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Velocity vector imaging (VVI)
The new off-line software (syngo Velocity Vector Imaging technology [VVI], Siemens) provides angle-independent 2D velocity, strain, and SR. “Feature tracking” of the myocardium with VVI is achieved through the combination of speckle tracking, mitral annulus motion, tissue-blood border detection, and the periodicity of the cardiac cycle using R-R intervals. In order to improve the tracking results, the algorithm applies a carefully designed sequence of intermediate passages to accurately follow myocardial motion. All these passages are performed with the aid of Fourier techniques that ensure a higher accuracy using the periodicity of the heart motion. From the multiple 1-dimensional interrogations, a 2D solution is achieved and the displacement information of the tracked points is obtained. The endocardial border is visually identified by the user and manually outlined. The manual placement of an endocardial tracing over 1 frame is then automatically tracked throughout the cardiac cycle. The software allows editing of the initial trace if the resulting tracking is assessed as suboptimal. The endocardial velocity is derived as the ratio between frame-to-frame displacement and the time interval. The velocity vectors in the 2D plane are displayed throughout the cardiac cycle, representing both the magnitude of the velocity and the direction of the motion (Fig. 1). Strain and SR are obtained by comparing displacement of the speckles in relation to each other along the endocardial contour throughout the cardiac cycle.
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https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3348770/
http://www.onlinejase.com/article/S0894-7317(12)00051-X/pdf
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Ainda estamos longe de definir uma tecnologia única para a fisiologia cardíaca.
Mais ainda de entender completamente o funcionamento cardíaco.
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