Pseudo-Fourier imaging (PFI): a technique for spatial encoding in MRI

In magnetic resonance imaging (MRI), spatial discrimination is usually achieved with selective excitation and/or Fourier encoding. While these approaches are favorable in most situations, it is sometimes desirable to have an approach that takes advantage of both selective excitation and Fourier encoding. In this paper, we describe the theory and experimental results of a new technique, which we will call pseudo-Fourier imaging (PFI), that provides a flexible combination of both approaches. The technique is based on a windowed Fourier transform that expands the continuous object spatial distribution in terms of coherent states. A detailed description of the proposed technique is presented in this paper. The practical implementation of this technique is described and shown to be achieveable using a set of selective excitations combined with a number of Fourier encoding steps. Then, the signal-to-noise ratio of the new technique is derived to show that it can be varied at will anywhere in the range between the ratios for selective excitation and Fourier encoding. Finally, the experimental results of implementing the technique are presented and some potential applications of the technique such as volume imaging, dynamic imaging and magnetic resonance angiography are discussed. Index Terms - Fast imaging, Fourier imaging, MRI, selective excitation.