Evaluation of 2-D speckle tracking based strain rate imaging (SRI) using a 3-D heart simulation model

Preliminary 2D SRI results from a porcine heart model showed significant average residual accumulation error (RAE) in the total displacement, similar to widely reported baseline drift artifacts in SRI. Therefore, to understand the performance of 2D SRI methods in a controlled 3D environment, a left-ventricle simulation model with physiological deformation was developed. Torsion was added to move tissue in and out of the image plane. A phased-array imaging system was simulated to generate 2D image sequences for typical cardiac scans. Results show the presence of RAE, which reaches a minimum at a frame rate (FR) of 75 frame/cycle corresponding to 2-3% peak frame-to-frame strain. RAE increases as torsion increases. In addition. the RAE map also spatially correlates well with both out-of-plane motion and cross-correlation coefficient maps. These results suggest that out-of-plane motion plays a significant role in RAE. To optimize SNR in displacement estimates a retrospective processing strategy employing different frame intervals for different periods in a cardiac cycle is presented.