A time-shared ultrasound Doppler measurement and 2-D imaging system

Methods for obtaining image-guided Doppler blood velocity measurements are briefly reviewed. Preference is given to a time-sharing scheme in which the Doppler measurement is turned off during the data-acquisition period for a 2-D image frame (typically 20 ms). The signal dropout that occurs during the image-updating period is removed from the Doppler audio by inserting a synthetic signal segment. The synthetic signal is generated by passing white noise through a discrete-time FIR (finite-impulse response) filter with filter coefficients that are a windowed version of the Doppler signal measured immediately prior to the imaging interrupt. It is shown that the artificial signal has spectral properties (and thus audible sound) similar to those of the real Doppler signal segment on which it is based. The time-sharing method is analyzed and evaluated experimentally, using dedicated hardware. The proposed algorithm allows for the design of time-shared Doppler/imaging systems that carry out pulsed or continuous Doppler measurements with essentially real-time imaging guidance.