Diffusion Tensor Imaging MRI Research Articles

Combinatorial Anatomic and Functional Neural Tract Mapping for Stereotactic Radiosurgery Planning.

IntroductionStereotactic radiosurgery (SRS) is effective and safe for the treatment of the vast majority of brain metastases (BMs). SRS is increasingly used for the simultaneous treatment of multiple lesions, retreatment of recurrence, or subsequent treatment of new lesions. Although radiation injury is relatively uncommon, with the increased utilization of SRS, it is imperative to develop approaches to assess and mitigate radiation-induced neurologic toxicity. Multiple factors influence the development of radiation injury, including patient age, genomic variations, prior treatment, dose and volume treated, and anatomic location. Functional neural structure proximity to SRS targets is a critical factor in developing a systematic integrated risk assessment for SRS patients.MethodsWe developed an approach for risk assessment based on the combinatorial application of i) the anatomic localization of target lesions using a reference neuroanatomical/functional imaging atlas merged with patient-specific imaging and ii) validation with functional MRI (fMRI) and diffusion tensor imaging MRI (DTI-MRI) to identify neural tracts.ResultsIn the case of a thalamic/midbrain junction breast carcinoma metastasis, the reference image analysis revealed proximity to the corticospinal tract (CST), which was validated by functional DTI-MRI. Dose-volume exposure of the CST could be estimated and considered in the development of a final treatment plan.ConclusionMerging pretreatment MR imaging with neuroanatomical/functional reference MRIs and subsequent validation with fMRI or DTI-MRI may prove to be a valuable approach to screen for neural risks in individual SRS patients. Incorporating this approach in larger studies could further our understanding of dose tolerances in a broad range of neural structures.

Whole-Brain Functional and Diffusion Tensor MRI in Human Participants with Metallic Orthodontic Braces.

Background MRI performed with echo-planar imaging (EPI) sequences is sensitive to susceptibility artifacts in the presence of metallic objects, which presents a substantial barrier for performing functional MRI and diffusion tensor imaging (DTI) in patients with metallic orthodontic material and other head implants. Purpose To evaluate the ability to reduce susceptibility artifacts in healthy human participants wearing metallic orthodontic braces for two alternative approaches: T2-prepared functional MRI and diffusion-prepared DTI with three-dimensional fast gradient-echo readout. Materials and Methods In this prospective study conducted from February to September 2018, T2-prepared functional MRI and diffusion-prepared DTI were performed in healthy human participants. Removable dental braces with bonding trays were used so that MRI could be performed with braces and without braces in the same participants. Results were evaluated in regions with strong (EPI dropout regions for functional MRI and the inferior fronto-occipital fasciculus for DTI) and minimal (motor cortex for functional MRI and the posterior limb of internal capsule for DTI) susceptibility artifacts. Signal-to-noise ratio (SNR), contrast-to-noise ratio for functional MRI, apparent diffusion coefficient and fractional anisotropy for DTI, and degree of distortion (quantified with the Jaccard index, which measures the similarity of geometric shapes) were compared in regions with strong or minimal susceptibility effects between the current standard EPI sequences and the proposed alternatives by using paired t test. Results Six participants were evaluated (mean age ± standard deviation, 40 years ± 6; three women). In brain regions with strong susceptibility effects from the metallic braces, T2-prepared functional MRI showed significantly higher SNR (37.8 ± 2.4 vs 15.5 ± 5.3; P < .001) and contrast-to-noise ratio (0.83 ± 0.16 vs 0.29 ± 0.10; P < .001), whereas diffusion-prepared DTI showed higher SNR (5.8 ± 1.5 vs 3.8 ± 0.7; P = .03) than did conventional EPI methods. Apparent diffusion coefficient and fractional anisotropy were consistent with the literature. Geometric distortion was substantially reduced throughout the brain with the proposed methods (significantly higher Jaccard index, 0.95 ± 0.12 vs 0.81 ± 0.61; P < .001). Conclusion T2-prepared functional MRI and diffusion-prepared diffusion tensor imaging can acquire functional and diffusion MRI, respectively, in healthy human participants wearing metallic dental braces with less susceptibility artifacts and geometric distortion than with conventional echo-planar imaging. © RSNA, 2019 Online supplemental material is available for this article. See also the editorial by Dietrich in this issue.

Non-invasive assessment of early stage diabetic nephropathy by DTI and BOLD MRI.

Patients with diabetes mellitus, diabetic nephropathy (DN) and healthy donor were analyzed to test whether the early DN patients can be detected using both blood oxygenation level dependent (BOLD) and diffusion tensor imaging. This study was approved by the Ethics Committee of our hospital. MR images were acquired on a 3.0-Tesla MR system (Discovery MR750, General Electric, Milwaukee, WI). 30 diabetic patients were divided into NAU (normal to mildly increased albuminuria, N = 15) and MAU (moderately increased albuminuria, N = 15) group based on the absence or presence of microalbuminuria. 15 controls with sex- and age-matched were enrolled in the study. Prior to MRI scan, all participants were instructed to collect their fresh morning urine samples for quantitative measurement of urinary microalbumin and urinary creatinine. Then, the estimations of serum creatinine, serum uric acid, HbAlc and fasting plasma glucose as well as fundus examinations were performed in all subjects. Then, the values of albumin-creatinine ratio (ACR) and estimated glomerular filtration rate were also calculated. All subjects underwent renal diffusion tensor imaging (DTI) and BOLD acquisition after fasting for 4 h. Regions of interest were placed in renal medulla and cortex for evaluating apparent diffusion coefficient (ADC), fractional anisotropy (FA) and R2* values by two experienced radiologists. The consistency between the two observations was estimated using intragroup correlation coefficients. To test differences in ADC, FA and R2* values across the three groups, the data were analyzed using separate one-way ANOVAs. Post-hoc pair wise comparisons were then performed using t-test. To investigate the clinical relevance of imaging parameters in both regions across the three groups, the correlations of values of the ACR/estimated glomerular filtration rate and of the ADC/FA/R2* were calculated. There was a high level of consistency of those ADC, FA and R2* values across the three groups on both renal cortex and medulla measured by the two doctors. The FA value of medulla in MAU group was lower than that in control (p < 0.01). The R2* value of medulla in the NAU group was higher than that in the control (p < 0.01), and the R2* value of medulla in the MAU group was lower than that in the control (p = 0.009) . Moreover, the current study revealed a decreasing trend in FA values of the renal medulla from the control group to NAU and MAU groups. Finally, a weak negatively correlation between medullary R2* and ACR was found in current study. Medullary R2* value might be a new more sensitive predictor of early DN. Meanwhile, BOLD imaging detected the medullary hypoxia at the simply diabetic stage, while DTI didn't identify the medullary directional diffusion changes at this stage. Based on our assumption mentioned above, it's presumable that BOLD imaging may be more sensitive for assessment of the early renal function changes than DTI. These imaging techniques are more accurate and practical than conventional tests. Non-invasive MRI was used to detect renal function changes at early DN stage.

Diffusion tensor imaging for assessment of normally appearing white matter of the brain and spinal cord in cases of multiple sclerosis: a multi-parametric correlation in view of patient\u2019s clinical status

BackgroundConventional MRI provides important morphologic information regarding the brain and spinal cord involvement by demyelinating plaques. However, it is of almost no value in assessing the normal-appearing white matter which has been proved by multiple pathologic studies to be directly and indirectly involved in the process of multiple sclerosis. Diffusion-weighted imaging and diffusion tensor imaging MRI have been widely used in multiple researches as a better solution for studying the normal-appearing white matter. The purpose of this study was to evaluate the role of diffusion tensor imaging examination of the normal-appearing white matter of the brain and spinal cord in patients with multiple sclerosis and to determine the relationship between diffusion tensor imaging metrics and patient’s clinical status.ResultsThe significant negative correlation found between expanded disability status scale score of secondary progressive MS patients and global (brain and spinal cord) average fractional anisotropy values in normal-appearing white matter and tracts (P = 0.000). Correlation between average apparent diffusion coefficient of corpus callosum tract and expanded disability status scale score revealed a significant positive correlation in RRMS (P = 0.001). While in secondary progressive MS, a significant negative correlation between fractional anisotropy average of the corpus callosum tract and expanded disability status scale score was noted (P = 0.015).ConclusionThere is a strong relationship between diffusion tensor imaging readings and clinical status of patients can be used to understand unexplained deterioration over disease course and also can be used when conventional MRI findings are equivocal. Corpus callosum affection in MS patients is intimately related to clinical status and its assessment should be done whenever possible.

Structural and functional reorganization following unilateral internal capsule infarction contribute to neurological function recovery.

To investigate proliferative reorganization in the bilateral corticospinal tract (CST) and functional reorganization in the sensorimotor network (SMN) after internal capsule stroke, and to examine the significance of this reorganization. We recruited 17 patients with first-onset acute stroke (16 male, 1 female, mean age 52 ± 10years) and 17 age- and sex-matched healthy controls. We excluded patients aged < 18 or > 65years and those with lesions outside the unilateral internal capsule. All subjects underwent diffusion tensor imaging and resting-state functional MRI on days 7, 30, and 90 from symptom onset. We measured fractional anisotropy (FA) in the CST, interhemispheric functional connectivity (FC) within the SMN, and pre-MRI clinical scores, including the National Institutes of Health Stroke Scale (NIHSS), Barthel Index (BI), and Fugl-Meyer (FM). Correlations among the changes in FA, FC, and clinical scores were analyzed. From day 7 to 90 after stroke, FA in the bilateral CST increased (ipsilesional side, Pinternal capsule = 0.009, Pcentrum semiovale = 0.001; contralesional side, Pinternal capsule = 0.006, Pcentrum semiovale = 0.017), as did FC (P < 0.05); NIHSS scores decreased (P < 0.05), while FM and BI progressively increased (P < 0.05). Increased FA in bilateral CST was negatively correlated with decreased NIHSS scores. Increased FA in only the ipsilesional side was positively correlated with increased FM. Increased FC was positively correlated only with increased BI. Proliferative reorganization in the CST and functional reorganization in the SMN support and promote neurological functional recovery after internal capsule infarction.

Fiber Tractography and Diffusion Tensor Imaging in Children with Agenesis and Dysgenesis of Corpus Callosum: A Clinico-Radiological Correlation

Background Corpus callosum is the largest commissure in human brain. It consists of tightly packed white matter tracts connecting the two cerebral hemispheres. In this study we aimed to evaluate role of fiber tractography (FT), and diffusion tensor imaging (DTI) in pediatric patients with corpus callosum anomalies and correlate findings with clinical presentation. Materials and Methods This prospective study included 115 children with clinical presentations and CT findings suggested corpus callosum anomalies. Their ages ranged between 2 and 12 year-old. They referred from Pediatric Neurology unit to Radiology Department in Minia University hospital for children, Minia (Egypt) from April 2018 till December 2018. They underwent MRI fiber tractography and diffusion tensor imaging after approval of ethical committee of our institution and informed consent form patients’ parents. Results Our study included 42 (36.5 %) males and 73 (63.5 %) females. They were reviewed for corpus callosum anomalies according to Hanna classification, the commonest was hypoplasia without dysplasia 37/115 (32 %). Using DTI and FT, corpus callosum fiber defects were classified into fronto-rostral, caudal and whole body defect. Significant statistical correlation was found between ADHD, autism and loss of fronto-rostral fibers. Epilepsy and developmental delay were correlated to whole body defect and caudal fiber tract defects. Conclusion Based on the results, Fiber tractography and diffusion tensor imaging are newly developed promising techniques. They proved high accuracy in localization of exact affected corpus callosum white matter tract. They help to predict prognosis of patients that could not be explained by morphological changes seen in conventional MRI.

The role of hippocampal subfield volume and fornix microstructure in episodic memory across the lifespan.

Advancing age is associated with both declines in episodic memory and degradation of medial temporal lobe (MTL) structure. The contribution of MTL to episodic memory is complex and depends upon the interplay among hippocampal subfields and surrounding structures that participate in anatomical connectivity to the cortex through inputs (parahippocampal and entorhinal cortices) and outputs (fornix). However, the differential contributions of MTL system components in mediating age effects on memory remain unclear. In a sample of 177 healthy individuals aged 20-94 we collected high-resolution T1-weighted, ultrahigh-resolution T2/PD, and diffusion tensor imaging (DTI) MRI sequences on a 3T Phillips Achieva scanner. Hippocampal subfield and entorhinal cortex (ERC) volumes were measured from T2/PD scans using a combination of manual tracings and training of a semiautomated pipeline. Parahippocampal gyrus volume was estimated using Freesurfer and DTI scans were used to obtain diffusion metrics from tractography of the fornix. Item and associative episodic memory constructs were formed from multiple tests. Competing structural equation models estimating differential association among these structural variables were specified and tested to investigate whether and how fornix diffusion and volume of parahippocampal gyrus, ERC, and hippocampal subfields mediate age effects on associative and/or item memory. The most parsimonious, best-fitting model included an anatomically based path through the MTL as well as a single hippocampal construct which combined all subfields. Results indicated that fornix microstructure independently mediated the effect of age on associative memory, but not item memory. Additionally, all regions and estimated paths (including fornix) combined to significantly mediate the age-associative memory relationship. These findings suggest that preservation of fornix connectivity and MTL structure with aging is important for maintenance of associative memory performance across the lifespan.

Blood Perfusion and Cellular Microstructural Changes Associated With Iron Deposition in Multiple Sclerosis Lesions

Background and Purpose: Susceptibility-weighted imaging (SWI) has emerged as a useful clinical tool in many neurological diseases including multiple sclerosis (MS). This study aims to investigate the relationship between SWI signal changes due to iron deposition in MS lesions and tissue blood perfusion and microstructural abnormalities to better understand their underlying histopathologies.Methods: Forty-six patients with relapsing remitting MS were recruited for this study. Conventional FLAIR, pre- and post-contrast T1-weighted imaging, SWI, diffusion tensor imaging (DTI), and dynamic susceptibility contrast (DSC) perfusion MRI were performed in these patients at 3T. The SWI was processed using both magnitude and phase information with one slice minimal intensity projection (mIP) and phase multiplication factor of 4. MS lesions were classified into 3 types based on their lesional signal appearance on SWI mIP relative to perilesional normal appearing white matter (peri-NAWM): Type-1: hypointense, Type-2: isointense, and Type-3: hyperintense lesions. The DTI and DSC MRI data were processed offline to generate DTI-derived mean diffusivity (MD) and fractional anisotropy (FA) maps, as well as DSC-derived cerebral blood flow (CBF) and cerebral blood volume (CBV) maps. Comparisons of diffusion and perfusion measurements between lesions and peri-NAWM, as well between different types of lesions, were performed.Results: A total of 137 lesions were identified on FLAIR in these patients that include 40 Type-1, 46 Type-2, and 51 Type-3 lesions according to their SWI intensity relative to peri-NAWM. All lesion types showed significant higher MD and lower FA compared to their peri-NAWM (P < 0.0001). Compared to Type-1 lesions (likely represent iron deposition), Type-2 lesions had significantly higher MD and lower FA (P < 0.001) as well as lower perfusion measurements (P < 0.05), while Type 3 lesions had significantly higher perfusion (P < 0.001) and lower FA (P < 0.05). Compared to Type-2, Type-3 lesions had higher perfusion (P < 0.0001) and marginally higher MD and lower FA (P < 0.05).Conclusion: The significant differences in diffusion and perfusion MRI metrics associated with MS lesions, that appear with different signal appearance on SWI, may help to identify the underlying destructive pathways of myelin and axons and their evolution related to inflammatory activities.

P1‐376: LONG‐TERM NSAID THERAPY IN OLDER ADULTS: EFFECTS ON AT(N)V IMAGING BIOMARKERS

Observational studies and animal model experiments have suggested that the regular use of nonsteroidal anti-inflammatory drugs (NSAIDs) may be protective against Alzheimer's disease (AD). However, randomized controlled trials have not supported this hypothesis. We sought to assess whether long-term use of NSAIDs would be associated with differences in neuroimaging biomarkers of aging and dementia. We analyzed data for adults over 65 years old from the population-based Mayo Clinic Study of Aging. Individuals were classified as NSAID-untreated (n=439) if they reported no regular use of NSAIDs (defined as fewer than 3 days per week) prior to neuroimaging. Individuals who reported taking NSAIDs for 3+ days per week or 5+ years were defined as long-term NSAID-treated (n=519). For these groups, we analyzed the following neuroimaging outcomes based on the A (amyloid)/T (tau)/N (neurodegeneration)/V (cerebrovascular) framework: global amyloid (11C-PiB-PET), global and entorhinal cortex tau (18F-AV-1451-PET), AD-pattern hypometabolism (18F-FDG-PET) and cortical thickness (MRI), and white matter hyperintensities (FLAIR MRI) and fractional anisotropy of the corpus callosum (diffusion tensor imaging MRI). Age and sex were included as covariates in all analyses. Statistical significance was defined as p<0.05. The NSAID-treated group was older (mean age 78.5 vs. 76.1, p<0.001) and more frequently male (61% vs. 46%, p<0.001) than the untreated group. NSAID-treated individuals had a higher burden of late-life cardiovascular and metabolic conditions (p<0.001) but did not differ in APOE ɛ4 allele status, education, or clinical diagnosis (cognitively unimpaired, mild cognitive impairment, dementia) compared to the NSAID-untreated group. Long-term NSAID therapy was not significantly associated with any neuroimaging biomarker analyzed. In this study, we identified no association between long-term NSAID therapy and alterations in AT(N)V neuroimaging biomarkers. Additional work is needed to determine whether aspirin may be associated with differential effects compared to non-aspirin NSAIDs and to assess whether NSAID therapy alters longitudinal biomarker trajectories, particularly in individuals with high burden of cerebrovascular risk factors. As candidates for multi-domain treatment regimens for causes of dementia become available, evaluation of these approaches using AT(N)V biomarkers in the population will allow for rapid and dynamic assessment of potential efficacy and putative mechanism of action.

Patterning of corpus callosum integrity in glioma observed by MRI: Effect of 2D bi-axial lamellar brain architecture.

Corpus callosum (CC) is a main channel histologically for glioma spreading, downgrading the prognosis, the infiltration occurring through cellular reaction-diffusion process. Preliminary clinical trial indicates that CC's surgical interruption appreciably enhances clinical outcome. We aim to find how high-grade glioma phenomenology is reflected in CC parameters, including various 3D diffusion eigenvalues differentially, whereby this information may be utilized for planning radiotherapy and surgical intervention. Using 3 Tesla MRI diffusion-tensor imaging of glioma patients and matched controls, we formulated the callosal volume, fibre count, and 3D directional diffusivity eigenvalues (λ1-λ2-λ3), utilizing FDT/FMRIB-based analysis. In glioma, the callosal volume, fibre count and normalized volume decreases (p < 0.001), while axial diffusivity λ1 and radial diffusivity component λ2 significantly increase (p = 0.03, p = 0.04). Though not expected, the other radial diffusivity component λ3 remains unchanged (p = 0.11). Increase of λ1 and λ2 is due to gliomatous migration across the two directions (eigenvectors of λ1, λ2), which correlate respectively with medio-lateral commissural fibres and dorso-ventral perforating fibres in CC. These are corroborated by collateral radiological findings and immunohistological staining of those two fibre-systems in cat and human. In glioma, the two diffusivities (λ1, λ2), enhance due to fluidic edema permeation through CC's bi-axial lamina-type structural scaffold, formed by mediolateral commissural fibres and dorsoventral perforating cingulo-septal fibres. On other hand, the two radial diffusivities (λ2, λ3) are physiologically different and can be distinguished as lamellar diffusivity and focal diffusivity respectively. Lamellar diffusivity λ2 needs to be considered for MRI-assisted surgical intervention and radiotherapy planning in glioma.

Molecular Senescence Is Associated With White Matter Microstructural Damage in Late-Life Depression

ObjectivesThe authors aim to investigate the association between white matter integrity and accelerated brain aging in late-life depression. MethodsThe authors measured senescence-associated secretory phenotype (SASP) index proteins, cognitive performance, and MRI diffusion tensor imaging (DTI) measures of fractional anisotropy and mean diffusivity-based indices of white matter microstructure measures in 56 older adults with remitted late-life depression. ResultsHigher SASP index was significantly correlated with older age (r = 0.42, p = 0.001) and worse executive function performance (r = −0.27, p = 0.04). After controlling for the effect of age, overall cognitive performance, and white matter hyperintensities, the association between SASP and left and right cingulate bundle mean diffusivity remained statistically significant. ConclusionsOur data suggest that, in the context of late-life depression, SASP proteins are associated with microstructural abnormalities in white matter tracts in brain and worse executive function performance.

A multimodal MRI-based classification signature emerges just prior to symptom onset in frontotemporal dementia mutation carriers

BackgroundMultimodal MRI-based classification may aid early frontotemporal dementia (FTD) diagnosis. Recently, presymptomatic FTD mutation carriers, who have a high risk of developing FTD, were separated beyond chance level from controls...

Progressive agrammatic aphasia without apraxia of speech as a distinct syndrome.

Agrammatic aphasia affects grammatical language production and can result from a neurodegenerative disease. Although it typically presents with concomitant apraxia of speech, this is not always the case. Little is known about the clinical course and imaging features of patients that present with agrammatism in the absence of apraxia of speech, which we will refer to as progressive agrammatic aphasia. We aimed to make a detailed description of the longitudinal clinical, linguistic, and neuroimaging features of a cohort of 11 patients with progressive agrammatic aphasia to provide a complete picture of this syndrome. All patients underwent detailed speech and language, neurological and neuropsychological assessments, 3 T structural and diffusion tensor imaging MRI, 18F-fluorodeoxyglucose and Pittsburgh compound B PET. The 11 patients were matched by age and gender to 22 patients who had mixed apraxia of speech and agrammatism. The progressive agrammatic aphasia patients performed abnormally on tests of language, general cognition, executive function, and functional ability at baseline and declined in these measures over time. Only two patients eventually developed apraxia of speech, while parkinsonism was absent-to-mild throughout all visits for all patients. When compared to the patients with mixed apraxia of speech and agrammatism, the patients with progressive agrammatic aphasia performed better on tests of motor speech and parkinsonism but more poorly, and declined faster over time, on tests of general aphasia severity, agrammatism, and naming. The patients with progressive agrammatic aphasia also showed different neuroimaging abnormalities, with greater atrophy, hypometabolism and white matter tract degeneration in the prefrontal and anterior temporal lobes compared to patients with mixed apraxia of speech and agrammatism. These differences were more pronounced as the disease progressed. These results demonstrate that progressive agrammatic aphasia has a different clinical disease course and different underlying neuroanatomical abnormalities than patients with the more common syndrome of mixed agrammatism and apraxia of speech. This supports the distinction of progressive agrammatic aphasia and has implications for the classification of patients with agrammatic aphasia.

Comparison between quantitative measurements of diffusion tensor imaging and T2 signal intensity in a large series of cervical spondylotic myelopathy patients for assessment of disease severity and prognostication of recovery.

Cervical spondylotic myelopathy (CSM) is a common cause of spinal cord dysfunction. Recently, it has been shown that diffusion tensor imaging (DTI) may be a better biomarker than T2-weighted signal intensity (T2SI) on MRI for CSM. However, there is very little literature on a comparison between the quantitative measurements of DTI and T2SI in the CSM patient population to determine disease severity and recovery. A prospective analysis of 46 patients with both preoperative DTI and T2-weighted MRI was undertaken. Normalized T2SI (NT2SI), regardless of the presence or absence of T2SI at the level of maximum compression (LMC), was determined by calculating the T2SI at the LMC/T2SI at the level of the foramen magnum. Regression analysis was performed to determine the relationship of fractional anisotropy (FA), a quantitative measure derived from DTI, and NT2SI individually as well their combination with baseline preoperative modified Japanese Orthopaedic Association (mJOA) score and ∆mJOA score at the 3-, 6-, 12-, and 24-month follow-ups. Goodness-of-fit analysis was done using residual diagnostics. In addition, mixed-effects regression analysis was used to evaluate the impact of FA and NT2SI individually. A p value < 0.05 was selected to indicate statistical significance. Regression analysis showed a significant positive correlation between FA at the LMC and preoperative mJOA score (p = 0.041) but a significant negative correlation between FA at the LMC and the ΔmJOA score at the 12-month follow-up (p = 0.010). All other relationships between FA at the LMC and the baseline preoperative mJOA score or ∆mJOA score at the 3-, 6-, and 24-month follow-ups were not statistically significant. For NT2SI and the combination of FA and NT2SI, no significant relationships with preoperative mJOA score or ∆mJOA at 3, 6, and 24 months were seen on regression analysis. However, there was a significant correlation of combined FA and NT2SI with ∆mJOA score at the 12-month follow-up. Mixed-effects regression revealed that FA measured at the LMC was the only significant predictor of ΔmJOA score (p = 0.03), whereas NT2SI and time were not. Goodness-of-fit analysis did not show any evidence of lack of fit. In this large prospective study of CSM patients, FA at LMC appears to be a better biomarker for determining long-term outcomes following surgery in CSM patients than NT2SI or the combination values at LMC.

What is the Functional Difference Between Sagittal With Metopic and Isolated Sagittal Craniosynotosis?

The purpose of this study is to understand the neurological differences between patients born with combined sagittal and metopic craniosynostosis (SMc) and isolated sagittal craniosynostosis (ISc) by studying aberrations in functional brain connectivity and white matter microstructure, before surgery, utilizing functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI). The authors collected DTI and resting-state (ie, no sedation and asleep) functional connectivity MRI data in 10 infant patients preoperatively: 5 in the SMc group (4.3 ± 1 months) and 5 in the ISc group (4.8 ± 1.1 months). Resting state fMRI imaging and DTI data were acquired using a 3-T Siemens Trio MRI system (Erlangen, Germany) while the infant patients slept. fMRI data were corrected for movement using SPM, underwent cerebrospinal fluid and white matter signal regression and further analyzed with BioImageSuite. For the DTI data, 3 diffusion runs were averaged, processed utilizing FMRIB Software Library, and analyzed statistically using BioImageSuite. Comparing the SMc versus ISc groups, SMc demonstrated that there was increased connectivity, statistically significant differences, in neural networks between children with sagittal synostosis alone versus those with sagittal with metopic synostosis, in the right BA 31 and BA 23 (corresponding to the posterior cingulate cortex (PCC) (P < 0.001). Analysis of the DTI revealed increased fractional anisotropy (normal maturation of white tracts) in the SMc group in the cingulum compared to the ISc group (P < 0.05). Differences in the functional networks include increased connectivity right frontoparietal network (RFPN) in ISc and increased connectivity in the primary visual network (V1) in SMc (P < 0.001). The SMc had increased connectivity as measured by fMR in the PCC, an area associated with attention deficit hyperactivity disorder. The DTI analysis demonstrated an increase in fractional anisotropy of the cingulum in the SMc group, a white matter tract projecting from the cingulate cortex; connections of the limbic (emotional regulation) system are instrumental. In SMc, increase of connectivity in the PCC correlates with an increase in maturation of the cingulum compared to ISc. There is increased connectivity of the RFPN network in the ISc and increased connectivity of the V1 network in the SMc patients. The SMc group has increased connectivity in the PCC, the original seed of the DMN network, and decreased connectivity to the RFPN network. The pattern of increased connectivity in the area of the DMN and decreased connectivity in the RFPN network is similar to the trend when comparing ADHD patients to normal controls. SMc has more similar functional network connectivity to ADHD as compared to ISc.

Diffusion tensor and restriction spectrum imaging reflect different aspects of neurodegeneration in Parkinson's disease.

To meet the need for Parkinson’s disease biomarkers and evidence for amount and distribution of pathological changes, MRI diffusion tensor imaging (DTI) has been explored in a number of previous studies. However, conflicting results warrant further investigations. As tissue microstructure, particularly of the grey matter, is heterogeneous, a more precise diffusion model may benefit tissue characterization. The purpose of this study was to analyze the diffusion-based imaging technique restriction spectrum imaging (RSI) and DTI, and their ability to detect microstructural changes within brain regions associated with motor function in Parkinson’s disease. Diffusion weighted (DW) MR images of a total of 100 individuals, (46 Parkinson’s disease patients and 54 healthy controls) were collected using b-values of 0–4000s/mm2. Output diffusion-based maps were estimated based on the RSI-model combining the full set of DW-images (Cellular Index (CI), Neurite Density (ND)) and DTI-model combining b = 0 and b = 1000 s/mm2 (fractional anisotropy (FA), Axial-, Mean- and Radial diffusivity (AD, MD, RD)). All parametric maps were analyzed in a voxel-wise group analysis, with focus on typical brain regions associated with Parkinson’s disease pathology. CI, ND and DTI diffusivity metrics (AD, MD, RD) demonstrated the ability to differentiate between groups, with strongest performance within the thalamus, prone to pathology in Parkinson’s disease. Our results indicate that RSI may improve the predictive power of diffusion-based MRI, and provide additional information when combined with the standard diffusivity measurements. In the absence of major atrophy, diffusion techniques may reveal microstructural pathology. Our results suggest that protocols for MRI diffusion imaging may be adapted to more sensitive detection of pathology at different sites of the central nervous system.

Structural correlates of the orbitofrontal cortex and amygdala and personality in female adolescents.

The five-factor model consists of cognitive-affective-behavioral trait dimensions (neuroticism, extraversion, openness to experience, agreeableness, conscientiousness) that are central to models of psychopathology. In adults, individual differences in three of the Big Five traits, neuroticism, extraversion, and conscientiousness, have been linked to structural morphology and connectivity of the orbitofrontal cortex (OFC) and the amygdala, two brain regions critically involved in affective and regulatory processing. It is unclear whether these associations manifest in adolescence, a critical neurodevelopmental period during which many forms of psychiatric illness emerge. A total of 223 adolescent girls (ages 14-16years) completed a multimodal neuroimaging study that utilized T1-weighted structural MRI (e.g., cortical thickness and volume) and tractography-based diffusion tensor imaging (64-direction). Cortical thickness and volume were extracted from the medial orbitofrontal cortex (mOFC) and amygdala and tractography-based fractional anisotropy was computed in the uncinate fasciculus (UF; the white matter tract connecting the OFC to the temporal lobe). We found that high neuroticism was associated with less mOFC volume (bilateral), and low conscientiousness was associated with higher white matter integrity in the UF, more amygdala volume, and less mOFC thickness (right hemisphere). Extraversion was not observed to share associations with OFC markers. These OFC-amygdala structural correlations to personality do not match those reported in adult samples. Multimodal neuroimaging techniques can help to clarify the underpinnings of personality development between adolescence and adulthood.

Early Prediction of Functional Outcome after Cerebral Small Arteries Infarctions Using Diffusion Tensor MRI Tractography

AbstractBackground: Lacunar Infarctions (LIs) are ischemic strokes caused by occlusion of the deep penetrating arteries. They constitute about 25% of all ischemic strokes and have variable consequences based on affected tracts disruptions.Aim of Study: Were to assess the role of MRI Diffusion Tensor Imaging (DTI) fiber tractography as an early biomarker of LIs prognosis.Patients and Methods: This work was conducted on 42 first-ever symptomatic motor or sensorimotor LIs patients (3 1 male and 11 female) submitted to stroke severity assess-ment using the National Institute of Health Stroke Scale (NIHSS), carotid duplex, brain MRI to determine LIs dimeter and occult small vessel disease imaging markers. Corticospinal Diffusion Tensor Tractography (CS-DTT) was done within 48 hours from stroke onset. Thirty-eight patients continued a 3-months follow-up schedule, at the end of which their physical dependences were assessed using the Modified Barthel Index (MBI) scale which were compared with the baseline assessment parameters to determine the prognostic biomarkers.Results: Dependent patients' group showed significant increase in their age, BMI, carotid intima media thickness and white matter hyperintensities grade than independent patients' group. The FA ratio was the earliest parameter showed significant changes which were lower in dependent than independent patients' groups. On the other hand, each of ipsilateral DTI fractional anisotropy, mean diffusivity and fiber number showed non-significant differences.Conclusion: Factors associated with poorer functional outcome after newly diagnosed LIs include advanced age, hypertension, obesity, premorbid physical inactivity, increased CIMT and the presence of imaging biomarkers of occult SVD. Reduced ipsilateral/contralateral FA ratio of the CS-DTT is a reliable early predictor of short-term functional outcome and motor disability after motor and sensorimotor LIs.

MRI detects peripheral nerve and adjacent muscle pathology in non-systemic vasculitic neuropathy (NSVN).

Diagnosis and disease monitoring of non-systemic vasculitic neuropathy (NSVN) are based on electrophysiological and clinical measures. However, these methods are insensitive to detect subtle differences of axonal injury. We here assessed the utility of a multiparametric MRI protocol to quantify axonal injury and neurogenic muscle damage in NSVN. Ten NSVN patients and ten age-matched controls were investigated in this single-center prospective study. All participants were assessed by diffusion tensor imaging (DTI) of the tibial nerve and multiecho Dixon MRI of soleus and gastrocnemius muscles. These data were correlated with clinical and electrophysiological data. DTI scans of the tibial nerves of patients with NSVN showed significantly lower mean fractional anisotropy (FA) values (0.32 ± 0.02) compared to healthy controls (0.42 ± 0.01). FA values of NSVN patients correlated negatively with clinical measures of pain. Multiecho Dixon MRI scans revealed significantly higher intramuscular fat fractions in the soleus muscle (19.86 ± 6.18% vs. 5.86 ± 0.74%, p = 0.0015) and gastrocnemius muscle (26.09 ± 6.21% vs. 3.59 ± 0.82%, p = 0.0002) in NSVN patients compared to healthy controls. Our data provide a proof of concept that MRI can render information about nerve integrity and muscle pathology in NSVN. Further studies are warranted to evaluate DTI and multiecho Dixon MRI as surrogate markers in NSVN.

Cognitive impairment in patients with end-stage renal disease: Accelerated brain aging?

Chronic kidney disease exhibits a prominent premature aging phenotype in many different organ systems, including the brain. Nevertheless, a comprehensive characterization of brain aging in non-demented patients with end-stage renal disease (ESRD) is lacking and it remains unclear if the collective changes of cognitive functions and brain structures in ESRD is compatible with aging. We compared 56 non-demented, independently living dialysis patients (mean age 59.4±11.0 years; mean dialysis vintage of 5.9 years) and 60 non-dialysis controls on a battery of neuropsychological tests, brain MRI T1 imaging and diffusion tensor imaging. Participants with diagnosis of dementia, Mini-Mental State Examination <24, medical history of stroke, or recent hospitalization within 1 month were excluded. Dialysis patients showed significantly worse performance in attention/information processing speed and executive function adjusted for age, sex, education, diabetes and depression. Reduced total brain volume and subcortical volume including hippocampus were found in dialysis patients. Vertex-wise analysis showed cortical thinning in middle frontal, lateral occipital and precuneus region. Furthermore, decreased white matter integrity was found primarily in bilateral anterior thalamic tract, fronto-occipital fasciculus, forceps minor and uncinate tract after correction for multiple comparisons. Overall, differences in cognitive functions, cortical volumes/thickness and white matter integrity associated with dialysis are also cognitive domains and brain structure changes associated with normal aging. In other words, non-demented, independently living dialysis patients present an accelerated brain aging phenotype even after taking into account effects of age, diabetes and depression.