Synthetic Apparent Diffusion Coefficient for High b-Value Diffusion-Weighted MRI in Prostate.

PURPOSE: It has been reported that diffusion-weighted imaging (DWI) with ultrahigh b-value increases the diagnostic power of prostate cancer. DWI with higher b-value increases the diagnostic power of prostate cancer. DWI with higher b-value increases the diagnostic power of prostate cancer. DWI with higher b-value increases the diagnostic power of prostate cancer. DWI with higher Materials and Methods. Fifteen patients (7 malignant and 8 benign) were included in this study retrospectively with the institutional ethical committee approval. All images were acquired at a 3T MR scanner. The ADC values were calculated using a monoexponential model. Synthetic ADC (sADC) for higher b-value increases the diagnostic power of prostate cancer. DWI with higher. RESULTS: No significant difference was observed between actual ADC and sADC for b-value increases the diagnostic power of prostate cancer. DWI with higher p=0.002, paired t-test) in sDWI as compared to DWI. Malignant lesions showed significantly lower sADC as compared to benign lesions (p=0.002, paired t-test) in sDWI as compared to DWI. Malignant lesions showed significantly lower sADC as compared to benign lesions (Discussion/. CONCLUSION: Our initial investigation suggests that the ADC values corresponding to higher b-value can be computed using log-linear relationship derived from lower b-values (b ≤ 1000). Our method might help clinicians to decide the optimal b-value for prostate lesion identification.b-value increases the diagnostic power of prostate cancer. DWI with higher b-value increases the diagnostic power of prostate cancer. DWI with higher b-value increases the diagnostic power of prostate cancer. DWI with higher b-value increases the diagnostic power of prostate cancer. DWI with higher.

Comparative evaluation of 3-dimensional pseudocontinuous arterial spin labeling with dynamic contrast-enhanced perfusion magnetic resonance imaging in grading of human glioma.

INTRODUCTION: The study was performed to compare dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) with 3-dimensional (3D) pseudocontinuous arterial spin labeling (PCASL) MRI in gliomas with an aim to see whether arterial spin labeling (ASL)-derived cerebral blood flow (CBF) values can be used as an alternative to DCE-MRI for its grading. MATERIALS AND METHODS: Sixty-four patients with glioma (37 male; mean age, 43 years; 38 high grade and 26 low grade) underwent 3D-PCASL and DCE-MRI. The DCE indices (relative cerebral blood volume, rCBV; relative CBF, rCBF; permeability, k and kep; and leakage, ve) and ASL (absolute and rCBF) values were quantified from the tumors. Student independent t test was used to compare ASL and DCE-MRI indices. Pearson correlation was used to see correlation between DCE- and ASL-derived CBF values in tumor and normal parenchyma. RESULTS: On Student t test, neither ASL-derived absolute CBF (P = 0.78) nor rCBF (P = 0.12) values were found to be significantly different in 2 groups, whereas DCE indices except ve were significantly higher in high-grade gliomas. Arterial spin labeling-derived rCBF values weakly correlated with DCE-derived rCBF values, whereas these did not show correlation in normal grey (P = 0.12, r = 0.2) and white (P = 0.26, r = 0.14) matter regions. CONCLUSIONS: Three-dimensional pseudocontinuous arterial spin labeling does not appear to be a reliable technique in the current form and may not be a suitable replacement for DCE in grading of glioma.

Subcompartmentalization of extracellular extravascular space (EES) into permeability and leaky space with local arterial input function (AIF) results in improved discrimination between high- and low-grade glioma using dynamic contrast-enhanced (DCE) MRI.

PURPOSE: To modify the generalized tracer kinetic model (GTKM) by introducing an additional tissue uptake leakage compartment in extracellular extravascular space (LTKM). In addition, an implicit determination of voxel-wise local arterial input function (AIF) Cp (t) was performed to see whether these changes help in better discrimination between low- and high-grade glioma using dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI). MATERIALS AND METHODS: The modified model (LTKM) was explored and fitted to the concentration-time curve C(t) of each voxel, in which the local AIF Cp (t) could be estimated by a time invariant convolution approximation based on a separately measured global AIF Ca (t). A comparative study of tracer kinetic analysis was performed on 184 glioma patients using DCE-MRI data on 1.5T and 3T MRI systems. RESULTS: The LTKM analysis provided more accurate pharmacokinetic parameters as evidenced by their relative constancy with respect to the length of concentration-time curve used. In addition, LTKM with local AIF resulted in improved discrimination between low-grade and high-grade gliomas. CONCLUSION: LTKM with local AIF provides more accurate estimation of physiological parameters and improves discrimination between low-grade and high-grade gliomas as compared with GTKM.

Utility of multiparametric 3-T MRI for glioma characterization.

INTRODUCTION: Accurate grading of cerebral glioma using conventional structural imaging techniques remains challenging due to the relatively poor sensitivity and specificity of these methods. The purpose of this study was to evaluate the relative sensitivity and specificity of structural magnetic resonance imaging and MR measurements of perfusion, diffusion, and whole-brain spectroscopic parameters for glioma grading. METHODS: Fifty-six patients with radiologically suspected untreated glioma were studied with T1- and T2-weighted MR imaging, dynamic contrast-enhanced MR imaging, diffusion tensor imaging, and volumetric whole-brain MR spectroscopic imaging. Receiver-operating characteristic analysis was performed using the relative cerebral blood volume (rCBV), apparent diffusion coefficient, fractional anisotropy, and multiple spectroscopic parameters to determine optimum thresholds for tumor grading and to obtain the sensitivity, specificity, and positive and negative predictive values for identifying high-grade gliomas. Logistic regression was performed to analyze all the parameters together. RESULTS: The rCBV individually classified glioma as low and high grade with a sensitivity and specificity of 100 and 88 %, respectively, based on a threshold value of 3.34. On combining all parameters under consideration, the classification was achieved with 2 % error and sensitivity and specificity of 100 and 96 %, respectively. CONCLUSION: Individually, CBV measurement provides the greatest diagnostic performance for predicting glioma grade; however, the most accurate classification can be achieved by combining all of the imaging parameters.

Individual differences in trait anxiety are associated with white matter tract integrity in fornix and uncinate fasciculus: preliminary evidence from a DTI based tractography study.

Trait anxiety, a personality dimension that measures an individual's higher disposition to anxiety, has been found to be associated with many functional consequences viz. increased distractibility, attentional bias in favor of threat-related information etc. Similarly, volumetric studies have reported morphological changes viz. a decrease in the volume of left uncinate fasciculus (fiber connecting anterior temporal areas including the amygdala with prefrontal-/orbitofrontal cortices) and an increase in the volume of the left amygdala and right hippocampus, to be associated with trait anxiety. The functional and morphological changes associated with trait anxiety might also be associated with the changes in the integrity of WM tracts in relation with the trait anxiety levels of the subjects. Therefore, in the present diffusion tensor tractography (DTT) study, we investigated the possible relationship between the diffusion tensor imaging (DTI) derived indices of a wide array of fiber tracts and the trait anxiety scores in our subject group. A positive correlation between trait anxiety scores and the mean fractional anisotropy (FA) value was obtained in fornix and left uncinate fasciculus. The study provides first account of a positive relation between sub-clinical anxiety levels of subjects and the FA of fornix thereby providing interesting insights into the biological foundation of sub-clinical anxiety.

Serial evaluation of children with ALF with advanced MRI, serum proinflammatory cytokines, thiamine, and cognition assessment.

OBJECTIVES: This prospective, sequential study was done to understand changes in cerebral edema (CE) on magnetic resonance imaging and magnetic resonance spectroscopy, liver functions, and neurocognitive testing (NCT) in children with acute liver failure (ALF). METHODS: A total of 11 ALF and 8 healthy controls were evaluated with advanced magnetic resonance (MR) imaging, blood proinflammatory cytokines (PCs), thiamine levels, liver functions, and NCT. Reevaluation was done at 43.5 ±â€Š26.9 days (first follow-up, n = 8) and 157.3 ±â€Š52.3 days (second follow-up, n = 6) after discharge. RESULTS: At diagnosis, patients with ALF had vasogenic and cytotoxic CE, raised brain glutamine (23.2 ±â€Š3.4 vs. 15.3 ±â€Š2.7), and serum PCs (tumor necrosis factor [TNF]-α 40.1 ±â€Š8.9 vs. 7.2 ±â€Š2.7  pg/mL, interleukin [IL]-6 29.2 ±â€Š14.4 vs. 4.7 ±â€Š1.2  pg/mL). The mammillary bodies (MBs) were smaller, and brain choline (1.9 ±â€Š0.36 vs. 2.6 ±â€Š0.6) and blood thiamine (55.2 ±â€Š6.7 vs. 81.8 ±â€Š10.2  nmol/L) were lower than controls. At first follow-up, the brain glutamine and CE recovered. Brain choline and MBs volume showed improvement and thiamine levels normalized. Significant reduction in TNF-α and IL-6 was seen. The patients performed poorly on NCT, which normalized at second follow-up. Liver biochemistry and thiamine levels were normal and TNF-α and IL-6 showed further reduction at second follow-up. CONCLUSIONS: Patients with ALF have CE contributed by raised brain glutamine and PCs. MBs are small because of thiamine deficiency and show recovery in follow-up. CE and brain glutamine recover earlier than normalization of NCT and liver functions. Persistence of raised cytokines up to 6 months after insult suggests possible contribution from liver regeneration.

Radiation-induced early changes in the brain and behavior: serial diffusion tensor imaging and behavioral evaluation after graded doses of radiation.

The nuclear arsenal and the use of nuclear technologies have enhanced the likelihood of whole-body/partial-body radiation exposure. The central nervous system is highly susceptible to even low doses of radiation. With the aim of detecting and monitoring the pathologic changes of radiation-induced damage in brain parenchyma, we used serial diffusion tensor magnetic resonance imaging (DTI) with a 7T magnetic resonance unit and neurobehavioral assessments mice irradiated with 3-, 5-, and 8-Gy doses of radiation. Fractional anisotropy (FA) and mean diffusivity (MD) values at each time point (baseline, day 1, day 5, and day 10) were quantified from hippocampus, thalamus, hypothalamus, cudate-putamen, frontal cortex, sensorimotor cortex, corpus callosum, cingulum, and cerebral peduncle. Behavioral tests were performed at baseline, day 5, and day 10. A decrease in FA values with time was observed in all three groups. At day 10, dose-dependent decreases in FA and MD values were observed in all of the regions compared with baseline. Behavioral data obtained in this study correlate with FA values. Radiation-induced affective disorders were not radiation dose dependent, insofar as the anxiety-like symptoms at the lower dose (3 Gy) mimics to the symptoms with the higher dose (8 Gy) level but not with the moderate dose. However, there was a dose-dependent decline in cognitive function as well as FA values. Behavioral data support the DTI indices, so it is suggested that DTI may be a useful tool for noninvasive monitoring of radiation-induced brain injury.

Dynamic contrast-enhanced magnetic resonance imaging-derived kep as a potential biomarker of matrix metalloproteinase 9 expression in patients with glioblastoma multiforme: a pilot study.

OBJECTIVE: To look for the association of tissue matrix metalloproteinase 9 (MMP-9) expression with dynamic contrast-enhanced magnetic resonance imaging and to see whether these can prognosticate patients with glioblastoma multiforme (GBM). METHODS: Forty-seven patients with GBM underwent dynamic contrast-enhanced magnetic resonance imaging to look for association of its indices with tissue MMP-9 expression using Pearson correlation. Kaplan-Meier survival analysis was performed to study the survival pattern for low-, medium-, and high-tissue MMP-9 expression and kep values. RESULTS: Among perfusion indices, kep, k, and ve significantly correlated with MMP-9 expression. Matrix metalloproteinase 9 expression was found to be best estimated by kep using a quadratic model. The 1-year survival in low-, medium-, and high-tissue MMP-9 and kep groups were 59%, 45%, and 7%, and 59%, 33%, and 15%, respectively. CONCLUSION: The association of kep and MMP-9 expression with survival suggests that kep may be used as imaging biomarker of GBM progression and its prognostication.

Diffusion tensor tractography indices in patients with frontal lobe injury and its correlation with neuropsychological tests.

OBJECTIVES: Diffusion tensor tractography (DTT) was performed to quantify diffuse axonal injury (DAI) in major white matter (WM) fiber bundles (FBs) of patients with frontal lobe injury and to correlate these changes with neuropsychological tests (NPT) at 6 month follow-up. PATIENTS AND METHODS: DTT was performed in 21 patients with moderate traumatic brain injury (TBI) within week and after 6 month follow-up, and in controls. DTI indices were calculated from the entire FBs in patients as well as controls. Bonferroni multiple comparisons Post hoc test was performed for determining the changes in DTI indices. Paired t-test was performed between DTI indices at baseline and follow-up. Pearson's correlation was performed between NPT scores and DTI indices. RESULTS: Significant changes in DTI indices were observed in some of the FBs as compared to controls which incompletely recovered at 6 month follow-up. DTI indices of different WM FBs correlated significantly with some of the NPT. CONCLUSION: We conclude that DTT based quantification helps in assessment of DAI in patients with moderate frontal lobe injury. Some of the FBs recover partially at 6 month follow-up and correlate with NPT scores.

Discriminant analysis to classify glioma grading using dynamic contrast-enhanced MRI and immunohistochemical markers.

INTRODUCTION: The purpose of the present study was to look for the possible predictors which might discriminate between high- and low-grade gliomas by pooling dynamic contrast-enhanced (DCE)-perfusion derived indices and immunohistochemical markers. METHODS: DCE-MRI was performed in 76 patients with different grades of gliomas. Perfusion indices, i.e., relative cerebral blood volume (rCBV), relative cerebral blood flow (rCBF), permeability (k (trans) and k (ep)), and leakage (v (e)) were quantified. MMP-9-, PRL-3-, HIF-1α-, and VEGF-expressing cells were quantified from the excised tumor tissues. Discriminant function analysis using these markers was used to identify discriminatory variables using a stepwise procedure. To look for correlations between immunohistochemical parameters and DCE metrics, Pearson's correlation coefficient was also used. RESULTS: A discriminant function for differentiating between high- and low-grade tumors was constructed using DCE-MRI-derived rCBV, k (ep), and v (e). The form of the functions estimated are "D (1) = 0.642 × rCBV + 0.591 × k (ep) - 1.501 × v (e) - 1.550" and "D (2) = 1.608 × rCBV + 3.033 × k (ep) + 5.508 × v (e) - 8.784" for low- and high-grade tumors, respectively. This function classified overall 92.1% of the cases correctly (89.1% high-grade tumors and 100% low-grade tumors). In addition, VEGF expression correlated with rCBV and rCBF, whereas MMP-9 expression correlated with k (ep). A significant positive correlation of HIF-1α with rCBV and VEGF expression was also found. CONCLUSION: DCE-MRI may be used to differentiate between high-grade and low-grade brain tumors non-invasively, which may be helpful in appropriate treatment planning and management of these patients. The correlation of its indices with immunohistochemical markers suggests that this imaging technique is useful in tissue characterization of gliomas.

Understanding changes in DTI metrics in patients with different stages of neurocysticercosis.

Diffusion tensor imaging (DTI) was performed on 25 patients with neurocysticercosis (NCC). The aim of this study was to investigate the changes in DTI measures during the evolutionary course of NCC lesions from vesicular to calcified stage in the brain. DTI measures were quantified from the NCC lesions of all patients. On the basis of conventional imaging findings, NCC lesions were classified into vesicular, vesicular colloidal, granular nodular and calcified stages. Significant inverse correlation was observed between the evolutionary stage of NCC lesion and mean diffusivity (MD; r=-0.748, P<0.001) and spherical anisotropy (CS; r=-0.585, P<.001) values. Significant direct correlations were observed between evolutionary stages of NCC lesion and mean fractional anisotropy (FA; r=0.575, P<0.001), linear anisotropy (CL; r=0.478, p<0.001) and planar anisotropy (CP; r=0.561, p<0.001) values. Successive decrease in MD values calculated from NCC lesions was observed, moving from vesicular to granular nodular stage. On FA, CL and CP maps, a significant increase in signal intensity value was observed in calcified as compared to other stages. We conclude that DTI measures may indicate the evolutionary changes in NCC from vesicular to calcified stage.

Correlation of diffusion tensor imaging metrics with neurocognitive function in Chiari I malformation.

BACKGROUND: The aim of this study was to examine changes in normal-appearing deep gray and white matter regions of the brain in patients with Chiari I malformation compared with controls using diffusion tensor imaging (DTI) and to correlate these changes with neuropsychological (NP) test scores. METHODS: Conventional magnetic resonance imaging, DTI, and neuropsychological tests were performed on 10 patients (median age 27 years, range 18 to 36 years) with Chiari I malformation and 10 age/sex-matched healthy controls. Diffusion tensor imaging metrics (fractional anisotropy, mean diffusivity [MD], radial diffusivity [RD], and axial diffusivity [AD]) were quantified in different regions of the brain in patients as well as in controls using the region of interest (ROI) method. An independent Student t test was performed to evaluate differences in diffusion tensor imaging metrics from patients and controls. Pearson's correlation coefficient was also used to determine association between NP test scores and DTI metrics in patients. RESULTS: Significantly reduced fractional anisotropy with increased MD was found in genu, splenium, fornix, and putamen in patients compared with controls; however, RD significantly increased in fornix and cingulum, whereas AD significantly increased in putamen, thalamus, and fornix as compared with controls. NP tests were found to be abnormal in patients with Chiari I malformation compared with controls, and some of these tests showed significant correlation with DTI metrics. CONCLUSIONS: We conclude that abnormal changes in the DTI metrics in patients with Chiari I malformation indicate microstructural abnormalities in different brain regions that may be associated with neurocognitive abnormalities.

Principal eigenvector field segmentation for reproducible diffusion tensor tractography of white matter structures.

The study was aimed to test the feasibility of utilizing an algorithmically determinable stable fiber mass (SFM) map obtained by an unsupervised principal eigenvector field segmentation (PEVFS) for automatic delineation of 18 white matter (WM) tracts: (1) corpus callosum (CC), (2) tapetum (TP), (3) inferior longitudinal fasciculus (ILF), (4) uncinate fasciculus (UNC), (5) inferior fronto-occipital fasciculus (IFO), (6) optic pathways (OP), (7) superior longitudinal fasciculus (SLF), (8) arcuate fasciculus (AF), (9) fornix (FX), (10) cingulum (CG), (11) anterior thalamic radiation (ATR), (12) superior thalamic radiation (STR), (13) posterior thalamic radiation (PTR), (14) corticospinal/corticopontine tract (CST/CPT), (15) medial lemniscus (ML), (16) superior cerebellar peduncle (SCP), (17) middle cerebellar peduncle (MCP) and (18) inferior cerebellar peduncle (ICP). Diffusion tensor imaging (DTI)-derived fractional anisotropy (FA) and the principal eigenvector field have been used to create the SFM consisting of a collection of linear voxel structures which are grouped together by color-coding them into seven natural classes to provide PEVFS signature segments which greatly facilitate the selection of regions of interest (ROIs) for fiber tractography using just a single mouse click, as compared with a manual drawing of ROIs in the classical approach. All the 18 fiber bundles have been successfully reconstructed, in all the subjects, using the single ROIs provided by the SFM approach, with their reproducibility characterized by the fact that the ROI selection is user independent. The essentially automatic PEVFS method is robust, efficient and compares favorably with the classical ROI methods for diffusion tensor tractography (DTT).

Cognitive functions correlate with diffusion tensor imaging metrics in patients with spina bifida cystica.

PURPOSE: Spina bifida cystica (SBC) is a group of neurodevelopmental defects caused by improper neural tube closure, which may be responsible for deficits in cognitive functions. The purpose of this study was to examine changes in normal appearing deep gray and white matter brain regions in SBC patients compared with controls through diffusion tensor imaging (DTI) and correlate these changes with neuropsychometric tests. METHODS: Conventional magnetic resonance imaging and neuropsychometric tests were performed on 13 patients and ten controls. DTI-derived fractional anisotropy (FA) and mean diffusivity (MD) were quantified in different brain regions in controls and patients. RESULTS: Significantly decreased FA was observed in caudate nuclei, putamen, genu, splenium, and increased FA was found in middle cerebellar peduncle (MCP) in patients compared with controls. We observed significantly increased MD in genu and splenium. However, increased MD was found in fornix of patients compared with controls. Majority of neuropsychological tests were found to be significantly impaired and some of these showed significant correlation with DTI metrics in genu, splenium, and MCP in these patients. CONCLUSIONS: We conclude that DTI metrics are significantly abnormal in deep gray matter nuclei, genu, splenium, and MCP in SBC patients and may provide microstructural basis for neuropsychological abnormalities in these patients.

Correlation of quantitative sensorimotor tractography with clinical grade of cerebral palsy.

INTRODUCTION: The purpose of this study was to determine whether tract-specific diffusion tensor imaging measures in somatosensory and motor pathways correlate with clinical grades as defined using the Gross Motor Function Classification System (GMFCS) in cerebral palsy (CP) children. METHODS: Quantitative diffusion tensor tractography was performed on 39 patients with spastic quadriparesis (mean age = 8 years) and 14 age/sex-matched controls. All patients were graded on the basis of GMFCS scale into grade II (n = 12), grade IV (n = 22), and grade V (n = 5) CP and quantitative analysis reconstruction of somatosensory and motor tracts performed. RESULTS: Significant inverse correlation between clinical grade and fractional anisotropy (FA) was observed in both right and left motor and sensory tracts. A significant direct correlation of mean diffusivity values from both motor and sensory tracts was also observed with clinical grades. Successive decrease in FA values was observed in all tracts except for left motor tracts moving from age/sex-matched controls to grade V through grades II and IV. CONCLUSION: We conclude that white matter tracts from both the somatosensory and the motor cortex play an important role in the pathophysiology of motor disability in patients with CP.

A diffusion tensor imaging study of deep gray and white matter brain maturation differences between patients with spina bifida cystica and healthy controls.

The aim of this study was to use diffusion tensor imaging (DTI) to identify differences in the maturation of deep gray matter (GM) and white matter (WM) between patients with spina bifida cystica (SBC) (n=29) with normal-appearing brains on conventional MRI, and age-matched and sex-matched healthy control participants (n=33). Changes in DTI metrics were calculated using a log-linear regression model. We observed increasing fractional anisotropy (FA) with age in the occipital, fornix, cingulum and middle cerebellar peduncles and decreasing FA with age in the genu and splenium of the corpus callosum (CC) and caudate nuclei in patients compared to controls. Increasing FA values in some of the WM structures probably represent faulty WM maturation, whereas decreasing FA values in the CC represents changes secondary to the affected WM fibers contributing to the CC. DTI changes in deep GM and WM in the absence of any abnormality on conventional MRI might provide the basis for cognitive decline in these patients.

Comparative evaluation of dynamic contrast-enhanced perfusion with diffusion tensor imaging metrics in assessment of corticospinal tract infiltration in malignant glioma.

OBJECTIVE: To compare dynamic contrast-enhanced magnetic resonance imaging (DCE MRI) with diffusion tensor imaging (DTI) for predicting tumor infiltration in a conventional MRI normal-appearing internal capsule adjacent to the tumor in patients with glioblastoma multiforme. METHODS: Thirty patients with glioblastoma multiforme underwent a neurological examination for motor assessment, DCE MRI, and DTI. On fused DCE and DTI images, regions of interest were placed on the normal-appearing internal capsule and the corresponding region of the contralateral internal capsule. These patients were pooled into group 1 (improved after surgery, n = 9) and group 2 (did not improve after surgery, n = 21) on the basis of motor strength. The DTI and perfusion metrics were statistically analyzed to look for a predictor of motor functionality. RESULTS: Multivariate logistic regression analysis showed only cerebral blood volume to be the predictor of improvement in motor functionality after surgery (P = 0.043). CONCLUSIONS: We conclude that cerebral blood volume appears to be the predictor of motor functionality after surgery and may indirectly suggest tumor infiltration, whereas DTI helps to precisely localize the fiber tracts.

Serial changes in diffusion tensor imaging metrics of corpus callosum in moderate traumatic brain injury patients and their correlation with neuropsychometric tests: a 2-year follow-up study.

OBJECTIVE: To assess longitudinally the severity of diffuse axonal injury in the corpus callosum in patients with moderate traumatic brain injury (TBI) through quantitative diffusion tensor imaging and to correlate these changes with neuropsychometric tests (NPT) at 6 and 24 months after injury. DESIGN: Prospective longitudinal study. PARTICIPANTS: Sixteen patients with TBI and 17 age/sex-matched healthy controls. METHODS: Patients underwent magnetic resonance imaging at 3 time points: within 2 weeks (range = 5-14 days), 6 months, and 24 months after injury. NPT could be performed only at 6 and 24 months. RESULTS: In patients with TBI, a significant increase in fractional anisotropy (FA) values in genu as well as an insignificant decrease in radial diffusivity (RD) and mean diffusivity values in genu and splenium were observed over time, respectively. FA, RD, and mean diffusivity values continued to be abnormal in patients compared with controls at the end of 2 years. Although some NPT scores improved over time in these patients, these were still significantly impaired compared with controls. CONCLUSIONS: FA and RD indices appear to be surrogate markers of microstructural alterations in patients over time and correlate significantly with some of the NPT scores. The recovery in these indices associated with recovery in neurocognitive deficits suggests that these indices may be used as an objective marker for residual injury in these patients.

Correlation of DTI metrics in the wall and cavity of brain abscess with histology and immunohistochemistry.

Diffusion tensor imaging (DTI) was performed in eight patients with brain abscess (BA). The aim of this study was to see the difference in the relationship between intercellular cell adhesion molecule-1 (ICAM-1) and lymphocyte function-associated antigen-1 (LFA-1) expression and DTI metrics measured in vivo in the wall and cavity of BA and its possible explanation vis-à-vis histology and immunohistochemistry. Neuroinflammatory molecules (NMs) were quantified from BA cavity aspirate of the patients and quantitative immunohistochemical analysis was performed for ICAM-1 and LFA-1 in the BA wall, showing maximal positive staining and correlated with DTI metrics. The fractional anisotropy (FA) significantly increased while mean diffusivity and spherical anisotropy significantly decreased in the BA wall compared to the BA cavity. In the BA wall, FA and linear anisotropy (CL) showed a significant positive correlation with ICAM-1 and LFA-1 expression whereas FA and planar anisotropy positively correlated with NMs quantified from aspirated pus respectively. Higher FA values in the BA wall compared to BA cavity, even when ICAM-1 and LFA-1 were expressed only in the macrophages and not in the collagen fibers, suggests that a combination of both concentric layers of collagen fibers as well as neutrophils and macrophages provide structural orientation and are responsible for increased FA. In the BA wall, increased CL was found compared to the cavity, indicating the presence of concentrically laid collagen fibers responsible for the diffusion of water molecules in the direction parallel to the collagen fibers. We conclude that in the BA, different mechanisms are operative for the changes in the DTI metrics in the wall and cavity; these conclusions are validated by histology and immunohistochemistry.

Correlation of diffusion tensor imaging with histology in the developing human frontal cerebrum.

Transient early cerebral laminar organization resulting from normal developmental events has been revealed in human beings through histology and imaging studies. DTI studies have postulated that the fractional anisotropy (FA)-based differentiation of different laminar structures reflects both differing cellular density over the glial fibers and fiber alignment in respective regions. The aim of this study was to correlate FA values in these transient zones with histology. Brain DTI was performed on 50 freshly aborted human fetuses with gestational ages (GA) ranging from 12 to 42 weeks. Regions of interest were placed on the cortical plate, subplate, intermediate and germinal matrix (GMx) zones of the frontal lobe to quantify FA values. Glial fibrillary acidic protein (GFAP), neurofilament (NF) and neuron-specific enolase (NSE) immunohistochemical analyses were performed for the cortical plate, intermediate zone and GMx. In the cortical plate, a significant positive correlation was observed between FA values and percentage area of GFAP expression in fetuses