Efficient k-space sampling by density-weighted phase-encoding.
Acquisition-weighting improves the localization of MRI experiments. An approach to acquisition-weighting in a purely phase-encoded experiment is presented that is based on a variation of the sampling density in k-space. In contrast to conventional imaging or to accumulation-weighting, where k-space is sampled with uniform increments, density-weighting varies the distance between neighboring sampling points Deltak to approximate a given radial weighting function. A fast, noniterative algorithm has been developed to calculate the sampling matrix in one, two, and three dimensions from a radial weighting function w(k), the desired number of scans NA(tot) and the nominal spatial resolution Deltax(nom). Density-weighted phase-encoding combines the improved shape of the spatial response function and the high SNR of acquisition-weighting with an extended field of view. The artifact energy that results from aliasing due to a small field of view is substantially reduced. The properties of density-weighting are compared to uniform and to accumulation-weighted phase-encoding in simulations and experiments. Density-weighted (31)P 3D chemical shift imaging of the human heart is shown which demonstrates the superior performance of density-weighted metabolic imaging.
Greiser
Andreas
A
University of Würzburg, Department of Biophysics, Würzburg, Germany.
von Kienlin
Markus
M
D006321:Heart / Q000033:anatomy & histology; D006801:Humans; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D019047:Phantoms, Imaging