Complex flow, such as those associated with stenoses involves velocities, accelerations, and higher order motion moments, and is difficult to image by MRI. This is because spins flowing in the magnetic fields applied for imaging undergo dephasing and result in signal loss. Gradient moment nulling techniques compensate for velocities, but not acceleration and other higher order motions. We have developed a method to image and measure velocities in and near the turbulent jets produced by stenoses. The ultra-fast MR imaging technique, RUFIS (Rotating Ultra-Fast Imaging Sequence) that was developed in this Center has been used successfully to image """"""""turbulent puffs"""""""" and turbulent jets produced by a stenotic phantom. During the past year, we have extended our measurements to develop a method to measure flow velocities in and near the turbulent jets produced by stenoses. Velocity is encoded into the signal by a velocity encoding slice selection sequence applied prior to the RUFIS imaging sequence. Velocity encoded images are obtained for through-plane flow at the stenosos and at 1 cm upstream from it. Relative velocity contour maps with 0.67 mm resolution have been obtained for Reynolds numbers upto 2500.
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