The ellipsoidal area ratio: an alternative anisotropy index for diffusion tensor imaging
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Background: Diffusion Weighted Imaging and Diffusion Tensor Imaging is an advanced technique in MRI that shows the diffusion in brain of ischemic stroke disease. Diffusion Weighted Imaging (DWI) shows the lesions without gadolinium contrast agent and produce Apparent Diffusion Coefficient values. Whereas, Diffusion Tensor Imaging (DTI) shows connectivity’s of central nervous system that cannot be seen by using conventional MRI. Diffusion Tensor Imaging produces Fractional Anisotropy values. Purpose:This study has aim to analyze the Apparent Diffusion Coefficient values and Fractional Anisotropy values in Stroke Ischemic disease. Methods: Total samples used are 14 samples, consist of 7 (50%) man and 7 (50%) woman with ischemic stroke disease. Each sample deals by Diffusion Weighted Imaging and Diffusion Tensor Imaging sequences. The Region of Interest (ROI) is placed in ischemic stroke lesions and contra lateral side of lesions. Results: The result shows that 9 samples of brain tissue lesions located in the right side and 5 samples in the left side. Right lesions have the average ADC stroke: 0.001748; normal ADC: 0.000954; FA stroke: 0.144522; and normal FA: 0.426111. While, left lesions have the average ADC strokes 0.000979; normal ADC: 0.000835; FA stroke: 0.2556; and normal FA 0.4324. Conclusion: So, the conclusion of this study is Apparent Diffusion Coefficient (ADC) values in case of ischemic stroke can decreases or increases depend on the age of stroke. While, the Fractional Anisotropy (FA) values will decrease without being affected by age of stroke.
Stroke
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Diffusion tensor imaging is currently the best noninvasive technique to assess microstructural changes in white matter pathways, which enables quantitative assessment of brain normal structures, brain development and lesions by calculating the apparent diffusion coefficient, fractional anisotropy, relative anisotropy and parallel diffusivity, etc. In order to improve the study on neonatal brain injuries, the application of diffusion tensor imaging in neonatal fields was reviewed in this paper.
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Diffusion tensor imaging; Brain development; White matter; Brain injury; Newborn infant
Diffusion imaging
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This study meta-analyzed research examining Diffusion Tensor Imaging following pediatric non-penetrating traumatic brain injury to identify the location and extent of white matter changes. Fractional anisotropy (FA) and apparent diffusion coefficient (ADC) data from 20 studies were analyzed. FA increased and ADC decreased in most white matter tracts in the short-term (moderate-to-large effects), and FA decreased and ADC increased in the medium- to long-term (moderate-to-very-large effects). Whole brain (short-term), cerebellum and corpus callosum (medium- to long-term) FA values have diagnostic potential, but the impact of age/developmental stage and injury severity on FA/ADC, and the predictive value, is unclear.
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Epileptic seizure in pediatric patients affects neurodevelopment, and surgical treatment of intractable epilepsy improved comorbidities, but the mechanism is not fully uncovered yet. By measurement of MRI-DTI Fractional Anisotropy (FA) of posterior limb of internal capsule (PIC) of infants, we presented its change by seizure propagation and control in a case of an infant post traumatic epilepsy (PTE) caused by growing skull fracture. Her motor developmental delay and hemiparesis with non-convulsive status epilepticus (NCSE) started 2 months after injury, recovered after surgical repair and seizure control. FA of PIC was lower than normal (0.29 ipsilateral, 0.37 contralateral) had increased to normal range in one week after surgical treatment and seizure control (0.62, 0.66). Comparing with normal time course of FA of motor tract of infant, this dynamic change of FA indicated the effect of seizure control after surgical treatment. As measurement of other brain lesion also showed increased FA in both ipsilateral and contralateral deep white matter, indicated the effect of NCSE for wide network of brain, and influenced infant neuronal development. These result indicated one mechanism why NCSE affected motor developmental delay and surgical intervention for regional infant intractable epilepsy prevented further developmental delay. By handy method of measuring FA of motor tract, we had one possibility to predict motor tract injury in infancy. We also reviewed and discussed about the mechanism of FA increase and decrease in early infancy and how PTE caused FA change.
Omics
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The aim is to investigate the relationship between microstructural white matter (WM) diffusivity indices and macrostructural WM volume (WMV) among healthy individuals (20-85 years). Whole-brain diffusion measures were calculated from diffusion tensor imaging using FMRIB software library while WMV was estimated through voxel-based morphometry, and voxel-based analysis was carried out using tract-based spatial statistics. Our results revealed that mean diffusivity, axial diffusivity, and radial diffusivity had shown good correlation with WMV but not for fractional anisotropy (FA). Voxel-wise tract-based spatial statistics analysis for FA showed a significant decrease in four regions for middle-aged group compared to young-aged group, in 22 regions for old-aged group compared to middle-aged group, and in 26 regions for old-aged group compared to young-aged group (P < 0.05). We found significantly lower WMV, FA, and mean diffusivity values in females than males and inverted-U trend for FA in males. We conclude differential age- and gender-related changes for structural WMV and WM diffusion indices.
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The fractional anisotropy value of the brain white matter region was analyzed by Tract-Based Spatial Statics(TBSS) method after acquiring the diffusion tensor image to identify the presence or absence of brain white matter damage to smoking in male. As a result, smokers showed lower fractional anisotropy than non-smokers in all areas but fractional anisotropy values were not statistically significant. the fractional anisotropy value, on the other hand, was statistically significant only for the right choroid plexus. In other words smoking, although, does not significantly affect the micro structural changes of brain white matter, it affects the choroid plexus area.
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To determine whether diffusion tensor imaging (DTI) can detect diffuse axonal injury, and to evaluate the association of DTI findings with motor function in patients with traumatic brain injury.Three case studies.An inpatient rehabilitation unit in Korea.Three patients with traumatic brain injury in whom conventional neuroimaging showed normal-appearing white matter.Patients were studied with DTI. Fractional anisotropy (FA) was measured from 3 different anatomic locations on both sides of the corticospinal tract. Motor function was evaluated using the motoricity index.Fractional anisotropy tended to be reduced in normal-appearing corticospinal tracts that were remote from the involved segment. Diffusion tensor imaging showed reduction of FA in areas consistent with motor dysfunction.Fractional anisotropy of the corticospinal tract may be used in the detection of diffuse axonal injury. The association between decreased motoricity index and decreased FA suggests that DTI may be useful in evaluating patients with traumatic brain injury.
Corticospinal tract
Diffuse axonal injury
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Objective : To assess the perioperative fractional anisotropy (FA) /apparent diffusion coefficient (ADC) change in patients with cerebrospinal disease using highly accurate diffusion tensor imaging (Zoom DTI), and to determine the prognostic value.
Neurologic disease
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Abstract In diffusion tensor imaging, structural connectivity between brain regions is often measured by the number of white matter fiber tracts connecting them. Other features such as the length of tracts or fractional anisotropy (FA) are also used in measuring the strength of connectivity. In this study, we investigated the effects of incorporating the number of tracts, the tract length and FA-values into the connectivity model. Using various node-degree based graph theory features, the three connectivity models are compared. The methods are applied in characterizing structural networks between normal controls and maltreated children, who experienced maltreatment while living in post-institutional settings before being adopted by families in the US.
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This paper investigates whether diffusion tensor imaging performed within 2 weeks of intracerebral hemorrhage onset could predict the motor outcome by categorizing previous diffusion tensor imaging studies based on the time-point of performing diffusion tensor imaging (<2 weeks and ≥2 weeks after intracerebral hemorrhage onset). A comprehensive database search on PubMed, Embase, Cochrane Library, and SCOPUS was conducted. The pooled estimate was acquired using correlation analysis between the diffusion tensor imaging parameters of fractional anisotropy and motor recovery based on the period of stroke onset. In the results, out of 511 retrieved articles, eight were finally included in the meta-analysis. In patients who underwent diffusion tensor imaging within 2 weeks of intracerebral hemorrhage onset, a random-effects model revealed that the ratio of fractional anisotropy is a significant predictor of motor recovery of the hemi-side extremity after intracerebral hemorrhage (p = 0.0015). In patients who underwent diffusion tensor imaging after 2 weeks of intracerebral hemorrhage onset, a fixed-effects model revealed that the ratio of fractional anisotropy was also a significant predictor of motor recovery of the hemi-side extremity after intracerebral hemorrhage (p < 0.0001). Our meta-analysis revealed that ratio of fractional anisotropy (rFa) calculated from diffusion tensor imaging (DTI) performed ≥2 weeks of intracerebral hemorrhage onset had a positive correlation with the motor outcomes after intracerebral hemorrhage (ICH). Also, although diffusion tensor imaging was performed <2 weeks after intracerebral hemorrhage onset, the ratio of fractional anisotropy calculated from diffusion tensor imaging helped predict the motor outcome. Further analyses, including a more significant number of studies focused on this topic, are warranted.
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