TOWARDS 3-D TISSUE DOPPLER ULTRAFAST ECHOCARDIOGRAPHY: AN IN VITRO STUDY

International audienceBackground, Motivation and ObjectiveThe emergence of ultrafast imaging allowed new insights into cardiac deformation/motion analysis that enabled new advancements in clinical diagnosis. Several studies showed that a good compromise between the temporal and the spatial resolution can be obtained by transmitting multiple focused beams (MLT) simultaneously. However, the currentimplementation of MLT in 3D cannot be used in dynamic conditions as it was obtained synthetically, by summing the Single Line Transmit (SLT) events before beamforming [Ortega et al., TUFFC, 2016]. The objective of this study is to evaluate for the first time the performance of MLT in 3D ultrasound under dynamic conditions. Statement of Contribution/MethodsThe 3D images were acquired by using four Verasonics research scanners, each of them controlling 8-by-32 elements of a 32-by-32, 3 MHz, Vermon ultrasound transducer. The scan volume was created by stitching 30 triangular sectors (each of angular width = 40°) along the azimuth angular direction. For each triangular sector, 9 transmission events were used for insonifying a full sector by sending simultaneously three focused beams. Thus, the total number of transmissions was 270 corresponding to 27 (elevational) x 30 (azimuthal) focal beams. The Pulse Repetition Frequency (PRF) was set to 2250. Our in vitro model was a tissue mimicking spinning disc having a diameter of 11 cm whose speed could be controlled by a step motor. The disk was placed at approximately 3 cm away from transducer and the image depth was 6.8 cm. Doppler velocities were estimated from the IQ signals using a 2D auto-correlator and a packet length of 7.Results/DiscussionThis study demonstrates the feasibility of Doppler velocity estimation for 3D MLT images. The estimated values presented in the image were in agreement with the expected velocities since the relative mean error was 3.5%. We obtained a three-fold increase in volume rate compared with focus imaging. Analyzing further different MLT/MLA configurations would allow increasing the frequency of volumes and obtaining the optimal compromise between high volume rate and quality color Doppler