Three-dimensional spiral echo volume imaging

Abstract

Magnetic resonance imaging data of a volume of interest is collected by applying a radio frequency pulse (70, 96) and following the pulse with gradients applied along three axes (x,y,z). The gradients along x and y-axes are generally sinusoidal, which sinusoids increase and decrease in magnitude to define beat patterns of a common period. The period of the first and second gradients is an integer multiple of the gradient along the z-axis. In the embodiment of FIGS. 2A and 2B, the beats of the first and second gradients increase linearly and the third gradient oscillates in a linearly expanding generally sinusoidal pattern such that k-space is traversed by a trajectory that spirals around a series of spheres (50, 52, 54, 56, 58, 60) of progressively smaller radius. Blips or spikes (78) are preferably applied between each half cycle of the third gradient to step the trajectory to the radius of the next concentric sphere. In the embodiment of FIGS. 3A and 3B, the magnitude of the beats of the first and second gradients remain substantially constant and the gradient pulses along the third axis are applied generally between and at the mid-point of each beat such that the trajectory through k-space follows a series of parallel spirals lying along a cylinder. In the embodiment of FIGS. 4-4D, the beat patterns again increase linearly and the third gradient alternates polarity with each half beat such that the trajectory through k-space spirals around a series of concentric cones.