Vector Doppler: spatial sampling analysis and presentation techniques for real time systems

Abstract

The aim of the vector Doppler (VD) technique is the quantitative reconstruction of a velocity field independent of the ultrasonic probe axis to flow angle. In particular, vector Doppler is useful for studying vascular pathologies related to complex blood flow conditions. Clinical applications require a real-time operating mode and the capability to perform Doppler measurements over a defined volume. The combination of these two characteristics produces a real-time vector velocity map. In previous works we investigated the theory of pulsed-wave (PW) vector Doppler and developed an experimental system capable of producing off-line 3-D vector velocity maps. Afterward, for producing dynamic velocity vector maps, we realized a new 2-D vector Doppler system based on a modified commercial echograph. The measurement and presentation of a vector velocity field requires correct spatial sampling that must satisfy the Shannon criterion. In this work we tackle this problem, establishing a relationship between sampling steps and scanning system characteristics. Another problem posed by the vector Doppler technique is the data representation in realtime that should be easy to interpret for the physician. With this in mind we attempt a multimedia solution that uses both interpolated images and sound to represent the information of the measured vector velocity map. These presentation techniques are tested for real-time scanning on flow phantoms and preliminary measurements in vivo on a human carotid artery.