Three-dimensional echo-planar MR spectroscopic imaging at short echo times in the human brain.
OBJECTIVE
To demonstrate the feasibility of three-dimensional echo-planar spectroscopic imaging (EPSI) at short echo time (13 msec) with a conventional clinical imager in the human brain.


METHODS
Periodic inversions of a readout gradient were used during data acquisition to simultaneously encode chemical shift and one spatial dimension in one excitation. Aliasing artifacts were avoided with a modified acquisition-and-processing method based on oversampling. A double outer-volume suppression technique that adapts to the ovoid brain shape was used to strongly reduce extracranial lipid resonances.


RESULTS
Three-dimensional spatial encoding in vivo of eight sections with 32 x 32 voxels each (0.75 cm3) was performed in 34 minutes with four signal averages. The spectral resolution and signal-to-noise ratio (S/N) of resonances of inositol, choline, creatine, glutamate and glutamine, and N-acetyl aspartate were consistent with those previously recorded with conventional phase encoding.


CONCLUSIONS
EPSI substantially reduces acquisition time for three-dimensional spatial encoding and yields a spectral quality similar to that obtained with conventional techniques without affecting the S/N per unit time and unit volume.
Posse
S
S
Department of Diagnostic Radiology, National Institutes of Health, Bethesda, MD 20892.
DeCarli
C
C
Le Bihan
D
D
D001224:Aspartic Acid / Q000031:analogs & derivatives / Q000032:analysis; D001921:Brain / Q000033:anatomy & histology; D001923:Brain Chemistry; D002794:Choline / Q000032:analysis; D003401:Creatine / Q000032:analysis; D017352:Echo-Planar Imaging / Q000379:methods; D005971:Glutamates / Q000032:analysis; D006801:Humans; D007294:Inositol / Q000032:analysis; D008279:Magnetic Resonance Imaging; D009682:Magnetic Resonance Spectroscopy
D005971:Glutamates; D001224:Aspartic Acid; D007294:Inositol; C000179:N-acetylaspartate; D003401:Creatine; D002794:Choline