Brain tissue motion estimation: 2D speckle tracking using synthetic lateral phase technique

It is well known that the pulsatile motion of brain parenchyma results from cardiac and breathing cycles. The brain displaces in three directions, mediolateral, anteroposterior and cephalocaudal. We propose in this work to measure 2D displacement vector (mediolateral and anteroposterior componenst) of an imaged area of the brain through the right temporal window. A 2D speckle tracking based on the phase zero-crossing detection of correlation was applied to RadioFrequency signals to estimate the displacement vector. However, unlike the axial direction, the fundamental limitation for lateral tracking motion is the lack of RadioFrequency phase information. The synthetic lateral phase (SLP) technique was then used to create synthetic phase in this direction. Zero-crossing detection was then applied to the 2D complex phase of the synthetic RF signal. The advantage of SLP technique is that there is no need to modify the emission/reception ultrasound process to create synthetic phase in the lateral direction.