Real time multicomponent echo particle image velocimetry technique for opaque flow imaging
TL;DR: In this article, a contrast-based ultrasonic particle imaging technique (echo PIV) was used to measure multi-component velocity vectors in opaque flows with excellent temporal and spatial resolution.
Abstract: This letter reports on a contrast-based ultrasonic particle imaging technique (echo PIV) for measuring multicomponent velocity vectors in opaque flows with excellent temporal (up to 0.5ms) and spatial (up to 0.4mm) resolution. Ultrasound contrast microbubbles are used as flow tracers, and digitally acquired rf data are converted into B-mode images for PIV analysis. Here, velocity fields from various flow patterns (including rotating and transient vortex flows) that are difficult to measure using other opaque flow methods such as ultrasound Doppler or magnetic resonance imaging are measured using echo PIV. This nonintrusive technique should be a promising addition to opaque flow diagnostics.
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TL;DR: The E-PIV technique appears to be capable of evaluating the major flow features in the ventricles, however, the bounded spatial resolution of ultrasound imaging limits the small-scale features of ventricular flow to be revealed.
Abstract: Background In this study, the functionality of echocardiographic particle imaging velocimetry (E-PIV) was compared with that of digital particle imaging velocimetry (D-PIV) in an in vitro model. In addition, its capability was assessed in the clinical in vivo setting to obtain the ventricular flow pattern in normal subjects, in patients with dilated cardiomyopathy, and in patients with mechanical and bioprosthetic mitral valves. Methods A silicon sac simulating the human left ventricle in combination with prosthetic heart valves, controlled by a pulsed-flow duplicator, was used as the in vitro model. Particle-seeded flow images were acquired (1) using a high-speed camera from the mid plane of the sac, illuminated by a laser sheet for D-PIV, and (2) using a Siemens Sequoia system at a frame rate of 60 Hz for E-PIV. Data analysis was performed with PIVview software for D-PIV and Omega Flow software for E-PIV. E-PIV processing was then applied to contrast echocardiographic image sets obtained during left ventricular cavity opacification with a lipid-shelled microbubble agent to assess spatial patterns of intracavitary flow in the clinical setting. Results The velocity vectors obtained using both the E-PIV and the D-PIV methods compared well for the direction of flow. The streamlines were also found to be similar in the data obtained using both methods. However, because of the superior spatial resolution of D-PIV, some smaller scale details were not revealed by E-PIV. The application of E-PIV to the human heart resulted in reproducible flow patterns in echocardiographic images taken within different time frames or by independent examiners. Conclusions The E-PIV technique appears to be capable of evaluating the major flow features in the ventricles. However, the bounded spatial resolution of ultrasound imaging limits the small-scale features of ventricular flow to be revealed.
191 citations
Additional excerpts
...Several attempts have been made to incorporate quantitative fluid dynamics into echocardiography using particle-tracking algorithms.(9,10) This echocardiographic approach has received further attention in the clinical setting,(11,12) mainly due to its higher image quality and potential for the assessment of intraventricular blood flow....
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TL;DR: A number of whole-field blood velocity measurement techniques are concisely reviewed, focusing on optical measurement techniques for in vivo applications, such as laser Doppler velocimetry, laser speckle contrast imaging and particle image velocIMetry (including particle tracking).
Abstract: In this article a number of whole-field blood velocity measurement techniques are concisely reviewed. We primarily focus on optical measurement techniques for in vivo applications, such as laser Doppler velocimetry (including time varying speckle), laser speckle contrast imaging and particle image velocimetry (including particle tracking). We also briefly describe nuclear magnetic resonance and ultrasound particle image velocimetry, two techniques that do not rely on optical access, but that are of importance to in vivo whole-field blood velocity measurement. Typical applications for whole-field methods are perfusion monitoring, the investigation of instantaneous blood flow patterns, the derivation of endothelial shear stress distributions from velocity fields, and the measurement of blood volume flow rates. These applications require individual treatment in terms of spatial and temporal resolution and number of measured velocity components. The requirements further differ for the investigation of macro-, meso-, and microscale blood flows. In this review we describe and classify those requirements and present techniques that satisfy them.
154 citations
Cites background from "Real time multicomponent echo parti..."
...Zheng et al. (2006) report a spatial resolution of up to 0.4 mm and a temporal resolution of up to 0.5 ms. 3.5 Nuclear magnetic resonance imaging Nucleons have an angular momentum which leads to a quantized magnetic momentum or spin....
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...Kim et al. (2004a, b); Zheng et al. (2005) and Zheng et al. (2006) determined flow profiles in artificial models of arteries and in a rotating flow apparatus....
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TL;DR: A comprehensive review on current imaging techniques, state‐of‐the‐art advancements and applications, and general perspectives on the prospects for these modalities in the clinical realm is presented.
Abstract: Physics has delivered extraordinary developments in almost every facet of modern life. From the humble thermometer and stethoscope to X-Ray, CT, MRI, ultrasound, PET and radiotherapy, our health has been transformed by these advances yielding both morphological and functional metrics. Recently high resolution label-free imaging of the microcirculation at clinically relevant depths has become available in the research domain. In this paper, we present a comprehensive review on current imaging techniques, state-of-the-art advancements and applications, and general perspectives on the prospects for these modalities in the clinical realm.
120 citations
TL;DR: An overview of the history, typical components and challenges of ultrasound image velocimetry can be found in this paper, where the basic principles of ultrasound imaging image formation are summarized, as well as various techniques to estimate flow velocities; the emphasis is on correlation-based techniques.
Abstract: Whole-field velocity measurement techniques based on ultrasound imaging (a.k.a. ‘ultrasound imaging velocimetry’ or ‘echo-PIV’) have received significant attention from the fluid mechanics community in the last decade, in particular because of their ability to obtain velocity fields in flows that elude characterisation by conventional optical methods. In this review, an overview is given of the history, typical components and challenges of these techniques. The basic principles of ultrasound image formation are summarised, as well as various techniques to estimate flow velocities; the emphasis is on correlation-based techniques. Examples are given for a wide range of applications, including in vivo cardiovascular flow measurements, the characterisation of sediment transport and the characterisation of complex non-Newtonian fluids. To conclude, future opportunities are identified. These encompass not just optimisation of the accuracy and dynamic range, but also extension to other application areas.
97 citations
Cites background from "Real time multicomponent echo parti..."
...Examples include Optison (GE Healthcare, Kim et al. 2004a; Zheng et al. 2006; Westerdale et al. 2011), Definity (Lantheus Medical Imaging, North Billerica, MA; Kheradvar et al....
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...Examples include Optison (GE Healthcare, Kim et al. 2004a; Zheng et al. 2006; Westerdale et al. 2011), Definity (Lantheus Medical Imaging, North Billerica, MA; Kheradvar et al. 2010; Walker et al. 2014), Levovist (Schering/Bayer; Manneville et al. 2001) and SonoVue (Bracco; Zhang et al. 2011;…...
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...Examples include Optison (GE Healthcare, Kim et al. 2004a; Zheng et al. 2006; Westerdale et al. 2011), Definity (Lantheus Medical Imaging, North Billerica, MA; Kheradvar et al. 2010; Walker et al. 2014), Levovist (Schering/Bayer; Manneville et al. 2001) and SonoVue (Bracco; Zhang et al. 2011; Poelma and Fraser 2013; Poelma et al. 2011)....
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...This was done for increasingly complex flows: initially using steady laminar flow (Beulen et al. 2010; Zheng et al. 2006; Qian et al. 2010; Niu et al. 2010; Poelma et al. 2012), followed by pulsatile flows (Kim et al. 2004b; Poelma et al. 2011) and ultimately in flow phantoms....
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...This was done for increasingly complex flows: initially using steady laminar flow (Beulen et al. 2010; Zheng et al. 2006; Qian et al. 2010; Niu et al. 2010; Poelma et al. 2012), followed by pulsatile flows (Kim et al....
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TL;DR: Echo PIV provides accurate velocity vector and WSR measurements in the carotid bifurcation and has significant potential as a clinical tool for cardiovascular hemodynamics evaluation.
Abstract: Noninvasive, easy-to-use and accurate measurements of wall shear stress (WSS) in human blood vessels have always been challenging in clinical applications. Echo particle image velocimetry (Echo PIV) has shown promise for clinical measurements of local hemodynamics and wall shear rate. Thus far, however, the method has only been validated under simple flow conditions. In this study, we validated Echo PIV under in vitro and in vivo conditions. For in vitro validation, we used an anatomically correct, compliant carotid bifurcation flow phantom with pulsatile flow conditions, using optical particle image velocimetry (optical PIV) as the reference standard. For in vivo validation, we compared Echo PIV-derived 2-D velocity fields obtained at the carotid bifurcation in five normal subjects against phase-contrast magnetic resonance imaging (PC-MRI)-derived velocity measurements obtained at the same locations. For both studies, time-dependent, 2-D, two-component velocity vectors; peak/centerline velocity, flow rate and wall shear rate (WSR) waveforms at the common carotid artery (CCA), carotid bifurcation and distal internal carotid artery (ICA) were examined. Linear regression, correlation analysis and Bland-Altman analysis were used to quantify the agreement of different waveforms measured by the two techniques. In vitro results showed that Echo PIV produced good images of time-dependent velocity vector maps over the cardiac cycle with excellent temporal (up to 0.7 ms) and spatial (∼0.5 mm) resolutions and quality, comparable with optical PIV results. Further, good agreement was found between Echo PIV and optical PIV results for velocity and WSR measurements. In vivo results also showed good agreement between Echo PIV velocities and phase contrast MRI velocities. We conclude that Echo PIV provides accurate velocity vector and WSR measurements in the carotid bifurcation and has significant potential as a clinical tool for cardiovascular hemodynamics evaluation.
84 citations
References
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TL;DR: The ability to non-invasively image molecular events with targeted microbubbles is likely to be important for characterizing pathophysiology and for developing new therapeutic strategies in the treatment of cardiovascular and neoplastic diseases.
Abstract: Not all bubbles in the bloodstream are detrimental. During the past decade, contrast-enhanced ultrasound has evolved from a purely investigational tool to a routine diagnostic technique. This transformation has been facilitated by advances in the microbubble contrast agents and contrast-specific ultrasound imaging techniques. The ability to non-invasively image molecular events with targeted microbubbles is likely to be important for characterizing pathophysiology and for developing new therapeutic strategies in the treatment of cardiovascular and neoplastic diseases.
797 citations
TL;DR: In this paper, the combination of ultrasound echo images with digital particle image velocimetry (DPIV) methods has resulted in a two-dimensional, two-component velocity field measurement technique appropriate for opaque flow conditions including blood flow in clinical applications.
Abstract: The combination of ultrasound echo images with digital particle image velocimetry (DPIV) methods has resulted in a two-dimensional, two-component velocity field measurement technique appropriate for opaque flow conditions including blood flow in clinical applications. Advanced PIV processing algorithms including an iterative scheme and window offsetting were used to increase the spatial resolution of the velocity measurement to a maximum of 1.8 mm×3.1 mm. Velocity validation tests in fully developed laminar pipe flow showed good agreement with both optical PIV measurements and the expected parabolic profile. A dynamic range of 1 to 60 cm/s has been obtained to date.
181 citations
TL;DR: In this paper, a modified Rayleigh-Plesset model was used to predict a peak negative wall velocity of −680 m/s and peak acceleration of 2×1012m/s2.
Abstract: Fragmentation of an ultrasound contrast agent on the time scale of microseconds provides opportunities for the advancement of microvascular detection, blood flow velocity estimation, and targeted drug delivery. Images captured by high-speed imaging systems show destruction of a microbubble during compression. Peak wall velocity of −700 m/s and peak acceleration of 1.2×1012 m/s2 is observed for insonation with a peak pressure of −1.1 MPa and a center frequency of 2.4 MHz. Theoretical calculations of wall velocity and acceleration using a modified Rayleigh–Plesset model predict a peak negative wall velocity of −680 m/s and peak acceleration of 2×1012 m/s2.
157 citations
TL;DR: Echo PIV is a promising technique for noninvasive measurement of velocity profiles and shear stress in arteries and it is indicated that error in shear from echo PIV was an order of magnitude less than error from current shear measurement methods.
Abstract: Although accurate measurement of velocity profiles, multiple velocity vectors, and shear stress in arteries is important, there is still no easy method to obtain such information in vivo. We report on the utility of combining ultrasound contrast imaging with particle image velocimetry (PIV) for noninvasive measurement of velocity vectors. This method (echo PIV) takes advantage of the strong backscatter characteristics of small gas-filled microbubbles (contrast) seeded into the flow. The method was tested in vitro. The steady flow analytical solution and optical PIV measurements (for pulsatile flow) were used for comparison. When compared to the analytical solution, both echo PIV and optical PIV resolved the steady velocity profile well. Error in shear rate as measured by echo PIV (8%) was comparable to the error of optical PIV (6.5%). In pulsatile flow, echo PIV velocity profiles agreed well with optical PIV profiles. Echo PIV followed the general profile of pulsatile shear stress across the artery but underestimated wall shear at certain time points. However, error in shear from echo PIV was an order of magnitude less than error from current shear measurement methods. These studies indicate that echo PIV is a promising technique for noninvasive measurement of velocity profiles and shear stress.
73 citations
TL;DR: Experimental evidence that the scattering of sound waves by a fluid flow may be used, as a nonintrusive and nonlocal method, to characterize the space-time structure of the flow is reported.
Abstract: We report experimental evidence that the scattering of sound waves by a fluid flow may be used, as a nonintrusive and nonlocal method, to characterize the space-time structure of the flow. The experiment has been performed using, as a test flow, the von Karman vortex street behind a cylinder at a low Reynolds number (Re=50). The results are in good qualitative agreement with earlier experiments on the von Karman vortex street and with recent theoretical developments on sound-velocity interaction
63 citations