Blood flow measurement using variable velocity encoding in the RR interval.

Velocity-encoded phase imaging using asynchronous gating requires input of a velocity encoding value to set the velocity sensitivity of the pulse sequence. The raw data interpolation and reconstruction scheme that the pulse sequence uses forces the encoding value to be constant throughout the RR interval. The sequence and the raw data interpolation scheme were modified to allow two velocity encodings during the RR interval. Two-hundred cm/s encoding was used in systole, and 30 cm/s in diastole. Changing the encoding in diastole significantly improved the accuracy and precision of ascending aorta flow measurements.