A Multigate Pulsed Doppler System with Serial Data Processing

Abstruct-Multigate pulsed Doppler systemsenable the transcutaneous and simultaneous assessment of the velocities in a number of adjacent sample volumes as a continuous function of time. Since the velocity distribution along the ultrasonic beam is readily available, detailed information can be obtained about the time-dependent flow behavior in the major superficial arteries. A multigate pulsed Doppler system processing the information originating from 32 sample volumes in a sequential way ispresented. Serial data processingis achieved by digitizing the range and time-dependent phase signal and performing the required signal processing (filtering and zero crossing counting) in a digital form. The multigate system is connected to a storage unit, enabling online visualization of the recorded velocity profiles over a number of cardiac cycles. Two output modes are available: the velocity distribution as a continuous function of depth at discrete time intervals and the velocities in a number of adjacent sample volumes as a continuous function of time. The number of interactive controls is restricted to only two: the selector of the sample volume for audio output and the HALT command for the digital storage unit. Both controls can be operated by a footswitch, allowing maximal mobility for the investigator. Resenfly the increasing noise level with increasing depth limits the useful exploration range to 45 mm.