Combination of MRI hippocampal volumetry and arterial spin labeling MR perfusion at 3-Tesla improves the efficacy in discriminating Alzheimer's disease from cognitively normal elderly adults.

BACKGROUND: Structural magnetic resonance imaging has been employed for evaluation of medial temporal atrophy in patients with Alzheimer's disease (AD). Arterial spin labeling (ASL) technique could detect cerebral perfusion abnormalities in AD. OBJECTIVE: We hypothesized that combination of hippocampal volumetry and cerebral blood flow yield higher accuracy than either method alone in discriminating AD patients from cognitively normal elderly adults. MATERIALS AND METHODS: 13 AD patients and 15 healthy controls were studied using a 3-tesla scanner. Standardized T1W 3D volumetric Fast Field Echo and QUASAR ASL sequences were employed for cerebral volumetry and perfusion respectively. Manual Right and left hippocampal volumetry was performed manually by ANALYZE software, with total intracranial volume normalization. ASL data were analyzed by institutional specially-design software to calculate cerebral blood flow of region-of-interests placed at the middle and posterior cingulate gyri. RESULTS: Right and left hippocampal volumes and middle and posterior cingulate gyri cerebral blood flows were significantly lower in the patients than in the controls (independent-samples t-tests, p < 0.05), and prediction accuracies of 89.3%, 82.1%, 75.0% and 71.4% were achieved for each of the above parameters, respectively. In distinguishing patients from controls using corresponding optimized cut-off values, various combinations of these parameters were used to create the Receiver Operating Characteristic curves. The highest area under curve value was 0.944, by combining cerebral blood flow at the middle cingulate gyrus, normalized right and left hippocampal volumes. CONCLUSIONS: A 'one-stop-shop' magnetic resonance study of combined hippocampal volumetry and cerebral perfusion has improved efficacy in discriminating AD patients from cognitively normal elderly adults.

Metabolic changes in the anterior and posterior cingulate cortices of the normal aging brain: proton magnetic resonance spectroscopy study at 3 T.

Magnetic resonance spectroscopy (MRS) can explore aging at a molecular level. In this study, we investigated the relationships between regional concentrations of metabolites (such as choline, creatine, myo-inositol, and N-acetyl-aspartate) and normal aging in 30 cognitively normal subjects (15 women and 15 men, age range 22-82, mean = 49.9 ± 18.3 years) using quantitative proton magnetic resonance spectroscopy. All MR scans were performed using a 3 T scanner. Point resolved spectroscopy was used as the volume selection method for the region-of-interest and the excitation method for water suppression. Single voxel spectroscopy with short echo time of 39 ms and repetition time of 2,000 ms was employed. Single voxels were placed in the limbic regions, i.e., anterior cingulate cortex (ACC), posterior cingulate cortex (PCC), and left and right hippocampi. Cerebrospinal fluid normalization and T1 and T2 correction factors were implemented in the calculation of absolute metabolite concentrations. A standardized T1W 3D volumetric fast field echo and axial T2-weighted fast spin-echo images were also acquired. Our results showed significant positive correlation of choline (r = 0.545, p = 0.002), creatine (r = 0.571, p = 0.001), and N-acetyl-aspartate (r = 0.674, p < 0.001) in the ACC; choline (r = 0.614, p < 0.001), creatine (r = 0.670, p < 0.001), and N-acetyl-aspartate (r = 0.528, p = 0.003) in the PCC; and NAA (r = 0.409, p = 0.025) in the left hippocampus, with age. No significant gender effect on metabolite concentrations was found. In aging, increases in choline and creatine might suggest glial proliferation, and an increase in N-acetyl-aspartate might indicate neuronal hypertrophy. Such findings highlight the metabolic changes of ACC and PCC with age, which could be compensatory to an increased energy demand coupled with a lower cerebral blood flow.

Pilot study on evaluation of any correlation between MR perfusion (Ktrans) and diffusion (apparent diffusion coefficient) parameters in brain tumors at 3 Tesla.

PURPOSE: To assess any correlation of volume transfer constant (Ktrans) with apparent diffusion coefficient (ADC) in different brain tumor types at 3 T magnetic resonance (MR) imaging. MATERIALS AND METHODS: Thirteen patients with brain tumors (8 men, 5 women; mean age 54.6±17.7 years) were enrolled in this retrospective study. All patients underwent dynamic contrast-enhanced T1-weighted MR perfusion and diffusion-weighted imaging using a 3 T scanner. Ktrans was estimated by specially designed software. For each tumor, regions of interest (ROIs) were manually selected on corresponding Ktrans and ADC maps. Pearson correlation coefficients were obtained for maximum, mean and minimum values of Ktrans and ADC of all ROIs. Based on clinicopathologic results, the final diagnoses of patients were glioblastoma multiforme (3), low-grade to anaplastic gliomas (4), meningiomas (3) and metastatic tumors (3). RESULTS: Ktrans(max) values were significantly inversely correlated with ADC(min) values (r=-0.536, P<0.001) and ADC(mean) values (r=-0.465, P<0.001). Ktrans(mean) and Ktrans(min) values were significantly inversely correlated with ADC(mean) (r=-0.228, P=0.038) and ADC(max) values (r=-0.355, P=0.001), respectively. CONCLUSION: We found that irrespective of brain tumor type, there is an inverse correlation between ADC and Ktrans. Our findings highlight an intricate relationship between vascular permeability and the tumor microenvironment, probably modulating and/or interacting with changes such as increased cellularity, ischemic insult and varying extracellular matrix composition.

Quantitative assessment of the cervical spinal cord damage in neuromyelitis optica using diffusion tensor imaging at 3 Tesla.

PURPOSE: To investigate whether quantitative MRI measures of cervical spinal cord white matter (WM) using diffusion tensor imaging (DTI) in neuromyelitis optica (NMO) differed from controls and correlated with clinical disability. MATERIALS AND METHODS: Ten referred patients and 12 healthy volunteers were imaged on a 3 Tesla scanner and patients were clinically assessed on the Expanded Disability Status Scale (EDSS). Two raters quantified DTI-derived indices from all participants, including fractional anisotropy (FA), mean diffusivity (MD), parallel diffusivity (lambda[parallel]) and perpendicular diffusivity (lambda[perpendicular]) at C1-C6 for lateral and dorsal columns. After the inter-rater reliability test, univariate correlations between DTI measures and disability were assessed using the Spearman's rho correlation coefficient. Multiple regression analysis was performed to investigate which DTI measures independently correlated with the clinical score. RESULTS: Statistical test results indicated high reliability of all DTI measurements between two raters. NMO patients showed reduced FA, increased MD and lambda[perpendicular] compared with controls while lambda[parallel] did not show any significant difference. The former three DTI metrics also showed significant correlations with disability scores, and especially FA was found to be sensitive to mild NMO (EDSS ≤ 3) CONCLUSION: FA is a potentially useful quantitative biomarker of otherwise normal appearing WM damage in NMO. Such damage is associated with clinical disability.

Efficacy of voxel-based morphometry with DARTEL and standard registration as imaging biomarkers in Alzheimer's disease patients and cognitively normal older adults at 3.0 Tesla MR imaging.

Quantitative MRI of the hippocampus has been increasingly employed as a biomarker in Alzheimer's disease (AD). We compare voxel-based morphometry (VBM) standard and DARTEL registration with manual hippocampal volumetry in AD patients and cognitively normal older adults. Participants were 20 cognitively normal elderly subjects and 19 AD patients who met the criteria of probable AD according to NINCDS-ADRDA. Bilateral manual hippocampal volumetry was conducted alongside VBM of hippocampal regions-of-interest (ROIs) generated with standard and DARTEL registration using hippocampal masks and total intracranial volume normalization. All normalized hippocampal measurements showed significant reduction (20­30%; p < 0.001) in AD compared to controls. Logistic regression analysis also showed significant effects (odds ratios ranged from 88.2% to 94.0%) of all normalized measurements in predicting AD incidence after adjusting for age, gender, and education. The overall prediction accuracies of manual RH and LH volumes, standard RH-ROI and LH-ROI VBM, DARTEL RH-ROI, and LH-ROI VBM were 87.2%, 84.6%, 87.2%, 76.9%, 87.2%, and 87.2%, respectively. As imaging biomarkers, VBM with DARTEL and standard registration have similarly high efficacies as manual hippocampal volumetry in discriminating AD from cognitively normal elderly adults.

Computed tomography evaluation of intracranial atherosclerosis in Chinese patients with transient ischemic attack or minor ischemic stroke--its distribution and association with vascular risk factors.

OBJECTIVES: Intracranial atherosclerosis has been suggested to be common in Asians. We apply a semi-quantitative CT scoring system to evaluate the degree of intracranial atherosclerotic calcification and determine its distribution, severity, and the associated risk factors. The clinical outcome of these patients after a 3-year follow-up was also evaluated. METHODS: Sixty consecutive patients diagnosed clinically to have either a transient ischemic attack (TIA) or minor ischemic stroke and underwent early computed tomographic angiography (CTA) were included into the prospective study. Two radiologists evaluated the axial CTA images for any calcification in the precavernous, cavernous and postcavernous segments of intracranial internal carotid artery (ICA), anterior, middle, and posterior cerebral as well as vertebrobasilar arteries, based on a standard CT scoring system for extent (0-4) and thickness (0-4). The composite CT score for extent and thickness of these vascular segments or vessels were recorded for all patients. The worst site (highest composite score) was chosen as the marker of the degree of intracranial atherosclerosis of each patient. The patients were then classified into mild, moderate, and severe groups, according to a composite CT score of 0-2, 3-5, and 6-8, respectively. These findings were gathered with clinical parameters and outcome after a 3-year follow-up period and corresponding statistical analyses were conducted. RESULTS: The most severely affected vessel was found to be intracranial internal carotid arteries, and severe, moderate, and mild atherosclerosis were present in 16 (26.67%), 30 (50%), and 14 (23.33%) patients, respectively. Using multiple logistic regression analysis, diabetes mellitus (odds ratio = 10.6, P value = .004), and age (odds ratio = 1.07, P value = .02) were found to be significant risk factors for severe intracranial atherosclerosis. Two patients in the severe group, 3 patients in the moderate group, and 1 patient in the mild group were found to have stroke or TIA after a 3-year follow-up, but there was no significant difference among the 3 groups. CONCLUSION: Significant intracranial atherosclerosis as determined by severe CT calcification was common in a cohort of Chinese patients with TIA and minor stroke. Age and diabetes mellitus were independent significant risk factors, and this CT calcification score might serve as an early indicator of intracranial atherosclerotic disease.