Multidimensional MR mapping of multiple components of velocity and acceleration by Fourier phase encoding with a small number of encoding steps

Previous studies have shown that the multi-step approach of velocity or acc eleration encoding is highly efficient in terms of the signal-to-noise rati o per unit time. This work describes a multidimensional extension of this m ethod for simultaneously measuring multiple components of velocity and acce leration with a few encoding steps. N flow dimensions were encoded with an No-matrix, obtained by combining the various flow-encoding gradients. The s mall matrix obtained with as few as two encoding steps can be extended by z ero-filling in all N dimensions and using ND-Fourier transformation to obta in the maximum of the resulting peak in the No-matrix, which gives simultan eously all the components of velocity and/or acceleration. The processing t ime was shortened by using a method of phase computation that gives the sam e precision as Fourier transformation, but is much faster. A rotating disk was used to show that the velocity-to-noise ratio increases with the number of dimensions acquired, demonstrating the efficiency of multidimensional f low measurements. The feasibility of the method is illustrated by 3D maps o f the myocardium velocity, and 2D measurement of velocity and acceleration in the ascending aorta - both obtained by multidimensional phase encoding i n volunteers. (C) 2000 Wiley-Liss, Inc.