Changes In Diffusion Values Research Articles

DTI FOR DIAGNOSING HYPOXICISCHEMIC BRAIN INJURE IN PRETERM NEONATES

The perinatal lesions of the nervous system in newborns include a number of diseases of the brain, spinal cord and peripheral nerves, united in a group by the time of exposure to damaging factors. The MRI is recognized as the most infor mative and specific method for the diagnosis of perinatal lesions of the central nervous system. By using the MRI, it is possible not only to identify structural changes in the brain, but also to qualitatively assess the myelination of cerebral structures in preterm infants. It was shown that in severe hypoxic-ischemic damage in preterm infants, dysmyelination is more often determined in the posterior pedicle of the inner capsule. DTI is a promising method to quantify the degree of myelination of the brain, visualize pathways, assess their structure and integrity. The aim of the study was to identify significant differences in diffusion values according to DTI in preterm infants with severe hypoxic-ischemic brain injures in the form of periventricular leucomalatia and peri-intraventricular hemorrhage. Methods: Group 1 (10 children) consisted of patients who did not have structural changes on MRI. Group 2 (8 children) consisted of children with periventricular leukomalacia. Group 3 (4 children) consisted of children with peri-intraventricular hemorrhages. The patients was underwent MRI, diffusion-tensor MRI. A comparison was made of the diffusion values in the posterior limb of inner capsules and the thalami between the groups. Results: there were revealed changes in diffusion values, indicating a delay of myelination at the level of the posterior legs of the inner capsules in children with severe hypoxic-ischemic brain injures.

A longitudinal study of changes in Diffusion Tensor Value and their association with cognitive sequelae among patients with mild head injury.

Diffusion tensor imaging (DTI) is an advanced and sensitive technique that detects sub-threshold pathology in normal imaging brain injury patients. Currently, there are no longitudinal DTI studies to look for time-based changes. The present study has investigated longitudinal imaging and its association with cognitive deficits. Twenty-one patients were available for MRI and neuropsychological test (NPT) assessment for all the 3 time points. Initially (<36 hours), all patients presented with GCS 15 and normal scan findings. The DTI (P<0.0001) and NPT scores (P<0.05) were analyzed using repeated-measure of analysis. The tensor values were correlated with specific time-point NPT scores using partial correlation (0.05). Right cerebral-hemisphere showed significant alterations in both anisotropy and diffusivity values overtime. Cingulate gyrus and occipital lobe showed prominent changes in anisotropy value. Significant improvement in thalamo-cortical anisotropy value after 3-4 months after injury was seen. The changes in diffusivity values were mainly seen in frontal, parietal lobe, right inferior fronto-occipital and superior longitudinal fasciculus, and posterior supramarginal gyrus. Time-related changes of tensor values of thalamus, frontal and temporal lobe had persistent and significant association with attention and learning/memory aspects. The findings of this study suggest that DTI detects and observes natural-recovery of brain regions affected by sub-threshold force.

Apparent diffusion coefficient histogram analysis of neonatal hypoxic–ischemic encephalopathy

Diffusion-weighted imaging is a valuable tool in the assessment of the neonatal brain, and changes in diffusion are seen in normal development as well as in pathological states such as hypoxic-ischemic encephalopathy (HIE). Various methods of quantitative assessment of diffusion values have been reported. Global ischemic injury occurring during the time of rapid developmental changes in brain myelination can complicate the imaging diagnosis of neonatal HIE. To compare a quantitative method of histographic analysis of brain apparent coefficient (ADC) maps to the qualitative interpretation of routine brain MR imaging studies. We correlate changes in diffusion values with gestational age in radiographically normal neonates, and we investigate the sensitivity of the method as a quantitative measure of hypoxic-ischemic encephalopathy. We reviewed all brain MRI studies from the neonatal intensive care unit (NICU) at our university medical center over a 4-year period to identify cases that were radiographically normal (23 cases) and those with diffuse, global hypoxic-ischemic encephalopathy (12 cases). We histographically displayed ADC values of a single brain slice at the level of the basal ganglia and correlated peak (s-sDav) and lowest histogram values (s-sDlowest) with gestational age. Normative s-sDav values correlated significantly with gestational age and declined linearly through the neonatal period (r (2) = 0.477, P < 0.01). Six of 12 cases of known HIE demonstrated significantly lower s-sDav and s-sDlowest ADC values than were reflected in the normative distribution; several cases of HIE fell within a 95% confidence interval for normative studies, and one case demonstrated higher-than-normal s-sDav. Single-slice histographic display of ADC values is a rapid and clinically feasible method of quantitative analysis of diffusion. In this study normative values derived from consecutive neonates without radiographic evidence of ischemic injury are correlated with gestational age, declining linearly throughout the perinatal period. This method does identify cases of HIE, though the overall sensitivity of the method is low.

Myelination deficits in schizophrenia: evidence from diffusion tensor imaging

Diffusion Tensor Imaging studies have repeatedly shown a decrease of the fractional anisotropy (FA) parameter in patients with schizophrenia. This has been interpreted as a disturbed microstructural integrity of white matter. However, FA is a relative parameter that is derived from eigenvalues of the diffusion tensor and FA reductions may be the result of decreases in parallel diffusivity (PD) or increases in radial diffusivity (RD). Despite the well-established FA reduction in schizophrenia, little is known what this reduction is based on. Seventeen patients with schizophrenia were scanned with a DTI protocol and compared to a group of healthy control subjects. In addition to an FA comparison, a detailed analysis of PD and RD values was performed with two approaches to localize changes in diffusion values, i.e. a voxel-based analysis and an anatomically based tract specific analysis. We found significantly decreased FA values in the patient group when compared to healthy controls. FA decreases were based on an increase in RD, while we observed no significant changes of PD. These changes were predominantly localized in frontal and temporal areas. RD increases as the underlying change in FA decreases is suggestive of desintegration of myelin, which is in line with histopathological studies suggesting a disturbed myelination in schizophrenia.