Undersampled projection reconstruction applied to MR angiography

Undersampled projection reconstruction (PR) is investigated as an alternati ve method for MRA (MR angiography). In conventional 3D Fourier transform (F T) MRA, resolution in the phase-encoding direction is proportional to acqui sition time. Since the PR resolution in all directions is determined by the readout resolution, independent of the number of projections (N-p), high r esolution can be generated rapidly. However, artifacts increase for reduced N-p. In X-ray CT, undersampling artifacts from bright objects like bone ca n dominate other tissue. In MRA, where bright, contrast-filled vessels domi nate, artifacts are often acceptable and the greater resolution per unit ti me provided by undersampled PR can be realized. The resolution increase is limited by SNR reduction associated with reduced voxel size. The hybrid 3D sequence acquires fractional echo projections in the k(x)-k(y) plane and ph ase encodings in k(z). PR resolution and artifact characteristics are demon strated in a phantom and in contrast-enhanced volunteer studies. Magn Reson Med 43:91-101,2000, (C) 2000 Wiley-Liss, Inc.