ABSTRACT
School-age children are in a specific development stage corresponding to juvenility, when the white matter of the brain experiences ongoing maturation. Diffusion-weighted magnetic resonance imaging (DWI), especially diffusion tensor imaging (DTI), is extensively used to characterize the maturation by assessing white matter properties in vivo. In the analysis of DWI data, spatial normalization is crucial for conducting inter-subject analyses or linking the individual space with the reference space. Using tensor-based registration with an appropriate diffusion tensor template presents high accuracy regarding spatial normalization. However, there is a lack of a standardized diffusion tensor template dedicated to school-age children with ongoing brain development. Here, we established the school-age children diffusion tensor (SACT) template by optimizing tensor reorientation on high-quality DTI data from a large sample of cognitively normal participants aged 6-12 years. With an age-balanced design, the SACT template represented the entire age range well by showing high similarity to the age-specific templates. Compared with the tensor template of adults, the SACT template revealed significantly higher spatial normalization accuracy and inter-subject coherence upon evaluation of subjects in two different datasets of school-age children. A practical application regarding the age associations with the normalized DTI-derived data was conducted to further compare the SACT template and the adult template. Although similar spatial patterns were found, the SACT template showed significant effects on the distributions of the statistical results, which may be related to the performance of spatial normalization. Looking forward, the SACT template could contribute to future studies of white matter development in both healthy and clinical populations. The SACT template is publicly available now ( https://figshare.com/articles/dataset/SACT_template/14071283 ).
ABSTRACT
Objective To explore the effect of right median nerve stimulation ( RMNS) on brain function in healthy subjects . Methods Twenty-eight healthy volunteers were selected as the study′s subjects. RMNS was admin-istered as a task stimulation in a wake-up therapy mode. The subjects were given 30 seconds of stimulation followed by 30 seconds of rest, repeated for 6 times as the block experiment designed, and functional magnetic resonance imaging (fMRI) was performed simultaneously with the task stimulation . The brain activation was analyzed using SPM 12 soft-ware. Results The fMRI showed that RMNS activated primarily the left M1, the premotor cortex (PMC), the bilater-al primary and secondary somatosensory cortexes (S1 and S2), and the left insular lobe. Compared with the resting state, the intensity of BOLD signal in the above activated brain areas changed significantly in RMNS wake-up stimula-tion mode. Conclusion Stimulation of the right median nerve can stimulate the local cerebral cortex and produce a certain wake-up effect by activating the right brain areas related to the motor and sensory functioning of the hand.
ABSTRACT
Objective To investigate the value of 3D pseudo-continuous arterial spin labeling (3D-pCASL) magnetic resonance perfusion technique in evaluating posterior circulation ischemia (PCI) of the elderly beyond 80 years old and to offer the evidence of PCI of the elderly for clinical diagnosis. Methods Totally 53 male subjects older than 80 years were recruited in this study,including 20 subjects with clinically diagnosed PCI and 33 normal subjects. All the subjects underwent routine brain magnetic resonance imaging and 3D-pCASL sequence on a 3.0T magnetic resonance imaging system with 8 channel brain coil. Two post-labeling delay (PLD) time (PLD=1525 ms and PLD=2525 ms) of 3D-pCASL were used in this study to increase the accuracy of cerebral blood flow (CBF) change of posterior circulation region. We used SPM12 software to measure mean CBF values of bilateral occipital lobes and bilateral cerebellums. Independent sample t-test and rank-sum test were performed to evaluate the difference of CBF changes of anterior circulation and posterior circulation in two groups at two PLD time,the difference of CBF changes of bilateral occipital lobes and bilateral cerebellums in two groups of two PLD time,and the difference of increment of CBF between two PLD interval between two groups. Results In case group,the CBF value of the anterior circulation was significantly higher than that of posterior circulation at both two PLD time points (PLD=1525 ms and PLD=2525 ms)(P=0.000,P=0.000);in control group,the CBF value of the anterior circulation was significantly higher than that of the posterior circulation only at PLD=1525ms (P=0.025). The CBF values at bilateral occipital lobes and bilateral cerebellums at two PLD time points (PLD=1525 ms and PLD=2525 ms) were significantly higher in case group than in control group(P=0.003,P=0.002,P=0.000,P=0.001,P=0.000,P=0.001,P=0.002,P=0.014,respectively). Compared with the control group,the difference was statistically significant in bilateral occipital lobes and cerebellums with a smaller △CBF between two PLD interval in case group (P=0.004,P=0.001,P=0.001,P=0.025). Conclusion Multiple PLD time points need to be used in 3D-pCASL in diagnosing PCI of the elderly because the posterior circulation is slow in these patients. 3D-pCASL technique is sensitive in detecting decreased CBF in posterior circulation and therefore can be used to predict posterior circulation stroke in the elderly.
ABSTRACT
Objective To investigate the brain metabolic changes and evaluate their spatial distributions after traumatic axonal injury (TAI)in rats by using proton magnetic resonance spectroscopy(1H-MRS).Methods The TAI model was made by subjecting the head of the rats to the linear and angular accelerations.The multi-voxel MRS was employed to detect the tissue metabolic state at the levels of hippocampus-caudate and pons prior to injury and at 24 hours after injury.The alterations of NAA/Cr,NAA/Cho and Cho/Cr values as well as the spatial distribution of NAA/Cr reduction were accessed. Immunohistochemical staining for β-APP was used to observe the injured axons. Results A siguificantdecrease in NAA/Cr and NAA/Cho(P<0.05)and subtle increase in Cho/Cr(P>0.05)were observed in rats at 24 hours after TAI in comparison to the pre-injury levels.Notable decrease in NAA/Cr value was observed in the areas including the brain stem,hippocampus,internal capsule,corpus callosum and thalamus,where axonal injuries were confirmed by the histological examination. Conclusion Metabolic imbalances Occur in the brains of rats with TAI.with notable changes in the brain stem and the hippocampus.