The performance of mechanically scanned color flow mapping

The performance of mechanically scanned Color Flow Mapping is analysed. It is shown that the Doppler spectrum is convolved with a scaled version of the Fourier transform of the two-way point spread function of the transducer. This spectral broadening is no larger than the inherent limit of the method if the point spread function shows smooth amplitude variation and little phase variation. The spectral broadening can cause clutter from stationary objects to fall outside the MTI filter stopband and, thereby, alter the estimates of the mean velocity and turbulence. Mechanically scanned and electronically stepped Color Flow Mapping are compared.