Vector Doppler ultrasound for the detection of internal bleeding Free

A vector Doppler (VD) ultrasound system has four advantages over color‐flow Doppler (CFD) in identifying internal bleeding: (1) measures instantaneous velocity more accurately, (2) measures flows perpendicular to the transmitter, (3) distinguishes between flows at different depths, and (4) detects the 3‐D direction of the flow. A real‐time vector Doppler system has been built and tested in vitro. The system consists of one focused transmitting/receiving transducer (10 mm diameter, 50 mm curvature, 5 MHz frequency) and four receiver transducers (5 mm diameter, flat discs, 5 MHz frequency). The signals are passed through analog filters and preamplifiers and then digitized at 20 MHz to obtain a Doppler signal. A digital signal processing algorithm is implemented to calculate flow direction from a combination of the five received signals as well as remove error from systematic phase shifts inherent in the instrumentation. The software was also designed to decrease the time it takes a user to locate arterial flow vessels. The system was tested using two flow phantoms: a moving string to verify accuracy and precision of the velocity, and cornstarch flowing through a tube to simulate blood flow. For both phantoms, device accuracy was tested over a range of angles and velocities.