Optimized glutamate detection at 3T.
OBJECTIVE
To identify the pulse sequence and acquisition parameters that result in the most accurate and repeatable measurements of glutamate (Glu) concentration in the brain at 3T.


METHODS
Simulations were performed to compare the accuracy and repeatability of 11 pulse sequences and acquisition parameters, within four general classes (PRESS, STEAM, Carr-Purcell PRESS [CPRESS] and TE averaged PRESS [JPRESS]), the majority of which were previously suggested as optimal for Glu detection. Three of the simulated acquisitions were implemented in a clinical scanner and measures of repeatability in vivo were compared to their simulated values.


RESULTS
Good agreement was demonstrated between simulated and experimentally determined measures of repeatability. Among the acquisitions considered, a CPRESS sequence with minimal echo time, together with, possibly, a short TE PRESS sequence, result in the most repeatable within session Glu measurements, while slightly overestimating the Glu concentration. Excellent accuracy is demonstrated by the simulations for a JPRESS sequence, at the expense of lower repeatability than optimal PRESS or CPRESS sequences.


CONCLUSIONS
Further proof of concept is presented toward validation of a simulation approach to understand pulse sequence performance in measuring the concentration of a given metabolite. Improved within session Glu measurement repeatability is predicted for CPRESS and demonstrated in vivo.
GE Global Research Center, Niskayuna, New York 12309, USA. hancu@crd.ge.com
Ileana
I
Hancu
D000328:Adult; D000465:Algorithms; D001921:Brain / Q000378:metabolism / Q000473:pathology; D001931:Brain Mapping / Q000379:methods*; D003198:Computer Simulation; D003287:Contrast Media / Q000494:pharmacology*; D018698:Glutamic Acid / Q000737:chemistry / Q000494:pharmacology*; D006801:Humans; D009682:Magnetic Resonance Spectroscopy / Q000295:instrumentation / Q000379:methods*; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D013997:Time Factors
D003287:Contrast Media; D018698:Glutamic Acid