Clinical color Doppler ultrasound technology is a popular, noninvasive, real-time, relatively inexpensive imaging modality, which currently allows the 2D visualization of blood flow within the heart and the vascular system. Doppler ultrasound flow velocity measurement is important for the determination of blood/oxygen supply to various organs, arterial wall shear stress, and blood-tissue gas exchange, as well as for the evaluation of myocardial and valvular function. Initially, we have chosen to concentrate on the structure and flow in the carotid artery, due to the simplifications which this geometry allows. During this first year of this investigation we have assembled the necessary instrumentation within a clinical echocardiography laboratory to acquire color Doppler ultrasound images along with time-encoded position and orientation data for the handheld transducer. A carotid artery/neck phantom was designed and fabricated to allow for calibration and testing of both the position/orientation measurement subsystem and the Doppler flow velocity measurement subsystem in a controlled environment. We have transferred the flow velocity images via the HP SONOS 1500 ultrasound system into separate digital values of structure and flow velocity onto the Macintosh Quadra 950 microcomputer system that is the heart of our image reconstruction system. All algorithms and procedures for correcting the flow velocity readings have been designed and outlined in detail. All software has been described in flowcharts, and many of the routines have been written and debugged. Future plans include completion of all software and verification of the methodology and the software, using the phantom with known parameters. Our approach may eventually be adapted by manufacturers of Doppler ultrasound imaging systems for inclusion into such systems.
