Directional Representations of 4D Echocardiography for Temporal Quantification of LV Volume

Real-time acquisition via four-dimensional (3D plus time) ultrasound obviates the need for slice registration and reconstruction, leaving segmentation as the only barrier to an automated, rapid, and clinically applicable calculation of accurate left ventricular cavity volumes and ejection fraction. Speckle noise corrupts ultrasound data by introducing sharp changes in an image intensity profile, while attenuation alters the intensity of equally significant cardiac structures, depending on orientation with respect to the position of the ultrasound beam. These properties suggest that measures based on phase information rather than intensity are appropriate for denoising and boundary (surface) detection. Our method relies on the expansion of temporal volume data on a family of basis functions called Brushlets. These basis functions decompose a signal into distinct patterns of oriented textures. Projected coefficients are associated with distinct “brush strokes” of a particular size (width) and orientation (direction). Brushlet decompositions are invariant to intensity (contrast range) but depend on the spatial frequency content of a signal. Preliminary results of this directional spacefrequency analysis applied to both phantoms and clinical data are presented. The method will be used to clinically evaluate 4D data and to extract and quantify heart LV volumes.