The measurement of time-averaged flow by magnetic resonance imaging using continuous acquisition in the carotid arteries and its comparison with Doppler ultrasound.

A continuous acquisition method was used to measure the time-averaged flow in the carotid arteries of 10 normal volunteers, using an interleaved flow-sensitive and flow-compensated field echo sequence on a 1.5 T magnetic resonance (MR) system. Validation of the sequence and technique was performed using a pulsatile rotating phantom. The measured flow rates for the common carotid arteries were compared with Doppler ultrasound values obtained immediately after the MR measurement using a Duplex scanner. The correlation (r = 0.52, P less than 0.01) was significant with data spread accounted for by the inherent errors of both techniques. The difference between time-averaged flow measured by MR and Doppler ultrasound was 1.9%. Short-term reproducibility of each technique was assessed by consecutive measurements with values of 6.8% and 6.6% respectively for MR and Doppler; measurements after a 2 - 4 week interval gave a long-term reproducibility of 11.8% and 9.8% respectively. The advantages of continuous acquisition make the method suitable for non-invasive flow measurements, particularly for vessels that are not accessible to ultrasound.