AN ASYMMETRIC SLICE PROFILE - SPATIAL ALTERATION OF FLOW SIGNAL RESPONSE IN 3D TIME-OF-FLIGHT NMR ANGIOGRAPHY

We introduce an asymmetric slice profile technique, which alters the s patial response of the flow signal in 3D time-of-flight NMR angiograph y. By gradually increasing the flip angle from the inflow to the outfl ow portions of the slab, the inflow refreshment effect is distributed over a wide slab thickness. The asymmetric slice profile is simply pro duced by using a Gaussian RF excitation with an overlapping presaturat ion. The spatial distribution of steady flow signal in a phantom study demonstrated an essential agreement with a numerical simulation. 3D t ime-of-flight NMR angiography of volunteers' heads using this techniqu e provided a smooth vascular depiction over a wide slab thickness.