Dynamic activity-induced manganese-dependent contrast magnetic resonance imaging (DAIM MRI).
Activity-induced manganese-dependent contrast (AIM) MRI is a hemodynamic-independent functional MRI method that used manganese ion as an MR-detectable contrast agent. In AIM, MnCl(2) is infused intra-arterially after the blood-brain barrier (BBB) is opened with a hyperosmolar agent. Upon functional stimulation of the brain, Mn(2+) accumulates in the active region(s) by entering active cells through voltage-gated Ca(2+) channels, causing local signal increases in T(1)-weighted images. The contrast of AIM MRI depends strongly on the depth of anesthesia, and the low levels used in somatosensory stimulation studies can lead to significant nonspecific accumulation of manganese ion throughout the brain. The purpose of this study was to produce an AIM functional map of somatosensory stimulation, which separates the stimulation-specific signal increase from the nonspecific activation due to light anesthesia. A dynamic AIM (DAIM) paradigm was developed, which used sequential MR scans during MnCl(2) infusion, prior to and following functional stimulation of the brain. Stimulation-specific functional maps were produced using time-course analysis. The new method was tested during glutamate administration and electric stimulation of the rat forepaw. It was shown that DAIM maps are better confined to the specific region of brain activated by somatosensory stimulation as compared to AIM MRI.
Aoki
Ichio
I
Department of Neurosurgery, Meiji University of Oriental Medicine, Kyoto, Japan. aoki@muom.meiji-u.ac.jp
Tanaka
Chuzo
C
Takegami
Tetsuro
T
Ebisu
Toshihiko
T
Umeda
Masahiro
M
Fukunaga
Masaki
M
Fukuda
Kohji
K
Silva
Afonso C
AC
Koretsky
Alan P
AP
Naruse
Shoji
S
D000704:Analysis of Variance; D000818:Animals; D001921:Brain / Q000033:anatomy & histology* / Q000502:physiology; D001931:Brain Mapping; D002712:Chlorides; D003287:Contrast Media; D004558:Electric Stimulation; D018698:Glutamic Acid; D007089:Image Enhancement / Q000379:methods*; D016014:Linear Models; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D017895:Manganese Compounds; D023421:Models, Animal; D011336:Probability; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D012680:Sensitivity and Specificity; D013003:Somatosensory Cortex / Q000473:pathology
D002712:Chlorides; D003287:Contrast Media; D017895:Manganese Compounds; D018698:Glutamic Acid; C025340:manganese chloride