time-LA volume curves from the apical four and two chamber views (iE33, Philips with QLAB 6.0, Philips Medical Systems, Bothell, WA, USA), maximal LA volume (LAVmax), preatrial contraction LA volume (LAVpreA), and minimum LA volume (LAVmin) were obtained. Then, LA reservoir volume (ARV=LAVmax-LAVmin) and active emptying volume (AEV=LAVpreA-LAVmin) were calculated to determine ARV/LAVmax as reservoir function and AEV/LAVpreA as booster pump function. PAF was associated with greater LAVmax than that in controls (80 ± 21 ml versus 65 ± 16 ml, p < 0.001) and with reduced reservoir and booster functions (ARV/LAVmax 46 ± 9% versus 52 ± 7%; AEV/LAVpreA 29 ± 10% versus 36 ± 6%, p < 0.001). Multivariate logistic analysis demonstrated that ARV/LAVmax and AEV/LAVpreA were closely associated with the existence of PAF. These results demonstrate that the present 2DST enables determining LA reservoir and booster functions, providing insights into the diagnosis of PAF.

OC07.03: Learning curve for fetoscopic laser ablation therapy in severe twin–twin transfusion syndrome

Objectives: Twin–twin transfusion syndrome (TTTS) results in significantly altered cardiovascular loading conditions, which may affect both donor and recipient myocardial properties. Myocardial deformation analysis using Vector Velocity Imaging (VVI, Siemens) is an angle independent, speckle-tracking technique used to assess regional cardiac mechanics, which may provide insight into our understanding of myocardial dysfunction in TTTS. Methods: Digital dynamic, two-dimensional four chamber views were interrogated off-line using VVI software. Global longitudinal strain (S%) systolic strain rate (SRs) and diastolic strain rate (SRd) were measured in the left (LV) and right (RV) ventricles of 22 fetal pairs with TTTS and compared to 25 gestational age-matched normal controls. Pulsatility indices (PI) for umbilical (UA) and middle cerebral artery (MCA) were calculated. Results: Gestational age at evaluation was 20.5 ± 1.3 weeks. Donor LV-SRs was higher, while donor RV-SRd was significantly lower than controls (Table 1). Recipient S%, SRs and SRd were significantly lower for both LV and RV in comparison to controls. Donor UA PI was higher than controls (1.93 ± 0.48 vs. 1.41 ± 0.25, P < 0.001) while donor MCA PI was lower (1.47 ± 0.29 vs. 1.87 ± 0.21). Recipient UA and MCA PI were no different than controls. Conclusions: In TTTS, donor mechanics reflect loading conditions. Donor LV systolic function is hyperdynamic, due to hypovolemia and ejection into a low resistance cerebrovascular circuit while the RV ejects into a high resistance placental circuit. Recipient RV and LV are both globally depressed with systolic and diastolic dysfunction despite normal vascular resistances and presumed volume overload, suggesting intrinsic acquired cardiomyopathy.

OC07.02: Fetoscopic laser surgery for twin–twin transfusion syndrome after 26 weeks of gestation

Objectives: Twin–twin transfusion syndrome (TTTS) results in significantly altered cardiovascular loading conditions, which may affect both donor and recipient myocardial properties. Myocardial deformation analysis using Vector Velocity Imaging (VVI, Siemens) is an angle independent, speckle-tracking technique used to assess regional cardiac mechanics, which may provide insight into our understanding of myocardial dysfunction in TTTS. Methods: Digital dynamic, two-dimensional four chamber views were interrogated off-line using VVI software. Global longitudinal strain (S%) systolic strain rate (SRs) and diastolic strain rate (SRd) were measured in the left (LV) and right (RV) ventricles of 22 fetal pairs with TTTS and compared to 25 gestational age-matched normal controls. Pulsatility indices (PI) for umbilical (UA) and middle cerebral artery (MCA) were calculated. Results: Gestational age at evaluation was 20.5 ± 1.3 weeks. Donor LV-SRs was higher, while donor RV-SRd was significantly lower than controls (Table 1). Recipient S%, SRs and SRd were significantly lower for both LV and RV in comparison to controls. Donor UA PI was higher than controls (1.93 ± 0.48 vs. 1.41 ± 0.25, P < 0.001) while donor MCA PI was lower (1.47 ± 0.29 vs. 1.87 ± 0.21). Recipient UA and MCA PI were no different than controls. Conclusions: In TTTS, donor mechanics reflect loading conditions. Donor LV systolic function is hyperdynamic, due to hypovolemia and ejection into a low resistance cerebrovascular circuit while the RV ejects into a high resistance placental circuit. Recipient RV and LV are both globally depressed with systolic and diastolic dysfunction despite normal vascular resistances and presumed volume overload, suggesting intrinsic acquired cardiomyopathy.

Speckle tracking: distinction of physiologic from pathologic LVH?

Speckle tracking: distinction of physiologic from pathologic LVH?

Left Atrial Function: Doppler and Strain

The left atrium modulates left ventricular filling with its reservoir, conduit, and contractile functions. There is growing literature on the importance of a detailed assessment of left atrial function. This review article discusses the echocardiographic assessment of left atrial function by conventional parameters such as atrial size measurements, transmitral and pulmonary Doppler flow, mitral annular tissue velocities, as well as newer techniques such as regional strain and strain rate imaging by color tissue Doppler imaging and two-dimensional speckle tracking techniques. The clinical applications of these techniques in various conditions are discussed.

Comparison between Different Speckle Tracking and Color Tissue Doppler Techniques to Measure Global and Regional Myocardial Deformation in Children

Myocardial deformation parameters obtained by speckle-tracking echocardiography (STE) and color Doppler tissue imaging (CDTI) using two different ultrasound systems and three different software packages were compared. Apical four-chamber, short-axis grayscale, and color Doppler tissue images were prospectively acquired using Vivid 7 and iE33 ultrasound systems in 34 children and then analyzed using EchoPAC and QLAB (STE) and SPEQLE (CDTI). Measurement of myocardial deformation was feasible for all three modalities. Longitudinal strain (epsilon) measurements showed the lowest intraobserver and interobserver variability (intraobserver and interobserver coefficients of variation, 9% and 8% for EchoPAC, 5% and 6% for QLAB, and 14% and 16% for SPEQLE). In addition, longitudinal epsilon had a small bias and narrow limits of agreement when comparing different techniques. The coefficients of variation of circumferential epsilon by EchoPAC and QLAB were 12% and 11% (intraobserver) and 9% and 13% (interobserver), respectively. Circumferential epsilon by STE had a small systematic bias but relatively narrow limits of agreement. The reproducibility of radial epsilon measurements using STE was low, while CDTI epsilon provided better performance (intraobserver and interobserver coefficients of variation for radial posterior epsilon, 12% and 24% for EchoPAC, 39% and 56% for QLAB, and 12% and 14% for SPEQLE). Radial epsilon was on average 50% lower using QLAB compared with EchoPAC and SPEQLE. Systolic strain rate values obtained by STE were lower compared with CDTI-derived values. The limits of agreement for strain rate values among the three modalities were wide, and intraobserver and interobserver variability was poor for all three modalities. Some deformation measurements (e.g., longitudinal and circumferential epsilon) are comparable among different ultrasound machines and software packages, whereas others are significantly different (e.g., radial epsilon and strain rate). This study stresses the need for an industry standard for these techniques.

Dynamic assessment of carotid plaque motion

Assessment of dynamic plaque behaviour may help identify vulnerable carotid plaque before rupture and hence has potential clinical value for screening patients at risk of stroke. The aim of this study was to develop non-invasive ultrasound methods for quantifying dynamic plaque and vessel wall behaviour and assess their potential clinical utility. Ultrasound data from the carotid arteries of one normal subject and four patients with atherosclerotic disease were acquired using a 10 MHz linear array transducer recording raw RF/IQ data at a frame rate up to 80 Hz for 3–6 seconds. Image reconstruction and processing was performed using Matlab. Speckle tracking techniques were developed to characterize: (1) intraplaque deformation; and (2) plaque surface and vessel wall motion. Speckle tracking techniques were able to measure the range of intraplaque tissue deformation (–1.3 to 1.7 mm), plaque surface displacement (0.2–0.7 mm) and vessel wall radial strain (0.02–0.13) throughout the cardiac cycle. The feasibility of using an intraplaque deformation parameter, based on the deformation of a square template, is demonstrated. Speckle tracking techniques can be used to assess dynamic carotid plaque behaviour. Further work is required to evaluate how best to quantify biomechanical behaviour to help predict plaque rupture and hence improve risk stratification models for stroke.

Left atrial asynchrony is a major predictor of 1-year recurrence of atrial fibrillation after electrical cardioversion

The level of atrial mechanical asynchrony may vary within the atrial fibrillation population and this may have pathophysiological relevance. We sought to verify whether the degree of left-atrial mechanical asynchrony associated with atrial fibrillation is a predictor of arrhythmia recurrence after restoration of sinus rhythm with electrical cardioversion. Left atrial volume was calculated, whereas two-dimensional (2D) strain (speckle tracking technique) was used to estimate peak and standard deviation (SD) of time-to-peak of deformation of six segments arbitrarily identified along the perimeter of the cavity, imaged in apical four-chamber view. Left atrial mechanical asynchrony was quantified according to quartiles of time-to-peak SD assuming that larger values would identify higher grades of asynchrony. A total of 130 patients undergoing cardioversion for atrial fibrillation were prospectively enrolled. Time-to-peak SD was inversely related with peak strain (P < 0.001). No differences were observed among groups in terms of clinical, therapeutical and additional echocardiographic variables. At 1-year atrial fibrillation was observed in 53% of patients, with time-to-peak SD linearly related to atrial-fibrillation recurrence (P = 0.014). At multivariate analysis only time-to-peak SD (P = 0.032), but not atrial volume (P = 0.075), was identified as an independent predictor of fibrillation recurrence. This is the first study showing that left atrial asynchrony, quantified as time-to-peak SD of regional atrial strains before electrical cardioversion, is a major independent predictor of fibrillation recurrence in patients back to sinus-rhythm postprocedure.

Torsion of young hearts: a speckle tracking study of normal infants, children, and adolescents

Our aim was to study the rotational mechanics of the heart in a special population including neonates, young children, and adolescents. We showed the effect of age on torsion and the different rotational variables. This study is the first that focuses on neonatal heart mechanics. We recruited 70 normal children between few hours and 18 years old. We excluded abnormal rhythm and function. Short-axis parasternal views were taken at the base of the heart and the apex. Using the speckle tracking technique, we analysed the rotation curves at apex and base and calculated the net twist and torsion of the left ventricle (LV). We also calculated the twist and untwist rates to get the correlation with age and body surface area (BSA). Rotational patterns during diastole also were studied. Deformational time delay between the base and the apex was looked up. Apical rotation and net twist increased with age significantly (r = 0.41 and 0.38, respectively, P = 0.001) but when normalized by LV length there was fixed torsion among age groups. Rotation velocity declined with ageing during systole and diastole for both base and apex (r = -0.58 and -0.62 for twist rate, -0.69 and -0.6 for untwist rate, respectively, P < 0.001). Concordant results were reported for BSA. Deformational delay was decreasing with age (r = -0.74 for systolic and -0.53 for diastolic, P < 0.001). Infants hearts tend to deform more and faster than other groups. While apical twist and net twist increase with age, torsion is fixed among age groups. In young hearts, torsion is the result of differential twist.

Early identification of trastuzumab-related cardiotoxicity with speckle-tracking echocardiography.

e11096 Background: New targeted therapies have improved the prognosis of patients with breast cancer but cause several off-target effects, such as left ventricular dysfunction and heart failure that has still a 5-years mortality of 50%. Adjuvant treatment of breast cancer consists of combination chemotherapy with anthracyclines (A) and, in women with ErbB2 over-expressing disease, trastuzumab (T). A can cause an irreversible left ventricular dysfunction, named type I cardiomyopathy. T causes can cause left ventricular systolic dysfunction between 3% and 18%, and heart failure between 2% and 4%, but these are reversible and there seems to be no apparent ultrastructural changes (II type cardiomyopathy). Methods for measuring cardiac function in M-mode with shortening fraction (FA) and in B-mode with ejection fraction are not very sensitive in detecting early myocardial damage. The aim of this study was to evaluate if myocardial strain by speckle tracking technique (ST) was able to identify early left ventricular dysfunction in mice treated with doxorubicin (D) and T, alone or in combination (D+T). Methods: We measured radial myocardial strain (%) with ST and FA by assessing M-mode short axis projection in C57BL/6 mice at time 0, 2 and 6 days of daily administration of D (2.17 μg/g/day), T (2.25 μg/g/day), D + T (2.17 μg/g/day + 2.25 μg/g/day, respectively), and in a control group. Results: The second day we found a significant reduction of radial strain in the group D (p = 0.003), T (p = 0.03) and D+T (p = 0.003). The FA was reduced significantly on day 2 only in group D (p < 0.001) and D+T (p = 0.001), whereas in group T was normal, and decreased only at day 6 (p = 0.001). Conclusions: With myocardial strain obtained with ST technique it is possible to identify left ventricular systolic dysfunction early, before conventional echocardiography. The reason why this was found only in T group probably lies in the fact that T does not cause myocardial necrosis, in contrast to A, but reversible alterations (harder to detect early with the reduced FA). These studies will be extended to patients, to evaluate the clinical impact of early identification of T-related cardiotoxicity in the treatment of women affected by breast cancer. No significant financial relationships to disclose.

Cardiotoxic effects, or lack thereof, of anti-ErbB2 immunoagents.

e11054 Background: Herceptin (H), an anti-ErbB2 humanized antibody prescribed for treatment of ErbB2-positive breast cancer, has proved to be an essential tool in immunotherapy. However, large-scale clinical studies with H have shown that it engenders cardiomyopathy, particularly in patients treated either concurrently or previously with anthracyclines. Two novel human antitumor immunoconjugates were engineered in our laboratory by fusion of a human anti-ErbB2 scFv, Erbicin, with either a human RNase or the Fc region of a human IgG1, and thus called Erb- hRNase and Erb-hcAb (human anti-ErbB2-compact antibody), respectively. Both immunoagents are selectively cytotoxic for ErbB2-positive cancer cells in vitro and vivo. The Erbicin-derived immunoagents (EDIA) target on breast cancer cells an ErbB2 epitope different from that of H. We report that EDIA did not show in vitro cardiotoxic effects on rat and human cardiomyocytes, whereas H was strongly toxic. Methods: Methods for measuring cardiac function in M-mode with shortening fraction (FA) and in B-mode with ejection fraction are not very sensitive in detecting early myocardial damage. In this study we evaluated myocardial strain by speckle tracking technique (ST) by Color Doppler echocardiography (Visual sonic Vevo 2100) to identify early left ventricular dysfunction in mice treated with EDIA, doxorubicin (D), H, their associations and in a sham group. We measured ST and FA by assessing M-mode short axis projection in C57BL/6 mice at time 0, 2 and 6 days of daily administration. Results: EDIA did not impair cardiac function in vivo in a mouse model whereas H significantly reduced radial strain at 3 days of treatment and fractional shortening (% FS) at 6 days of treatment compared to the sham group in a fashion similar to D. Similarly, cardiac fibrosis, an index of collagen accumulation following cardiac muscle deterioration, was significantly attenuated in mice treated with either Erb-hcAb or Erb-hRNase as compared to those treated with H or D. Conclusions: These results suggest that the Erb-hcAb and the immuno RNase are immunoagents which can fulfil the therapeutic need of patients ineligible to H treatment due to cardiac dysfunction. No significant financial relationships to disclose.

Spatial Heterogeneity of Protein Expression Induced by Dyssynchronous Right Ventricular Pacing in the Left Ventricle of Dogs With Preserved Systolic Function

Background Right ventricular (RV) apical pacing may result in ventricular dyssynchrony, which is associated with functional and morphological changes in the left ventricle (LV). Our aim is to assess contraction and hypertrophy-related protein expression changes in the LV after RV apical pacing. Methods and Results Six dogs underwent dual chamber pacemaker (DDD) implantation and atrioventricular nodal catheter ablation. The pacing group received atria-sensed RV apical pacing for 12 weeks. LV dyssynchrony was assessed with speckle tracking technique. Subsequently, hearts were processed for Western blotting. Four sham-operated dogs were included for comparison. After 12 weeks of RV pacing, cardiac chamber size and LV ejection fraction remained unchanged. Both electrical and mechanical dyssynchrony were evident in RV-paced dogs compared with sham-operated dogs. The late-activated LV lateral wall of paced dogs displayed a 23% reduction in the amount of sarcoplasmic reticulum Ca 2+ ATPase, a 32% reduction in phospholamban levels, but a 3.6-fold increase in phospho-JNK expression, a 2.2-fold increase in phospho-p38, and 1.9-fold increase in phospho-ERK expression. There were no significant differences in the early-activated LV septum between paced and sham dogs. Conclusions Temporal dispersion of mechanical activation by RV apical pacing induced spatial dispersion of protein expression in the LV.

Role of pericardium in the maintenance of left ventricular twist

BackgroundThe role of pericardium in left ventricular (LV) twist has not been directly investigated. We sought to determine the role of pericardium in maintenance of LV twist function in an...

Viscoelastic and Anisotropic Mechanical Properties of in vivo Muscle Tissue Assessed by Supersonic Shear Imaging

The in vivo assessment of the biomechanical properties of the skeletal muscle is a complex issue because the muscle is an anisotropic, viscoelastic and dynamic medium. In this article, these mechanical properties are characterized for the brachialis muscle in vivo using a noninvasive ultrasound-based technique. This supersonic shear imaging technique combines an ultra-fast ultrasonic system and the remote generation of transient mechanical forces into tissue via the radiation force of focused ultrasonic beams. Such an ultrasonic radiation force is induced deep within the muscle by a conventional ultrasonic probe and the resulting shear waves are then imaged with the same probe (5 MHz) at an ultra-fast framerate (up to 5000 frames/s). Local tissue velocity maps are obtained with a conventional speckle tracking technique and provide a full movie of the shear wave propagation through the entire muscle. Shear wave group velocities are then estimated using a time of flight algorithm. This approach provides a complete set of quantitative and in vivo parameters describing the muscle’s mechanical properties as a function of active voluntary contraction as well as passive extension of healthy volunteers. Anisotropic properties are also estimated by tilting the probe head with respects to the main muscular fibers direction. Finally, the dispersion of the shear waves is studied for these different configurations and shear modulus and shear viscosity are quantitatively assessed assuming the viscoelastic Voigt’s model. (E-mail: jl.gennisson@espci.fr)