Easy-to-use blood velocity measurement instruments

This paper describes a new kind of clinical instrument designed to allow non-specialists to quantitatively measure blood velocity. The instrument's, design utilizes vector continuous-wave (CW) Doppler. Vector CW Doppler insonates a volume with simultaneous multiple-angle beams that define a measurement region; within that region, the velocity vector of the blood can be measured independently of the probe orientation. By eliminating the need for simultaneous imaging, and the specially trained technician required for the complicated instrument needed for such imaging, easy and inexpensive blood velocity measurements becomes possible. A prototype for a CW vector Doppler instrument has been used to measure blood velocity in several clinically important arteries: the radial and ulnar in the arm, the femoral in the leg, and the carotid in the neck. We report here on its first clinical use -- monitoring the flow in dialysis access grafts to prevent graft thrombosis. These early clinical results show accuracy and rapid learning of proper instrument use. The design approach presented shows much promise in creating instruments that will provide simple and low-cost-of-use procedures for measurement of blood velocity.