Doppler frequency shift and time-domain velocity enhancement induced by anultrasonographic contrast agent

The aim of this study was to evaluate in rabbit aorta the effect of three b olus doses of Levovist on velocity values measured with spectral Doppler so nography and with time-domain correlation method (color velocity imaging). At each step, a mean peak systolic velocity was calculated from five measur ements. These measurements were taken before injection, at 20 s after, at e very 30 s till the third minute, and at every minute until return to peak s ystolic velocity at baseline value. Total duration of enhancement was noted after each injection. After each injection, once the systolic velocity val ues return to baseline values, a 3 min delay was observed before the follow ing intravenous contrast agent injection was done. With Doppler spectral an alysis, after the first injection, peak systolic velocity enhancement was 1 5 +/- 8.4% (5 to 28%), with a 6.4 +/- 4.3 min duration. After the second in jection, peak systolic velocity enhancement was 15.8 +/- 8.4% (5 to 28%) wi th an 8.8 +/- 4 min duration. After the third injection, it was 14 +/- 9.8% (5 to 34%) with a 13.6 +/- 7.6 min duration (P = 0.04). Peak systolic velo city measured with color velocity imaging remained unchanged after every in jection. Doppler velocities were increased by a bolus injection of a contra st agent. Amplitude was not cumulative with the number of injections but wa s cumulative on its duration. Velocity measurement with time-domain correla tion was not influenced by repeated injections.