XDoppler: Cross-Correlation of Orthogonal Apertures for 3D Blood Flow Imaging

Row column addressing (RCA) transducers have the potential to provide volumetric imaging at ultrafast frame rate using a low channel count over a large field of view. In previous works we have shown that vascular imaging of large arteries as well as functional neuroimaging of the rat brain were feasible using RCA orthogonal plane wave imaging (OPW), but these applications required to transmit many plane waves, significantly reducing the frame rate. In this study, we introduce XDoppler imaging, a novel method to increase the performances of RCA flow imaging by taking advantage of the blood spatial decorrelation statistics combined with the limited spatial overlap of the point spread functions (PSF) of the two orthogonal apertures of the RCA transducer. We provide at first a theoretical basis to understand how the correlation operation reduces the sidelobe level. Then, we demonstrate both in vitro and in vivo in the human carotid artery and in the rat brain that XDoppler provides a significant gain in contrast-to-noise ratio (CNR) (between 3 and 6 dB depending on the application) compared to OPW. This improvement also leads to a sensitivity increase in the rat brain as more blood vessels are detected by XDoppler imaging.