Faculty Bibliography

Prior postmortem studies have shown gray matter (GM) microstructural abnormalities in schizophrenia. However, few studies to date have examined GM microstructural integrity in schizophrenia in vivo. Here, we employed diffusion kurtosis imaging (DKI) to test for differences in GM microstructure in eighteen schizophrenia (SZ) patients versus nineteen healthy controls (HC). GM microstructure was characterized in each participant using DKI-derived metrics of mean kurtosis (MK) and mean diffusivity (MD). Individual T1-weighted images were used to create subject-specific cortically-labelled regions of interest (ROIs) of the four cortical lobes and sixty-eight cortical GM regions delineated by the Desikan-Killiany atlas, and to derive the associated cortical thickness and area measures. The derived ROIs were also registered to the diffusion space of each subject and used to generate region-specific mean MK and MD values. We additionally administered the Wisconsin Card Sorting Test (WCST), Stroop test, and Trail Making Test part B (Trails-B) to test the relationship between GM metrics and executive function in SZ. We found significantly increased MK and MD in SZ compared to HC participants in the temporal lobe, sub-lobar temporal cortical regions (fusiform, inferior temporal, middle temporal and temporal pole), and posterior cingulate cortex after correcting for multiple comparisons. Correlational analyses revealed significant associations of MK and MD with executive function scores derived from the WCST, Stroop, and Trails-B tests, along with an inverse relationship between MK and MD and cortical thickness and area. A hierarchical multiple linear regression analysis showed that up to 85% of the inter-subject variability in cognitive function in schizophrenia measured by the WCST could be explained by MK in combination with either GM thickness or area. MK and MD appear to be sensitive to GM microstructural pathology in schizophrenia and may provide useful biomarkers of abnormal cortical microstructure in this disorder.

BACKGROUND:There is growing interest in detecting cerebro-cerebellar circuits, which requires adequate blood oxygenation level dependent contrast and signal-to-noise ratio (SNR) throughout the brain. Although 7T scanners offer increased SNR, coverage of commercial head coils is currently limited to the cerebrum. PURPOSE/OBJECTIVE:To improve cerebellar functional MRI (fMRI) at 7T with high permittivity material (HPM) pads extending the sensitivity of a commercial coil. STUDY TYPE/METHODS:Simulations were used to determine HPM pad configuration and assess radiofrequency (RF) safety. In vivo experiments were performed to evaluate RF field distributions and SNR and assess improvements of cerebellar fMRI. SUBJECTS/METHODS:Eight healthy volunteers enrolled in a prospective motor fMRI study with and without HPM. FIELD STRENGTH/SEQUENCE/UNASSIGNED:Gradient echo (GRE) echo planar imaging for fMRI, turbo FLASH for flip angle mapping, GRE sequence for SNR maps, and T1 -weighted MPRAGE were acquired with and without HPM pads at 7T. ASSESSMENT/RESULTS:Field maps, SNR maps, and anatomical images were evaluated for coverage. Simulation results were used to assess SAR levels of the experiment. Activation data from fMRI experiments were compared with and without HPM pads. STATISTICAL TESTS: fMRI data were analyzed using FEAT FSL for each subject followed by group level analysis using paired t-test of acquisitions with and without HPM. RESULTS:Simulations showed 52% improvement in transmit efficiency in cerebellum with HPM and SAR levels well below recommended limits. Experiments showed 27% improvement in SNR in cerebellum and improvement in coverage on T1 -weighted images. fMRI showed greater cerebellar activation in individual subjects with the HPM pad present (Z > = 4), especially in inferior slices of cerebellum, with 59% average increase in number of activated voxels in the cerebellum. Group-level analysis showed improved functional activation (Z > = 2.3) in cerebellar regions with HPM pads without loss of measured activation elsewhere. DATA CONCLUSION/UNASSIGNED:HPM pads can improve cerebellar fMRI at 7T with a commonly-used head coil without compromising RF safety. LEVEL OF EVIDENCE/METHODS:2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2017.

BACKGROUND: Resting state fMRI (rsfMRI) is task independent mapping of individual brain function. Here we demonstrated the clinical feasibility of rsfMRI in patients with brain tumor. MATERIALS AND METHODS: Resting-state fMRI data from a total of 39 cases (32 primary brain tumor patients [8 tumors in sensorimotor cortices] and 7 normal healthy control cases) were analyzed based on independent component analysis (ICA). For each patient, ipsilesional(IL) and contralesional(CL) regions of interest (ROI) from supra-threshold Z-score voxels (Z-score > 2.3) on sensorimotor network (SMN) were used to evaluate BOLD signal changes on Z score maps. Asymmetry score were also calculated based on numbers of supra-thershold voxels between IL and CL in tumor patients and between I and C ROIs in control cases. Statistically significant differences between the each subgroup were tested using a two-tailed t-test. RESULTS: In patients with tumor involving SMN, overall decreased BOLD signal by supra-threshold voxel count and mean Z-score was noted in both IL and CL ROIs (mean +/- standard deviation, voxel number: IL: 2376 +/- 1366, CL: 2906 +/- 1210, mean Z-score: IL: 3.7 +/- 0.3, CL: 3.65 +/- 0.3) compared to brain tumor located outside SMN (voxel number: IL: 3258 +/- 1370, CL: 3413 +/- 1467, mean Zscore: IL: 4.0 +/- 0.4, CL: 3.9 +/- 0.4). The asymmetry score was also higher in tumor involving SMN group than those not (0.1 vs 0.02). Overall increased amplitude of BOLD signal and decreased spatial extent of network of whole SMN were depicted in patients with brain tumor as compared with normal subjects. However, these differences were not statistically significant. CONCLUSION: We have demonstrated that brain tumor might cause changes of the spatial extent and amplitude of SMN on rsfRMI without significant differences observed. Resting fMRI and connectivity analysis are task-independent, and have potential clinical utility in the presurgical evaluation of patients with brain tumors, and may help in uncooperative or pediatric patients

Background/UNASSIGNED:The corpus callosum is implicated in the pathophysiology of autism spectrum disorder (ASD). However, specific structural deficits and underlying mechanisms are yet to be well defined. Methods/UNASSIGNED:) diffusivities, which reflect myelination and microstructural organization of the extracellular space. The relationships between DKI metrics and processing speed, a cognitive feature known to be impaired in ASD, were also examined. Results/UNASSIGNED: > .05). Conclusion/UNASSIGNED:Decreased DKI metrics suggested that ASD may be associated with axonal deficits such as reduced axonal caliber and density in the corpus callosum, especially in the mid and posterior callosal areas. These data suggest that impaired interhemispheric connectivity may contribute to decreased processing speed in ASD participants.