A novel approach for reducing Multi Line Transmission cross-talks using 2D transducer arrays

Multi-Line Transmission (MLT) is a potential approach to increase the framerate in 3D echocardiography, but suffers from artifacts caused by the cross-talk between the simultaneously transmitted beams. Using transducers with a rectangular geometry, most of the acoustic side lobe energy will be concentrated around the azimuth and elevation center planes. Therefore, we propose to position the parallel-transmitted beams along the diagonal of the transducer. Situations with up to 5 MLT where simulated using Field II (DTU, Denmark) for a typical cardiac 2D phased array (60x48 elements, 2.5 MHz center frequency). Using the proposed MLT disposition, a volume image can be acquired by scanning along the second diagonal of the transducer, with an increase in frame rate equal to the number of MLT. The resulting volume will be a 3D sector rotated around the transducer central axis. Boundary artifacts at the edges of each MLT zone was omitted by applying a custom scan sequence, scanning from the zone edges and inwards. Simulations showed that the MLT cross talks were decreased from levels above -35 dB when using conventional MLT dispositions to levels below -60dB when aligning up to 5 MLT along the diagonal as proposed. The proposed 3D scan pattern takes advantage of the rectangular geometry of a 2D ultrasound transducer to reduce the cross talk between simultaneously transmitted ultrasound beams to an acceptable level. The resulting imaging frame rate can be significantly increased while providing a large field of view and sufficiently narrow ultrasound beams to take advantage of harmonic imaging.