3D cardiac strain imaging using plane wave excitation and feature tracking
01 Oct 2011-pp 740-743
TL;DR: In this article, the authors investigated whether accurate evaluation of cardiac deformation can be achieved with real-time 3D ultrasound imaging using plane-wave excitation and feature tracking, which selectively extract easily identifiable parts of a speckle pattern, and applied feature tracking to clinical 3D echocardiographic data of a three-month old baby.
Abstract: Evaluation of myocardial motion is important in diagnosis of heart diseases. Myocardial strain imaging is desired when assessing myocardial functions, but its clinical applications are mainly limited to two dimensions. As the heart is a fastest-moving organ, it is necessary to develop real-time 3D cardiac strain imaging methods so that complex deformation information can be acquired. Plane wave excitation can provide very high image frame rates. On the other hand, feature tracking, which selectively extract easily identifiable parts of a speckle pattern, can speed up computation time compared to conventional speckle tracking. Thus, the purpose of this study is to investigate whether accurate evaluation of cardiac deformation can be achieved with real-time 3D ultrasound imaging using plane-wave excitation and feature tracking. In this study, we simulated three-dimensional plane-wave excitation (PWE) images with object motion on which speckle tracking and feature tracking methods are applied and compared. Although the image quality of PWE images is lower, we demonstrated that PWE imaging has similar tracking errors in axial displacements when compared with two-way focused images. The computation time for feature tracking is about 500 to 800 times faster than speckle tracking. In terms of the tracking accuracy, the average tracking error for speckle tracking is less than 1%, and the tracking error range for feature tracking is 2 to 10%. If the threshold or the kernel size were larger, the tracking accuracy will be higher. Finally, we apply feature tracking to clinical 3D echocardiographic data of a three-month-old baby. The feature patterns of endo- and epi-cardium were captured partially successful, however, they are not representative of the overall movement of the heart due to limited image quality. It is important to find other ways to identify features and reducing the rate of signal decorrelation on lower quality images in order to improve performance of strain calculations in clinical applications.
Citations
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TL;DR: It is concluded that the GPU implementation of this 3-D subsample estimation algorithm can provide high-quality strain data (i.e., high correlation between the predeformation and the motion-compensated postdeformation radio frequency echo data and high contrast-to-noise ratio strain images) as compared with the conventional3-D quadratic subsample algorithm.
Abstract: Our primary objective of this paper was to extend a previously published 2-D coupled subsample tracking algorithm for 3-D speckle tracking in the framework of ultrasound breast strain elastography. In order to overcome heavy computational cost, we investigated the use of a graphic processing unit (GPU) to accelerate the 3-D coupled subsample speckle tracking method. The performance of the proposed GPU implementation was tested using a tissue-mimicking phantom and in vivo breast ultrasound data. The performance of this 3-D subsample tracking algorithm was compared with the conventional 3-D quadratic subsample estimation algorithm. On the basis of these evaluations, we concluded that the GPU implementation of this 3-D subsample estimation algorithm can provide high-quality strain data (i.e., high correlation between the predeformation and the motion-compensated postdeformation radio frequency echo data and high contrast-to-noise ratio strain images), as compared with the conventional 3-D quadratic subsample algorithm. Using the GPU implementation of the 3-D speckle tracking algorithm, volumetric strain data can be achieved relatively fast (approximately 20 s per volume [2.5 cm $\times2.5$ cm $\times2.5$ cm]).
20 citations
Cites background from "3D cardiac strain imaging using pla..."
...Developments of plane wave ultrasound data acquisition [15], [16] may further accelerate this process....
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TL;DR: An approach that computationally dissects the sample domain into many homogeneous subdomains, wherein subdomain boundaries are formed by applying a betweenness based graphical analysis to the deformation gradient field to identify locations with large discontinuities.
Abstract: Variations in properties, active behavior, injury, scarring, and/or disease can all cause a tissue's mechanical behavior to be heterogeneous. Advances in imaging technology allow for accurate full-field displacement tracking of both in vitro and in vivo deformation from an applied load. While detailed strain fields provide some insight into tissue behavior, material properties are usually determined by fitting stress-strain behavior with a constitutive equation. However, the determination of the mechanical behavior of heterogeneous soft tissue requires a spatially varying constitutive equation (i.e., one in which the material parameters vary with position). We present an approach that computationally dissects the sample domain into many homogeneous subdomains, wherein subdomain boundaries are formed by applying a betweenness based graphical analysis to the deformation gradient field to identify locations with large discontinuities. This novel partitioning technique successfully determined the shape, size and location of regions with locally similar material properties for: (1) a series of simulated soft tissue samples prescribed with both abrupt and gradual changes in anisotropy strength, prescribed fiber alignment, stiffness, and nonlinearity, (2) tissue analogs (PDMS and collagen gels) which were tested biaxially and speckle tracked (3) and soft tissues which exhibited a natural variation in properties (cadaveric supraspinatus tendon), a pathologic variation in properties (thoracic aorta containing transmural plaque), and active behavior (contracting cardiac sheet). The routine enables the dissection of samples computationally rather than physically, allowing for the study of small tissues specimens with unknown and irregular inhomogeneity.
5 citations
References
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TL;DR: It is concluded that the patient's skin should be abraded to reduce impedance, and measurements should be avoided in the first 10 min after electrode placement, to allow satisfactory images.
Abstract: A computer simulation is used to investigate the relationship between skin impedance and image artefacts in electrical impedance tomography. Sets of electrode impedance are generated with a pseudo-random distribution and used to introduce errors in boundary voltage measurements. To simplify the analysis, the non-idealities in the current injection circuit are replaced by a fixed common-mode error term. The boundary voltages are reconstructed into images and inspected. Where the simulated skin impedance remains constant between measurements, large impedances (> 2k omega) do not cause significant degradation of the image. Where the skin impedances 'drift' between measurements, a drift of 5% from a starting impedance of 100 omega is sufficient to cause significant image distortion. If the skin impedances vary randomly between measurements, they have to be less than 10 omega to allow satisfactory images. Skin impedances are typically 100-200 omega at 50 kHz on unprepared skin. These values are sufficient to cause image distortion if they drift over time. It is concluded that the patient's skin should be abraded to reduce impedance, and measurements should be avoided in the first 10 min after electrode placement.
1,976 citations
TL;DR: In this paper, a new ultrasonic method of quantifying regional deformation has been introduced based on the principles of "strain" and'strain rate' imaging, which introduces concepts derived from mechanical engineering which most echocardiographers are not familiar with.
Abstract: The non-invasive quantification of regional myocardial function is an important goal in clinical cardiology. Myocardial thickening/thinning indices is one method of attempting to define regional myocardial function. A new ultrasonic method of quantifying regional deformation has been introduced based on the principles of 'strain' and 'strain rate' imaging. These new imaging modes introduce concepts derived from mechanical engineering which most echocardiographers are not familiar with. In order to maximally exploit these new techniques, an understanding of what they measure is indispensable. This paper will define each of these modalities in terms of physical principles and will give an introduction to the principles of data acquisition and processing required to implement ultrasonic strain and strain rate imaging. In addition, the current status of development of the technique and its limitations will be discussed, together with examples of potential clinical applications.
971 citations
TL;DR: The clinical availability of strain and SR measurement may offer a solution to the ongoing need for quantification of regional and global cardiac function, although these techniques are susceptible to artifact, and further technical development is necessary.
587 citations
"3D cardiac strain imaging using pla..." refers background or methods in this paper
...There are axial strain, the longitudinal strain and the circumferential strain for each point interrogated in any myocardial wall[6], [7],[8]....
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...Doppler is limited by, most importantly, the inability to detect nonaxial motion (angle dependence) and through-plane motion[7]....
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...Due to the limitations of Doppler which is the inability to detect nonaxial motion (angle dependence) [7], speckle tracking was used in our study to get more a meaningful information....
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TL;DR: The new techniques of ultrasonic strain rate and strain imaging of the heart are reviewed in terms of definitions, data acquisition, strain-rate estimation, postprocessing, and parameter extraction.
Abstract: Ultrasonic imaging is the noninvasive clinical imaging modality of choice for diagnosing heart disease. At present, two-dimensional ultrasonic grayscale images provide a relatively cheap, fast, bedside method to study the morphology of the heart. Several methods have been proposed to assess myocardial function. These have been based on either grayscale or motion (velocity) information measured in real-time. However, the quantitative assessment of regional myocardial function remains an important goal in clinical cardiology. To do this, ultrasonic strain and strain-rate imaging have been introduced. In the clinical setting, these techniques currently only allow one component of the true three-dimensional deformation to be measured. Clinical, multidimensional strain (rate) information can currently thus only be obtained by combining data acquired using different transducer positions. Nevertheless, given the appropriate postprocessing, the clinical value of these techniques has already been shown. Moreover, multidimensional strain and strain-rate estimation of the heart in vivo by means of a single ultrasound acquisition has been shown to be feasible. In this paper, the new techniques of ultrasonic strain rate and strain imaging of the heart are reviewed in terms of definitions, data acquisition, strain-rate estimation, postprocessing, and parameter extraction. Their clinical validation and relevance are discussed using clinical examples on relevant cardiac pathology. Based on these examples, suggestions are made for future developments of these techniques.
152 citations
TL;DR: In this article, an angle-independent method was proposed for 3D blood flow velocity measurement that tracks features of the ultrasonic speckle produced by a pulse echo system, where a feature is identified and followed over time to detect motion.
Abstract: This article describes a new angle-independent method suitable for three-dimensional (3-D) blood flow velocity measurement that tracks features of the ultrasonic speckle produced by a pulse echo system. In this method, a feature is identified and followed over time to detect motion. Other blood flow velocity measurement methods typically estimate velocity using one- (1-D) or two-dimensional (2-D) spatial and time information. Speckle decorrelation due to motion in the elevation dimension may hinder this estimate of the true 3-D blood flow velocity vector. Feature tracking is a 3-D method with the ability to measure the true blood velocity vector rather than a projection onto a line or plane. Off-line experiments using a tissue phantom and a real-time volumetric ultrasound imaging system have shown that the local maximum detected value of the speckle signal may be identified and tracked for measuring velocities typical of human blood flow. The limitations of feature tracking, including the uncertainty of the peak location and the duration of the local maxima are discussed. An analysis of the expected error using this method is given.
32 citations