Angular error in ultrasound Doppler tissue velocities and its influence on the derived variable peak systolic strain

When recording velocities using ultrasound Doppler, the obtained velocities are always a projection of the true velocities onto the direction from the recording point towards the transducer. In this study we have marked up lines in sequences of ultrasound images of the heart showing the direction of the original velocity. Doing this, it is possible to calculate the original velocity in the marked direction. Both the recorded and corrected velocities have been used for calculating strain, in order to compare the two. Apical ultrasound images have been recorded on a sample of 18 normal individuals. The corrected velocities are on the average less than 5% higher than the recorded ones, and the effect on the derived variable strain is even less, so we suggest that the correction can be omitted when recording tissue velocities through an apical window.