IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control
Several clinical settings could benefit from 3D high frame rate (HFR) imaging and in particular, HFR 3D Tissue Doppler Imaging (TDI). To date, the proposed methodologies are based mostly on experimental ultrasound platforms, making their translation to clinical systems non-trivial as these have additional hardware constraints. In particular, clinically used 2D matrix array transducers rely on sub-aperture (SAP) beamforming to limit cabling between the ultrasound probe and the back-end console. Therefore, the present study aimed at assessing the feasibility of HFR 3D TDI using diverging waves (DW) on a clinical transducer with SAP beamforming limitations. Simulation studies showed that the combination of a single DW transmission with SAP beamforming results in severe imaging artifacts due to grating-lobes and reduced penetration. Interestingly, a promising trade-off between image quality and frame rate was achieved for scan sequences with a moderate number of transmit beams. In particular, a sparse sequence with 9 transmissions showed good imaging performance for an imaging sector of 70°x70° at volume rates of ca. 600 Hz. Subsequently, this sequence was implemented in a clinical system and TDI was recorded in-vivo on healthy subjects. Velocity curves were extracted and compared against conventional TDI (i.e. with focused transmit beams). Results showed similar velocities between both beamforming approaches, with a cross-correlation of 0.90±0.11 between the traces of each mode. Overall, this study indicates that HFR 3D TDI is feasible in systems with clinical 2D matrix arrays, despite the limitations of SAP beamforming.