A new pulsed wave Doppler ultrasound system to measure bloodvelocities beyond the Nyquist limit

摘要

Conventional pulsed wave (PW) Doppler ultrasound systems measurenblood velocities unambiguously as long as the velocities are less thannthe Nyquist velocity. Here, a new PW Doppler ultrasound system isndescribed, which can measure velocities up to 4.5 times higher than thenNyquist velocity. The new PW system presented here utilizes twonultrasound carrier frequencies, such that an appropriate processing ofnthe Doppler frequencies results in an extended mean-velocity range. Withnthis extended mean-velocity information, the complex Doppler signal isninterpolated to reconstruct aliased Doppler spectra. The interpolationnalgorithm has been tested by computer simulations demonstrating thencapabilities and limits. The integration into a commercial Dopplernscanner allowed the evaluation of the new PW system in real time. Innvitro and in vivo tests demonstrate the effective reconstruction ofnhighly aliased Doppler spectra