This paper presents a method for measuring pressure changes in deep-tissue vessels using vector velocity ultrasounddata. The large penetration depth is ensured by acquiring data using a low frequency phased arraytransducer. Vascular pressure changes are then calculated from 2-D angle-independent vector velocity fields usinga model based on the Navier-Stokes equations. Experimental scans are performed on a fabricated flow phantomhaving a constriction of 36% at a depth of 100 mm. Scans are carried out using a phased array transducerconnected to the experimental scanner, SARUS. 2-D fields of angle-independent vector velocities are acquiredusing directional synthetic aperture vector flow imaging. The obtained results are evaluated by comparison to a3-D numerical simulation model with equivalent geometry as the designed phantom. The study showed pressuredrops across the constricted phantom varying from -40 Pa to 15 Pa with a standard deviation of 32%, and abias of 25% found relative to the peak simulated pressure drop. This preliminary study shows that pressure canbe estimated non-invasively to a depth that enables cardiac scans, and thereby, the possibility of detecting thepressure drops across the mitral valve.
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