Clément Papadacci

French Institute of Health and Medical Research | Inserm

In biological tissue, an increase in elasticity is often a marker of abnormalities. Techniques such as quasi-static ultrasound elastography have been developed to assess the strain distribution in soft tissues in two dimensions using a quasi-static compression. However, as abnormalities can exhibit very heterogeneous shapes, a three dimensional app...

Background: Ultrasound localization microscopy (ULM) based on ultrafast ultrasound imaging of circulating microbubbles (MB) can image microvascular blood flows in vivo up to the micron scale. Takayasu arteritis (TA) has an increased vascularisation of the thickened arterial wall when active. We aimed to perform vasa vasorum ULM of the carotid wall...

Objective Early diagnosis and acute knowledge of cerebral disease require to map the microflows of the whole brain. Recently, ultrasound localization microscopy (ULM) was applied to map and quantify blood microflows in 2D in the brain of adult patients down to the micron scale. Whole brain 3D clinical ULM remains challenging due to the transcranial...

Background Heart transplantation is the definitive treatment for many cardiovascular diseases. However, no ideal approach is established to evaluate heart grafts and it mostly relies on qualitative interpretation of surgeon based on the organ aspect including anatomy, color and manual palpation. In this study we propose to assess quantitatively the...

Background Non-invasive high-resolution imaging of the cerebral vascular anatomy and function is key for the study of intracranial aneurysms, stenosis, arteriovenous malformations, and stroke, but also neurological pathologies, such as degenerative diseases. Direct visualization of the microvascular networks in the whole brain remains however chall...

Objectives The purpose of this study was to demonstrate 3-dimensional (3D) coronary ultrasound localization microscopy (CorULM) of the whole heart beyond the acoustic diffraction limit (<20 μm resolution) at ultrafast frame rate (>1000 images/s). Background Direct assessment of the coronary microcirculation has long been hampered by the limited sp...

Mapping blood microflows of the whole brain is crucial for early diagnosis of cerebral diseases. Ultrasound localization microscopy (ULM) was recently applied to map and quantify blood microflows in 2D in the brain of adult patients down to the micron scale. Whole brain 3D clinical ULM remains challenging due to the transcranial energy loss which s...

Quantitative assessment of myocardial stiffness is crucial to understand and evaluate cardiac biomechanics and function. Despite the recent progresses of ultrasonic shear wave elastography, quantitative evaluation of myocardial stiffness still remains a challenge because of strong elastic anisotropy. In this paper we introduce a smart ultrasound ap...

Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): Bettencourt Foundation Background/Introduction We demonstrated recently that Ultrafast ultrasound Doppler imaging can image the intramyocardial coronary circulation in beating hearts of large animals and patients [1]. Yet, ultrasound spatial resolution remains lim...

Funding Acknowledgements Type of funding sources: Public grant(s) – EU funding. Main funding source(s): ERC Introduction Myocardial stiffness (MS) is crucial to understand cardiac biomechanics and evaluate cardiac function. We recently demonstrated that shear wave imaging using acoustic radiation force can provide quantitative end-diastolic MS in...

The objectives were to develop a novel three-dimensional technology for imaging naturally occurring shear wave (SW) propagation, demonstrate feasibility on human volunteers and quantify SW velocity in different propagation directions. Imaging of natural SWs generated by valve closures has emerged to obtain a direct measurement of cardiac stiffness....

The objectives were to develop a novel three-dimensional technology for imaging naturally occurring shear wave (SW) propagation, demonstrate feasibility on human volunteers and quantify SW velocity in different propagation directions. Imaging of natural SWs generated by valve closures has emerged to obtain a direct measurement of cardiac stiffness....

Funding Acknowledgements European Research Council under the European Union’s Seventh Framework Programme (FP/2007-2013) / ERC Grant Agreement n° 311025 and the ANR-10-IDEX-00 Background 4D echocardiography has the strong potential to improve cardiac index quantification by providing reproducible and user independent measurements. Quantification of...

Ultrasound techniques currently used in echocardiography are limited by conventional frame rates. Ultrafast ultrasound imaging is able to capture images at frame rates up to 100 times faster compared with conventional imaging. Specific applications of this technology have been developed and tested for clinical use in pediatric and adult cardiac ima...

Multi-plane-transmit (MPT) is a matrix array based 3D beamforming methodology, which combines the features of diverging wave compounding (DWC) and multi-line-transmit (MLT). The MPT beams are diverging in one lateral dimension, while focused in the other lateral dimension, leading to a plane-wise reconstruction process. As a result, compounding is...

Objectives The goal of this study was to demonstrate the feasibility of semi-automatic evaluation of cardiac Doppler indices in a single heartbeat on human hearts by performing 4D ultrafast echocardiography with a dedicated sequence of 4D simultaneous tissue and blood flow Doppler imaging. Background 4D echocardiography has the potential to improv...

Objective Vascular Ehlers–Danlos syndrome (vEDS) is associated with arterial ruptures due to a mutant gene encoding collagen type III (Col-III). To better understand the role of Col-III, we aimed at evaluating aortic stiffness and dynamic stiffening in vEDS mouse models, with either a quantitative (col3KO mice) or a qualitative Col-III defect (col3...

The assessment of myocardial fiber disarray is of major interest for the study of the progression of myocardial disease. However, time-resolved imaging of the myocardial structure remains unavailable in clinical practice. In this study, we introduce 3D Backscatter Tensor Imaging (3D-BTI), an entirely novel ultrasound-based imaging technique that ca...

Background Elastic properties of arteries have long been recognized as playing a major role in the cardiovascular system. However, non-invasive in vivo assessment of local arterial stiffness remains challenging and imprecise as current techniques rely on indirect estimates such as wall deformation or pulse wave velocity. Recently, Shear Wave Elasto...

Radiofrequency (RF) ablation of the myocardium is used to treat various cardiac arrhythmias. The size, spacing, and transmurality of lesions have been shown to affect the success of the ablation procedure; however, there is currently no method to directly image the size and formation of ablation lesions in real time. Intracardiac myocardial elastog...

Pulse wave imaging (PWI) is a noninvasive technique for tracking the propagation of the pulse wave along the arterial wall. The 3-D ultrasound imaging would aid in objectively estimating the pulse wave velocity (PWV) vector. This paper aims to introduce a novel PWV estimation method along the propagation direction, validate it in phantoms, and test...

Strain evaluation is of major interest in clinical cardiology as it can quantify the cardiac function. Myocardial elastography, a radio-frequency (RF)-based cross-correlation method, has been developed to evaluate the local strain distribution in the heart in vivo. However, inhomogeneities such as RF ablation lesions or infarction require a three-d...

Very high frame rate ultrasound imaging has enabled the development of novel imaging modalities such as the functional imaging of the brain, cardiac electrophysiology, and the quantitative real-time imaging of the intrinsic mechanical properties of tumors, to name a few. We present here the extension of Ultrafast Ultrasound Imaging in three dimensi...

Coherent compounding has been investigated as a possible means of increasing strain estimation accuracy while retaining high frame rate; however, the optimal parameters that yield the best strain estimate have yet to be determined. Three transmit parameters were investigated: the number of transmits, the subaperture size, and the angular aperture....

In biological tissue, an increase in elasticity is often a marker of abnormalities. Techniques such as quasi-static ultrasound elastography have been developed to assess the strain distribution in soft tissues in two dimensions using a quasi-static compression. However, as abnormalities can exhibit very heterogeneous shapes, a three dimensional app...

Introduction: Radiofrequency (RF) ablation is used for treatment of arrhythmia; however, currently there are no direct visualization or assessment of lesion formation. The size, spacing, and transmurality of lesions affects the success of the procedure; however, there is a lack of real-time feedback during the procedure. Intracardiac Myocardial ela...

Ultrafast Doppler imaging was introduced as a technique to quantify blood flow in an entire 2-D field of view, expanding the field of application of ultrasound imaging to the highly sensitive anatomical and functional mapping of blood vessels. We have recently developed 3-D ultrafast ultrasound imaging, a technique that can produce thousands of ult...

Over the last ten years, shear wave elastography (SWE) has seen considerable development and is now routinely used in clinics to provide mechanical characterization of tissues to improve diagnosis. The most advanced technique relies on the use of an ultrafast scanner to generate and image shear waves in real time in a 2-D plane at several thousands...

The feasibility of Shear Wave Elastography (SWE) in arteries for cardiovascular risk assessment remains to be investigated as the artery’s thin wall and intricate material properties induce complex shear wave (SW) propagation phenomena. To better understand the SW physics in bounded media, we proposed an in-vitro validated finite element model capa...

In this thesis, we investigated various aspects of ultrafast ultrasound imaging of the cardiovascular system. First, we quantified the arterial stiffness with shear wave imaging and its dependence with stress, anisotropy and blood pressure. Thanks to experiments on an ex vivo horse artery and on in vivo rat arteries we measured the dependence with...

Shear wave elastography imaging techniques provide quantitative measurement of soft tissues elastic properties. Tendons, muscles and cerebral tissues are composed of fibers, which induce a strong anisotropic effect on the mechanical behavior. Currently, these tissues cannot be accurately represented by existing elastography phantoms. Recently, a no...

Supersonic shear wave imaging (SSI) is a noninvasive, ultrasound-based technique to quantify the mechanical properties of bulk tissues by measuring the propagation speed of shear waves (SW) induced in the tissue with an ultrasound transducer. The technique has been successfully validated in liver and breast (tumor) diagnostics and is potentially us...

Very high frame rate ultrasound imaging has recently allowed for the extension of the applications of echography to new fields of study such as the functional imaging of the brain, cardiac electrophysiology, and the quantitative imaging of the intrinsic mechanical properties of tumors, to name a few, non-invasively and in real time. In this study,...

Shear wave elastography can provide quantitative evaluation of soft tissues viscoelastic properties based on the measurement of shear wave speed in the medium. Muscular and cerebral tissues are composed of fibers which induce a strong anisotropic effect on the mechanical behavior. Currently, these tissues cannot be accurately represented by existin...

Background, Motivation and Objective Shear Wave Imaging (SWI) is a non-invasive technique for myocardial stiffness quantitative mapping. Recently different techniques have been proposed to improve cardiac shear wave motion mapping. Pulse-Inversion Harmonic SWI [P. Song, et al., IEEE TMI, 2013] by limiting reverberation and clutter noise artifacts,...

Supersonic ShearWave Imaging (SSI) is based on two major concepts: ultrasound radiation force and ultrafast imaging. SSI provides a quantitative mapping of the stiffness of soft tissues in real-time. For cardiac applications, the complex structure of the myocardium (anisotropic and viscoelastic medium) induces the propagation of multiple shear wave...

The assessment of fiber architecture is of major interest in the progression of myocardial disease. Recent techniques such as magnetic resonance diffusion tensor imaging (MR-DTI) or ultrasound elastic tensor imaging (ETI) can derive the fiber directions by measuring the anisotropy of water diffusion or tissue elasticity, but these techniques presen...

Noninvasive ultrafast imaging of intrinsic waves such as electromechanical waves or remotely induced shear waves in elastography imaging techniques for human cardiac applications remains challenging. In this paper, we propose ultrafast imaging of the heart with adapted sector size by coherently compounding diverging waves emitted from a standard tr...

Background: The generation of shear waves from an ultrasound focused beam has been developed as a major concept for remote palpation. For myocardial application, the characteristics of the focal spot and the resulting shear wave profile will depend on both the design of the transducer and the presence of the cardiac fibers.

Background: Mice models of arterial disease are critical for a better understanding of vascular diseases. Pulse wave velocity (PWV) is widely used as an index of arterial stiffness. Indeed, its evaluation has been reported through invasive measurement by the ratio of distance between 2 arterial cannula tips divided by transit time or non-invasively...

Supersonic shear wave imaging (SSI) has recently emerged as a reliable technique for soft tissue characterization in bulk tissues (e.g. in the context of breast and liver cancer diagnostics). Another promising application of SSI is arterial stiffness assessment, though challenged by complex shear wave (SW) propagation phenomena in this thin-walled...

The concept of coherent compound for diverging waves is proposed to make Shear Wave Imaging at very high frame rate (up to 4000 images/sec) with a conventional cardiac phased array probe non invasively in a beating human heart. The first goal of this study was to demonstrate the improvement of the imaging performances based on spatial coherent comp...