1Beam Steering Approach for Speckle Characterization and Out-of-Plane Motion Estimation in Real Tissue

Abstract—Out-of-plane motion in freehand 3D ultrasound can be estimated using the correlation of corresponding patches, leading to sensorless freehand 3D ultrasound systems. Previous work has shown that the motion estimation in a beef tissue is sys-tematically underestimated by approximately 33 % and that it can be improved to approximately 25 % by limiting the correlation calculation to the fully developed speckle (FDS) patches [1]. The improvement in the accuracy is limited because FDS patches are rare in real tissue. Here, we propose beam steering for detecting FDS patches and we show that it significantly improves speckle detection. We further experiment the effect of beam steering on out-of-plane motion estimation using ex-vivo beef liver and steak experiment. Without steered images, we find a 17 % error in the liver experiment. Beam steering reduces the error to 9%, a significant improvement which is mainly due to enhanced FDS detection. Beef steak results are even more promising: 14.8% error without beam steering is reduced to 3.2 % error. I