Single-pulse tissue doppler using synthetic transmit beams

Tissue Doppler imaging (TDI) is a common technique for investigating myocardial function. Typically, B-mode data and TDI data are recorded using separate acquisitions and combined into a single, color overlaid image. In this work, we present a novel method for TDI imaging, where both TDI and B-mode are created from the same acquisition. Velocities are calculated from the phase shift between neighboring transmit events in the B-mode scan; hence the name singlepulse tissue Doppler (SPTD). Using a novel transmit beam interleaving pattern, this method provides TDI and B-mode at the same high frame rate with an adjustable Nyquist velocity limit. Through simulations and measurements, this work investigates the bias and variance of the SPTD velocities and compares the estimates to those of the conventional TDI autocorrelation estimation method. The results showed that the method introduces an additional bias and variance in the velocity estimates compared with conventional TDI. However, by applying bias compensation, the SPTD velocity estimates were close to those of regular TDI. Using SPTD, the whole left ventricle was imaged within a 65-degree sector at a frame rate of 110 frames per second (43 transmissions per frame).