Speckle tracking in intracardiac echocardiography for the assessment of myocardial deformation.

Intracardiac echocardiography (ICE) has proven to be useful for online anatomical imaging during catheterization. Our objective was to develop a speckle tracking method for myocardial motion estimation from ICE image sequences in order to provide a mean for regional functional imaging. Our approach was to solve two problems in motion estimation from 2-D ICE image sequences: nonrigid myocardial deformation and speckle decorrelation. To achieve robust noise resistance, we employed maximum likelihood estimation while fully exploiting ultrasound speckle statistics, and treated the maximization of motion probability as the minimization of an energy function. Nonrigid myocardial deformation was estimated by optimizing this energy function within a framework of parametric elastic registration. Evaluation of the method was carried out using a computer model that synthesized echocardiographic image sequences, and subsequently an animal model that provided continuous ICE images as well as reference measurements using sonomicrometry crystals. In conclusion, accurate estimation of regional myocardial deformation from ICE by novel speckle tracking is feasible. This approach may have important clinical implications for multimodal imaging during catheterization.