Optimal gradient waveform design for projection imaging and projection reconstruction echoplanar spectroscopic imaging

Authors
Citation
Jm. Star-lack, Optimal gradient waveform design for projection imaging and projection reconstruction echoplanar spectroscopic imaging, MAGN RES M, 41(4), 1999, pp. 664-675
Citations number
39
Categorie Soggetti
Radiology ,Nuclear Medicine & Imaging","Medical Research Diagnosis & Treatment
Journal title
MAGNETIC RESONANCE IN MEDICINE
ISSN journal
07403194 → ACNP
Volume
41
Issue
4
Year of publication
1999
Pages
664 - 675
Database
ISI
SICI code
0740-3194(199904)41:4<664:OGWDFP>2.0.ZU;2-F
Abstract
The use of modulated B-0 projection gradient waveforms is proposed for magn etic resonance imaging (MRI) and magnetic resonance spectroscopic imaging ( MRSI) to shape the k-space sampling density function to match the profile o f an applied reconstruction window function. This allows for a time-efficie nt means of maximizing the signal-to-noise ratio when, for example, a low-p ass spatial filter, designed to reduce k-space truncation artifacts and cor responding point-spread function sidelobe energies, is implemented. Both th e two-dimensional (2D) and 3D cases are investigated. To create the project ion gradient waveforms, a design method is developed that uses nonlinear co nstrained optimization (NLCO) to minimize the variance of the reconstructio n noise. The design is subject to both equality and inequality constraints, which include the maximum gradient magnitude and slew rate. It is shown th at NLCO can also be applied to twisting the projection trajectories for pur poses of reducing the data acquisition time while still maintaining the des ired sampling density. Applications to H-1 MRSI are investigated via simula tions. Advantages and limitations of the new sampling schemes are discussed . (C) 1999 Wiley-Liss, Inc.