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
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.