Structure of the water resonance in small voxels in rat brain detected with high spectral and spatial resolution MRI.
OBJECTIVE
To acquire high spectral and spatial resolution (HiSS) MR images of the water resonance in rat brain, evaluate the lineshape of the water resonance in small voxels, and compare images derived from HiSS data with conventional images.


METHODS
Spectroscopic images of rat brain were obtained at 4.7 Tesla using phase encoding gradients only. Spectral resolution in each voxel was approximately 8 Hz and bandwidth was 1,000 Hz. Spatial resolution was approximately 250 microns in 1-mm slices. Images were synthesized to show the water signal integral, peak height, linewidth, resonance frequency, and asymmetry.


RESULTS
Two or more resolved components of the water resonance were detected in approximately 14% +/- 6% of voxels in the brains of eight rats. The water resonances in approximately 20% +/- 10% of voxels (n = 8) were highly asymmetric. Images with intensity proportional to water signal peak height, T(2)*, or to selected components of the water resonance showed features that were not evident in conventional images.


CONCLUSIONS
The complexity of the water signal reflects the anatomy and physiology of the sub-voxelar environment, and may be a useful source of image contrast. HiSS imaging of brain provides accurate anatomic information, and may improve image contrast and delineation of subtle anatomic features.
Fan
Xiaobing
X
Department of Radiology, University of Chicago, Chicago, Illinois 60637, USA.
Du
Weiliang
W
MacEneaney
Peter
P
Zamora
Marta
M
Karczmar
Gregory
G
D000818:Animals; D001834:Body Water / Q000378:metabolism*; D001921:Brain / Q000378:metabolism*; D001923:Brain Chemistry; D017352:Echo-Planar Imaging; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D051381:Rats; D011916:Rats, Inbred F344