Assessment of the accuracy of color Doppler flow mapping by digital image analysis

An in vitro steady flow experiment was performed in order to test the accuracy of velocity measurements obtained through color Doppler flow mapping (CDFM). Using the American Society of Echocardiography (ASE) flow phantom, low (maximum velocity = 60 cm/sec), medium (maximum velocity = 300 cm/sec) and high (maximum velocity = 600 cm/sec) speed accelerating flow fields, in which multiple aliases were visible, were imaged. A fully automatic computer algorithm was used to unwrap the aliases and to convert the CDFM to digital velocity. Packet size and wall filter frequency on the ultrasound machine were varied and the measured velocity compared to the true velocity. The results show that the velocity obtained in this way from the CDFM is very accurate at the low and medium velocities, but for the high velocity the turbulence is too intense to obtain an accurate result. There was no marked difference between the data for different packet sizes or wall filter settings.