Gradient echo time dependence and quantitative parameter maps for somatosensory activation in rats at 7 T.
The dependence of functional magnetic resonance imaging (MRI) contrast on the gradient echo time TE in T2*-weighted blood oxygenation level-dependent (BOLD) fast low-angle shot (FLASH) imaging has been studied at 7 T for electrical forepaw stimulation in alpha-chloralose anesthetized rats. The observed variation of both the activation signal intensity and spatial pattern with echo time TE, resulting from the regional heterogeneity of T2*, was assessed by the calculation of quantitative T2* and quantitative STE = 0 maps, the latter representing the back-extrapolated signal intensity for TE = 0. The subsequently determined T2* and STE = 0 activation maps allowed a pixelwise separation of true BOLD from inflow contributions to forepaw stimulation-induced signal change in the somatosensory cortex of rat brain. For functional activation experiments performed with one single echo time the prior measurement of a quantitative T2* map is recommended as minimum further information to judge the intensity and the regional pattern of the resulting activation maps.
Department of Experimental Neurology, Max-Planck-Institute for Neurological Research, Cologne, Germany. mathias@mpin-koeln.mpg.de
M
M
Grüne
F
F
Pillekamp
W
W
Schwindt
M
M
Hoehn
D000344:Afferent Pathways / Q000502:physiology; D000818:Animals; D001143:Arousal / Q000502:physiology*; D001931:Brain Mapping / Q000295:instrumentation; D017352:Echo-Planar Imaging / Q000295:instrumentation*; D005552:Forelimb / Q000294:innervation; D007091:Image Processing, Computer-Assisted / Q000295:instrumentation*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D008297:Male; D010100:Oxygen / Q000097:blood*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013003:Somatosensory Cortex / Q000502:physiology*
D010100:Oxygen