Spatial and temporal resolution of aortic Doppler blood velocity signals in normal human subjects

We have used digital, microcomputer-based methods for the numerical analysis of pulsed, range-gated, ultrasonic Doppler blood velocity signals recorded with an axially aimed transducer from the ascending aorta of normal subjects. We investigated the spatial, temporal and amplitude resolution of our methods for recording and analysis, comparing aortic signals with test signals from a sine wave function generator. The spatial resolution of our system was found to be adequate in spite of the use of a relatively large sample volume. The temporal resolution was significantly influenced by the rate of change of velocity which affected the results of discrete fast Fourier transform analysis. The rate of increase in aortic blood velocity at the start of ejection was linear, following an initial jump in velocity. The amplitude resolution was affected by fluctuations in the amplitude of the Doppler signals. We conclude that our methods do not exaggerate the bluntness of the aortic velocity profile or the linearity of the increase in blood velocity at the start of left ventricular ejection.