Optimal Sampling for 3D Projection Reconstruction Imaging

Introduction Projection reconstruction (PR) has received attention recently for several reasons: (1) it uses very short echo times (TEs), (2) spatial resolution is determined by readout resolution, and (3) it significantly oversamples the center of k-space. Short TE allows for rapid acquisition, imaging short T2 species and reduced motion and flow artifacts. All regions inside the radius satisfying the Nyquist criterion are oversampled with the area around the origin being most oversampled. Oversampling the region near the origin is advantageous because this area contains most of the energy in k-space. Investigators have shown that in 2D angular undersampling by a factor of up to sixteen times yields acceptable results [1]. 2D acquisition planes have been stacked to form a pseudo-3D PR sequence, with acceptable results found undersampling by factors up to eight [2]. Recently, 3D PR was demonstrated using VIPR where undersample rates up to 100 might be possible [3]. In this paper, 2D, psuedo-3D and 3D k-space trajectories (Figure 1) are compared in terms of alias free FOV.