###### Abstract  
Strain imaging of the carotid artery (CA) has demonstrated to be a technique capable of identifying plaque composition. This study assesses the performance of volumetric strain imaging derived from multi-plane acquisitions with a single transducer, with and without displacement compounding. These methods were compared to a reference method using two orthogonally placed transducers. A polyvinyl alcohol phantom was created resembling a stenotic CA bifurcation. A realistic pulsatile flow was imposed on the phantom, resulting in fluid pressures inducing 10% strains. Two orthogonally aligned linear array transducers were connected to two Verasonics systems and fixed in a translation stage. For 120 equally spaced elevational positions, ultrasound series were acquired for a complete cardiac cycle and synchronized using a trigger. Each series consisted of ultrafast plane-wave acquisitions at 3 alternating angles. Inter-frame displacements were estimated using a 3D cross-correlation-based tracking algorithm. Horizontal displacements were acquired using the single probe lateral displacement estimate, the single probe compounded by axial displacement estimates obtained at angles of \(19.47\) and \(-19.47\) degrees, and the dual probe registered axial displacement estimate. After 3D tracking, least squares strain estimations were performed to compare compressive and tensile principal strains in 3D for all methods. The compounding technique clearly outperformed the zero-degree method for the complete cardiac cycle and resulted in more accurate 3D strain estimates. polyvinyl alcohol phantom; bifurcation; dual probe acquisitions; plane wave ultrasound; 3D strain estimation 2018 8 637 [doi:10.3390/app8040637] [urlcore sealed with a thin cap). The latter type is prone to rupture [6; 7]. Since rupture of these plaques has been shown to be one of the main initiators of acute transient ischemic attack or stroke [8], it implies that strain imaging might enable up-front risk stratification of these potentially lethal events. With that it will also provide opportunities for early intervention and hopefully aid in the prevention of these events. Many arterial strain imaging techniques have already been developed and reported, like intravascular techniques [9], which use an US transducer on the tip of a catheter to image from within the lumen, and non-invasive techniques, which image from outside the body [10; 11; 12; 13; 14; 15]. With these techniques, it has been shown that arterial strain distribution correlates with histological composition of plaques in pigs [16] and in humans [2; 17]. For intravascular imaging and non-invasive imaging in longitudinal planes, the US beam is aligned with the principal direction of deformation of the artery (radial for a concentric homogeneous artery), which implies a direct and accurate estimation of the strains in the principal direction using algorithms that only estimate the (axial) displacement component along the beam. For non-invasive strain estimation in transverse planes, accurate estimation of the full 2D displacement vector requires more advanced methods [18; 19; 20; 21]. Until now, all in vivo applied techniques have been primarily based on cross-sectional images of the artery and provide a strain estimation in 2D only. However, as illustrated before, 2D estimation can be problematic in the case of complex motion patterns as a result of longitudinal artery wall displacement [22; 23]. It has been demonstrated that strains are generally smaller in the longitudinal direction than in the radial direction, although the displacement magnitude in the longitudinal direction of the arterial wall equals the magnitude of the radial displacements [24]. Reduced longitudinal artery wall motion was even correlated with cardiovascular outcome [25], which makes an estimate of the full 3D tissue motion in horizontal, vertical, and longitudinal direction even more relevant. Full 3D tissue motion estimation overcomes the following limitations of 2D.