DTI Metrics (dti + metric)

Distribution by Scientific Domains

Selected Abstracts

Retrograde Wallerian degeneration of cranial corticospinal tracts in cervical spinal cord injury patients using diffusion tensor imaging

Saurabh Guleria
Abstract Diffusion tensor imaging (DTI) has the potential to reveal disruption of white matter microstructure in chronically injured spinal cords. We quantified fractional anisotropy (FA) and mean diffusivity (MD) to demonstrate retrograde Wallerian degeneration (WD) of cranial corticospinal tract (CST) in cervical spinal cord injury (SCI). Twenty-two patients with complete cervical SCI in the chronic stage were studied with DTI along with 13 healthy controls. Mean FA and MD values were computed for midbrain, pons, medulla, posterior limb of internal capsule, and corona radiata. Significant reduction in the mean FA and increase in MD was observed in the cranial CST in patients with SCI compared with controls, suggesting retrograde WD. Statistically significant inverse FA and MD changes were noted in corona radiata, indicating some restoration of spared white matter tracts. Temporal changes in the DTI metrics suggest progressing degeneration in different regions of CST. These spatiotemporal changes in DTI metrics suggest continued WD in injured fibers along with simultaneous reorganization of spared white matter fibers, which may contribute to changing neurological status in chronic SCI patients. 2008 Wiley-Liss, Inc. [source]

Diffusion tensor MRI in rat models of invasive and well-demarcated brain tumors

Sungheon Kim
Abstract Diffusion tensor imaging (DTI) and its metrics, such as mean diffusivity (MD) and fractional anisotropy (FA), have been used to detect the extent of brain tumors and understand tumor growth and its influence on the surrounding tissue. However, there are conflicting reports on how DTI metrics can be used for tumor diagnosis. The physiological interpretation of these metrics in terms of tumor growth is also not clear. The objective of this study was to investigate the DTI parameters in two rat brain tumor models (9L and F98) with different patterns of aggressiveness by longitudinal monitoring of tumor growth and comparing the DTI parameters of these two tumor models. In addition to the standard DTI metrics, MD and FA, we measured other metrics representing diffusion tensor shape, such as linear and planar anisotropy coefficients (CL and CP), and orientational coherence measured by lattice index (LI), to characterize the two tumor models. The 9L tumor had higher FA, CL, and LI than the F98 tumor. F98 had a larger difference in anisotropies between tumor and peritumor regions than 9L. From the eigenvalues, it was found that the increase in CL and trace of the 9L tumor was due to an increase in the primary eigenvalue, whereas the increase in CP in the peritumor region was due to an increase in both primary and secondary eigenvalues and a decrease in tertiary eigenvalue. Our results indicate that shape-oriented anisotropy measures, such as CL and CP, and orientational coherence measures, such as LI, can provide useful information in differentiating these two tumor models and also differentiating tumor from peritumoral regions. Copyright 2007 John Wiley & Sons, Ltd. [source]

Progressive brain changes in schizophrenia: a 1-year follow-up study of diffusion tensor imaging

Miho Ota
Objective: Recent cross-sectional studies suggest that brain changes in schizophrenia are progressive during the course of the disorder. However, it remains unknown whether this is a global process or whether some brain areas are affected to a greater degree. The aim of this study was to examine the longitudinal brain changes in patients with chronic older schizophrenia by magnetic resonance imaging (MRI). Methods: Three-dimensional (3D) T1-weighted and diffusion tensor (DT) MRI were performed twice on each of 16 chronic older schizophrenia patients (mean age = 58.1 6.7 years ) with an interval of 1 year between imaging sessions. To clarify the longitudinal morphological and white matter changes, volume data and normalised diffusion tensor imaging (DTI) metrics were compared between the first and follow-up studies using a paired t -test. Results: Focal cortical volume loss was observed in the left prefrontal lobe and anterior cingulate on volumetric study. In addition, DTI metrics changed significantly at the bilateral posterior superior temporal lobes, left insula, genu of the corpus callosum and anterior cingulate. Conclusion: There are ongoing changes in the brains of schizophrenic patients during the course of the illness. Discrepancies between volume data and DTI metrics may indicate that the pattern of progressive brain changes varies according to brain region. [source]