Abstract:
Introduction: The measurement of peak velocities, velocity time integrals and flow is vital for accurate classification of aortic stenosis (AS). Phase contrast (PC) magnetic resonance (MR) is a potential alternative to the current clinical standard, Doppler ultrasound, but its accuracy and reliability in the moderate-severe AS patients with very high velocity turbulent stenotic jets has been questioned. Accurate PC velocity measurements rely on all the spins in a voxel to be moving with the same velocity. When the voxel’s velocity range becomes too large, signal loss is seen in the magnitude image and the mean velocity estimate becomes unreliable. Many flow mechanisms inherent in a high velocity stenotic jet (e.g. accelerations, turbulence, shear) act to worsen this intravoxel dephasing. We have previously shown that these effects can be reduced by shortening the echo time (TE) [1]; however, the extent that the TE can be shortened is limited; therefore we aimed to develop and evaluate a PC implementation of an ultra short TE (PC-UTE) sequence that: a) minimises TE; b) measures velocity over the shortest possible time window; and c) reduces intravoxel dephasing and other errors associated with velocity measurement.
