High frame rate 3D tissue velocity imaging using sub-aperture beamforming: A pilot study in vivo

Implementation of 3D high frame rate (HFR) tissue Doppler imaging (TDI) typically requires a fully wired matrix probe. However, such probes remain impractical for use in a clinical setting. Therefore, clinical matrix arrays rely on sub-aperture (SAP) beamforming. This makes diverging wave (DW) imaging challenging as side- and grating-lobes arise from the simultaneous reconstruction of image lines with considerably different orientations. We have previously shown in computer simulations that these difficulties could be mitigated by using a sparse transmit sequence. The present study looked at the implementation of this sequence in a clinical system. 3D TDI was acquired in vivo at 610 vol/s and compared against conventional TDI (i.e. focused transmissions). The velocity curves obtained from both methods were similar (cross correlation = 0.90 ± 0.11) and the full left ventricle could be imaged at HFR in a single acquisition using the 3D DW sequence. Overall, this study supports the feasibility of HFR 3D TDI in a clinical system, despite the limitations of SAP beamforming.