Nmr fourier imaging from multiple echoes

Abstract

Fourier images based on multiple NMR echoes may be obtained using the method and apparatus disclosed. A sequence of pulses and gradients are applied to the object to be imaged. The pulses begin with an excitation pulse, which is followed by a series of refocusing pulses. In order to compensate for phase error in the refocusing pulses, the refocusing pulses are applied along alternating X and Y axes in the rotating frame of reference. The echoes are then coherently added to reserve phase information. Alternate echoes may be time reversed and their complex conjugate may be taken to permit coherent addition. Alternatively, the even echoes may be added separately from the odd echoes to produce separate data sets. The pulse and gradient switching sequence provides sign reversals such that any baseline component will be cancelled by the coherent addition. Before or after coherent addition, the echoes are transformed, and after forming a combined data set from a series of echo sequences, the combined data set is again transformed to produce an image of the object.