Key result
Color Doppler accurately measures low and medium velocities in vitro but fails under intense turbulence.
Why the study?
The accuracy of velocity measurements obtained through color Doppler flow mapping using digital image analysis had not been fully validated in vitro across different flow velocities.
Color Doppler flow mapping combined with a digital unwrapping algorithm provides accurate velocity measurements at low and medium velocities, but fails at high velocities due to turbulence.
Color Doppler should not guide high-velocity assessments clinically; leaves open its role for low-velocity flows pending in vivo validation.
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.
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Walker et al. (1994) studied this question. Color Doppler flow mapping (CDFM) with digital image analysis vs. True velocity was evaluated on Accuracy of velocity measurements. Color Doppler flow mapping with digital image analysis accurately measured low and medium velocities in an in vitro flow phantom, but was inaccurate at high velocities due to intense turbulence.
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