Abstract 19086: Validation Against Laser Particular Velocity Imaging of a New Algorithm of Echo Contrast Tracking Based on Optical Flow Algorithm for Echo Piv Method.
Background: Like optical Particular Velocity Imaging (PIV) analysis, Echo-PIV (EPIV) is usually based on a crosscorrelation technique. Although preliminary studies have shown high spatial resolution, a small dynamic range limits this technique. We have recently described a new method based on Optical flow algorithm applied to corrected raw B mode backscattered images (digital format prior to scan conversion). We thought validate the accuracy of this method againts PIV to describe intraventricular complex flow fields in experimental conditions.
Methods: In vitro model: Atrio-ventricular simulator with a bioprostheses in mitral position. Stroke volume range from 30 to 70 ml, Frame rate (FR) from 178 to 530 i/s. Echo contrast concentration was kept stable along the experimentation Mechanical index :0.21. Image processing. Pre-treatment (1) Removing noise through soft wavelet thresholding method. (2) Decomposition of echo-piv sequence into: (a) geometrical component, (b) textural component (b) and © noise. (3) Based on textural component, the optical flow was estimated through partial derivative equation (Lucas Kanade) Instantaneous and mean (4 cycles) flow velocity fields were obtained. Crosscorrelationalgorithm was appied to PIV images Results. EPIV perfectly describe the intraventricular vortex dynamics as shown in the figure centred on the main intraventricular vortex. Velocity range from 4 to 30 cm/s and from 10 to 120 cm /s in the vortex area and the mitral inflow respectively. Comparing the two methods for Max velocities, highly significant correlation were found (range of coefficient of correlation from 0.50 to 0.65). A slight underestimation was observed with EPIV (range: 2 to 7%).
Conclusions: Our new algorithm grants a coherent ECHOPIV movement estimation with good local and global property. This validation against the reference method allows to plan with confidence, future clinical studies
- © 2010 by American Heart Association, Inc.