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Background: Heterogeneity of arterial transit time due to cerebral artery steno-occlusive lesions hampers accurate regional cerebral blood flow measurement by arterial spin labeling (ASL). Purpose: To assess the feasibility of regional cerebral blood flow measurement by ASL with multiple-delay time sampling in patients with steno-occlusive diseases by comparing with positron emission tomography (PET), and to determine whether regional arterial transit time measured by this ASL technique is correlated with regional mean transit time, a PET index of perfusion pressure. Material and Methods: Sixteen patients with steno-occlusive diseases received both ASL and (15)O-PET. The mean regional cerebral blood flow measured by ASL and PET, regional arterial transit time by ASL, and regional mean transit time by PET were obtained by a region-of-interest analysis. Correlation between regional cerebral blood flow by ASL and that by PET, and correlation between regional arterial transit time by ASL and regional mean transit time by PET were tested using Pearson's correlation coefficient for both absolute and relative values. A multivariate regression analysis was performed to test whether regional arterial transit time by ASL was a significant contributor in modeling regional mean transit time by PET after controlling the effect of regional cerebral blood flow by ASL. Results: A significant positive correlation was found between regional cerebral blood flow by ASL and that by PET for both absolute (r = 0.520, P < 0.0001) and relative (r = 0.691, P < 0.0001) values. A significant positive correlation was found between regional arterial transit time by ASL and regional mean transit time by PET both for absolute (r = 0.369, P = 0.0002) and relative (r = 0.443, P < 0.0001) values. The regression analysis revealed that regional arterial transit time by ASL was a significant contributor in modeling regional mean transit time by PET after controlling regional cerebral blood flow by ASL (P = 0.0011). Conclusion: The feasibility of regional cerebral blood flow measurement using ASL with multiple-delay time sampling was confirmed in patients with cerebral artery steno-occlusive diseases. Moreover, it was suggested that mapping of regional arterial transit time has the potential to detect hemodynamic impairment. [ABSTRACT FROM AUTHOR]

Our purpose was to reveal potential regional variations in water molecular diffusivity within each cerebral hemisphere and across the right and left hemispheres. Diffusion-weighted images of 44 healthy right-handed adult male subjects were obtained using a diffusion tensor imaging sequence. Mean diffusivity (MD) values in subcortical white matter (WM) within 39 regions in each hemisphere were measured using an automated method. Intrahemispheric comparisons of MDs in subcortical WM were performed among six brain regions (frontal, parietal, occipital and temporal lobes and pre- and postcentral gyri). Interhemispheric comparisons of MDs were performed between the right and left counterparts of the 39 regions. In both hemispheres, diffusivity in the precentral gyrus was lower than those in other regions, while diffusivity in the parietal lobe was higher than others. MD asymmetry in which the left was lower than the right was found in the parietal lobe, middle occipital gyrus, and medial and orbital aspects of the frontal lobe. The converse asymmetry was revealed in the frontal operculum, supplementary motor cortex, temporal lobe, limbic cortices, precuneus and cuneus. Our results revealed significant intra- and interhemispheric regional variations in MD in subcortical WM, which may be related to different densities of axons and myelin sheaths. [ABSTRACT FROM AUTHOR]

The purpose of this study was to determine whether arterial spin labelling (ASL) at 3-T MR imaging can be used to discriminate individuals with Alzheimer's disease (AD) from cognitively normal subjects. Twenty AD patients and 23 cognitively normal control subjects were studied using ASL on a 3-T MR imager. Absolute regional cerebral blood flow (rCBF) maps were calculated. In addition, normalized rCBF maps were obtained using CBF in the sensorimotor cortex for normalization. A voxel-wise comparison of these rCBF maps between the AD and control groups was performed using the two-sample t test. Individuals with AD were discriminated from control subjects based on mean rCBF values within a region-of-interest defined by the t test, and the discriminating performance was evaluated by the receiver operating characteristic (ROC) analysis. Comparisons of both absolute and normalized rCBF maps revealed areas of significant hypoperfusion caused by the effects of AD in the bilateral precunei and posterior cingulate gyri. ROC analyses resulted in area under the curve (AUC) values of 0.861 to 0.877 for absolute and 0.910 to 0.932 for normalized rCBF. Our results suggest that ASL at 3-T MR imaging can be used to help discriminate individuals with AD from normal subjects. [ABSTRACT FROM AUTHOR]