Significant Differences In Fractional Anisotropy Research Articles

Diffusion-tensor magnetic resonance imaging in patients with consequences of obstetric brachial plexus palsy

BACKGROUND: Diffusion-tensor magnetic resonance imaging allows visualizing the conductive pathways of the brain and spinal cord and assessing their structure and integrity and has found wide application in practical medicine. Currently, brachial plexus diffusion-tensor magnetic resonance imaging is not a routine research technique, and very few studies have described its use in children and adolescents. AIM: This study aimed to evaluate the possibility of brachial plexus diffusion-tensor magnetic resonance imaging application in pediatric patients with obstetric brachial plexus palsy sequelae and identify correlations between the diffusion-tensor magnetic resonance imaging parameters of brachial plexus and parameters of electrophysiological study of the upper extremities in these patients. MATERIALS AND METHODS: A complex examination of 50 patients was performed. The main group included 30 patients aged 6–17 years, with contractures and secondary deformities of the bones of the shoulder girdle and upper limbs caused by unilateral obstetric brachial plexus palsy. The control group included 20 patients aged 7–17 (10.1 ± 2.1) years without clinical signs, and anamnestic data indicated the presence of damage to the brachial plexus and peripheral nerves of the upper limbs. RESULTS: No significant differences in diffusion-tensor magnetic resonance imaging parameters of the right and left brachial plexus were found in the control group. Significant differences in fractional anisotropy of the C5–C8 tracts on the side of the damaged brachial plexus were detected compared with those on the side of the undamaged brachial plexus. On the side of the injured brachial plexus, nonlinear correlations were found between the fractional anisotropy of the tracts of the spinal nerve and its branches and the amplitude of sensory responses from the sensory nerve, which originated from the anterior branches of this spinal nerve, and between the volume of the branches of the tracts of the spinal nerve and the amplitude of соmpound motor responses from the muscles, which were innervated by the anterior branches of this spinal nerve. CONCLUSIONS: Diffusion-tensor magnetic resonance imaging allows for the evaluation of the structural changes in the SNs that participate in the formation of the brachial plexus. The results can be used for further studies of diffusion-tensor magnetic resonance imaging of brachial plexuses in various pathologies in pediatric patients.

Short fiber bundle filtering and test-retest reproducibility of the Superficial White Matter.

In recent years, there has been a growing interest in studying the Superficial White Matter (SWM). The SWM consists of short association fibers connecting near giry of the cortex, with a complex organization due to their close relationship with the cortical folding patterns. Therefore, their segmentation from dMRI tractography datasets requires dedicated methodologies to identify the main fiber bundle shape and deal with spurious fibers. This paper presents an enhanced short fiber bundle segmentation based on a SWM bundle atlas and the filtering of noisy fibers. The method was tuned and evaluated over HCP test-retest probabilistic tractography datasets (44 subjects). We propose four fiber bundle filters to remove spurious fibers. Furthermore, we include the identification of the main fiber fascicle to obtain well-defined fiber bundles. First, we identified four main bundle shapes in the SWM atlas, and performed a filter tuning in a subset of 28 subjects. The filter based on the Convex Hull provided the highest similarity between corresponding test-retest fiber bundles. Subsequently, we applied the best filter in the 16 remaining subjects for all atlas bundles, showing that filtered fiber bundles significantly improve test-retest reproducibility indices when removing between ten and twenty percent of the fibers. Additionally, we applied the bundle segmentation with and without filtering to the ABIDE-II database. The fiber bundle filtering allowed us to obtain a higher number of bundles with significant differences in fractional anisotropy, mean diffusivity, and radial diffusivity of Autism Spectrum Disorder patients relative to controls.

Diffusion tensor imaging of hamstring muscles after acute strain injury and throughout recovery in collegiate athletes.

To identify the region of interest (ROI) to represent injury and observe between-limb diffusion tensor imaging (DTI) microstructural differences in muscle following hamstring strain injury. Participants who sustained a hamstring strain injury prospectively underwent 3T-MRI of bilateral thighs using T1, T2, and diffusion-weighted imaging at time of injury (TOI), return to sport (RTS), and 12 weeks after RTS (12wks). ROIs were using the hyperintense region on a T2-weighted sequence: edema, focused edema, and primary muscle injured excluding edema (no edema). Linear mixed-effects models were used to compare diffusion parameters between ROIs and timepoints and limbs and timepoints. Twenty-four participants (29 injuries) were included. A significant ROI-by-timepoint interaction was detected for all diffusivity measures. The edema and focused edema ROIs demonstrated increased diffusion at TOI compared to RTS for all diffusivity measures (p-values < 0.006), except λ1 (p-values = 0.058-0.12), and compared to 12wks (p-values < 0.02). In the no edema ROI, differences in diffusivity measures were not observed (p-values > 0.82). At TOI, no edema ROI diffusivity measures were lower than the edema ROI (p-values < 0.001) but not at RTS or 12wks (p-values > 0.69). A significant limb-by-timepoint interaction was detected for all diffusivity measures with increased diffusion in the involved limb at TOI (p-values < 0.001) but not at RTS or 12wks (p-values > 0.42). Significant differences in fractional anisotropy over time or between limbs were not detected. Hyperintensity on T2-weighted imaging used to define the injured region holds promise in describing muscle microstructure following hamstring strain injury by demonstrating between-limb differences at TOI but not at follow-up timepoints.

Machine learning research based on diffusion tensor images to distinguish between anorexia nervosa and bulimia nervosa.

Anorexia nervosa (AN) and bulimia nervosa (BN), two subtypes of eating disorders, often present diagnostic challenges due to their overlapping symptoms. Machine learning has proven its capacity to improve group classification without requiring researchers to specify variables. The study aimed to distinguish between AN and BN using machine learning models based on diffusion tensor images (DTI). This is a cross-sectional study, drug-naive females diagnosed with anorexia nervosa (AN) and bulimia nervosa (BN) were included. Demographic data and DTI were collected for all patients. Features for machine learning included Fractional anisotropy (FA), axial diffusivity (AD), radial diffusivity (RD), and mean diffusivity (MD). Support vector machine was constructed by LIBSVM, MATLAB2013b, and FSL5.0.9 software. A total of 58 female patients (24 AN, 34 BN) were included in this study. Statistical analysis revealed no significant differences in age, years of education, or course of illness between the two groups. AN patients had significantly lower BMI than BN patients. The AD model exhibited an area under the curve was 0.793 (accuracy: 75.86%, sensitivity: 66.67%, specificity: 88.23%), highlighting the left middle temporal gyrus (MTG_L) and the left superior temporal gyrus (STG_L) as differentiating brain regions. AN patients exhibited lower AD features in the STG_L and MTG_L than BN. Machine learning analysis indicated no significant differences in FA, MD, and RD values between AN and BN groups (p > 0.001). Machine learning based on DTI could effectively distinguish between AN and BN, with MTG_L and STG_L potentially serving as neuroimaging biomarkers.

Significance of Corticospinal, Associative and Inter-Hemispheric Tracts for the Development of Posttraumatic Hemiparesis

Motor disorders are among the most common consequences of severe craniocerebral injury (traumatic brain injury — TBI). Deeper insights into pathophysiological mechanisms of these disorders is important both from a theoretical point of view and in terms of improving neurorehabilitation approaches.The aim of the study was to investigate the correlation of right–sided posttraumatic hemiparesis severity with composite characteristics of fractional anisotropy (FA) in the segments of the corpus callosum (CC), corticospinal tract (CST) and the inferior fronto-occipital fasciculus (IFO) at different stages of traumatic disease (acute, subacute and long-term periods).Material and methods. Cases of 43 patients with TBI were analyzed (28 men and 15 women aged 13 to 59 years, mean age 28±9 years). Forty patients were diagnosed with severe TBI with diffuse axonal damage, three patients had moderate severity TBI. Long-term follow up included continuous clinical and neurological examination with evaluation of patient’s level of consciousness using the CRS-R scale, and the degree of motor deficits in right-sided hemiparesis using a five-point scale. During three post-TBI periods (up to 1 month, from 1 to 6 months, and from 6 to 12 months), patients were examined using diffusion tensor MRI (DTI), tractography and FA. Motor, cortico-spinal tracts and IFO were divided by measurement grid, correlations between FA and scores of right-sided hemiparesis were calculated for each segment.Results. FA correlations (P0.05) with the severity of hemiparesis were established not only for CST motor-specific segments, but also for some CC and IFO segments. In the early period of TBI significant correlations with hemiparesis severity were found not only in the contralateral CST segments, but also in the ipsilateral ones. Significant differences in FA in the related CC and CST segments were found between the groups with good and limited motor recovery: at all stages after TBI, FA was higher in patients with successful recovery.Conclusion. The results of the study provide better insight into pathophysiological mechanisms of post-traumatic motor disorders development, therefore favoring optimization of therapeutic strategies.

Bilateral anterior corona radiata microstructure organisation relates to impaired social cognition in schizophrenia

ObjectiveThe Corona Radiata (CR) is a large white matter tract in the brain comprising of the anterior CR (aCR), superior CR (sCR), and posterior CR (pCR), which have associations with cognition, self-regulation, and, in schizophrenia, positive symptom severity. This study tested the hypothesis that the microstructural organisation of the aCR, as measured by Fractional Anisotropy (FA) using Diffusion Tensor Imaging (DTI), would relate to poorer social cognitive outcomes and higher positive symptom severity for people with schizophrenia, when compared to healthy participants. We further hypothesised that increased positive symptoms would relate to poorer social cognitive outcomes. MethodsData were derived from n = 178 healthy participants (41 % females; 36.11 ± 12.36 years) and 58 people with schizophrenia (30 % females; 42.4 ± 11.1 years). The Positive and Negative Symptom Severity Scale measured clinical symptom severity. Social Cognition was measured using the Reading the Mind in the Eyes Test (RMET) Total Score, as well as the Positive, Neutral, and Negative stimuli valence. The ENIGMA-DTI protocol tract-based spatial statistics (TBSS) was used. ResultsThere was a significant difference in FA for the CR, in individuals with schizophrenia compared to healthy participants. On stratification, both the aCR and pCR were significantly different between groups, with patients showing reduced white matter tract microstructural organisation. Significant negative correlations were observed between positive symptomatology and reduced microstructural organisation of the aCR. Performance for RMET negative valence items was significantly correlated bilaterally with the aCR, but not the sCR or pCR, and no relationship to positive symptoms was observed. ConclusionsThese data highlight specific and significant microstructural white-matter differences for people with schizophrenia, which relates to positive clinical symptomology and poorer performance on social cognition stimuli. While reduced FA is associated with higher positive symptomatology in schizophrenia, this study shows the specific associated with anterior frontal white matter tracts and reduced social cognitive performance. The aCR may have a specific role to play in frontal-disconnection syndromes, psychosis, and social cognitive profile within schizophrenia, though further research requires more sensitive, specific, and detailed consideration of social cognition outcomes.

2 Cognitive Sparing in Proton Versus Photon Radiotherapy for Pediatric Brain Tumor Associated with White Matter Integrity

Objective:Radiotherapy for pediatric brain tumor is associated with reduced white matter structural integrity and neurocognitive decline. Superior cognitive outcomes have been reported following proton radiotherapy (PRT) compared to conventional photon radiotherapy (XRT), presumably due to sparing of healthy brain tissue. This study examined long-term white matter change and neuropsychological performance in pediatric brain tumor survivors treated with XRT vs. PRT.Participants and Methods:Pediatric brain tumor survivors treated with either XRT (n = 10) or PRT (n = 12) underwent neuropsychological testing and diffusion weighted imaging &gt; 7 years following radiotherapy. A healthy control group (n = 23) was also recruited. Groups had similar demographic characteristics, except for handedness (p = .01), mean years of age at testing (XRT = 21.7, PRT = 16.9, Control = 15.5; p = .01), and mean years since radiation (XRT =14.7, PRT = 8.9, p &lt; .001). Age and handedness were selected as covariates; analyses were not adjusted for time since radiation due to redundancy with treatment group (i.e., standard of care transitioned from XRT to PRT in 2007). Participants completed age-appropriate versions of the Weschler Intelligence Scales (WAISIV/WISC-IV/WISC-V) and the Beery-Buktenica Developmental Test of Visual-Motor Integration (VMI and Motor Coordination subtests). Tractography was conducted using automated fiber quantification (AFQ), and fractional anisotropy (FA) was extracted from 12 tracts of interest. Linear mixed models were used to summarize group differences in FA, with tracts nested within subjects. Neuropsychological performance and tract-level FA were compared between groups using analysis of covariance (ANCOVA). Pearson correlation was used to examine associations between cognitive functioning and tract-level FA.Results:Across all tracts, FA was significantly lower in the XRT group than the PRT group (t(514) = -2.58, p = .01), but did not differ between PRT and Control groups (t(514) = .65, p = .51). For individual tracts, FA differed significantly between treatment groups (XRT &lt; PRT) in the left inferior fronto-occipital fasciculus (IFOF), right IFOF, left inferior longitudinal fasciculus (ILF) and right uncinate (all t &lt; -2.05, all p &lt; .05). No significant differences in FA were found between PRT and Control participants for any tract. All neuropsychological scores were significantly lower for XRT than PRT patients (all p &lt; .03), while PRT and Control groups performed similarly on these measures (all p &gt;.19). Cognitive functioning was most consistently associated with FA of the corpus callosum major forceps (4/7 domains; all r &gt; .33, all p &lt; .04) and the left ILF (4/7 domains; all r &gt; .37, all p &lt;.02).Conclusions:Both white matter integrity and neuropsychological performance were generally reduced in patients with a history of XRT, but not in those who received PRT. The PRT group was similar to healthy control participants with respect to both FA and cognitive scores, suggesting improved long-term outcomes compared to patients receiving XRT. This exploratory study is the first to provide direct support for white matter integrity as a mechanism of cognitive sparing in PRT. Future work with larger samples is necessary to replicate these findings.

48 Sex Differences and Longitudinal Changes in White Matter Microstructure in Healthy Older Adults

Objective:As the global population of older adults increases, it is crucial to study the healthy aging brain. Despite representing approximately 50% of brain tissue, investigations of changes in white matter (WM) have been limited. Given that women outlive men in most populations worldwide, evaluating factors such as sex and gender in the normal aging trajectory are particularly important. However, past research has been limited by varying definitions of these terms and methodological challenges. Further, limited studies have employed longitudinal designs. The objective of the present study was to 1) compare sex similarities and differences in WM microstructure, and 2) investigate longitudinal changes in WM in healthy older adults. The Parkinson’s Progression Markers Initiative (PPMI) is an ongoing observational longitudinal study designed to investigate biomarkers related to Parkinson’s disease. For up-to-date information, please see: https://www.ppmi-info.org/. The PPMI study presents a convenient opportunity to investigate the expected aging trajectory among healthy older adults by using data from its healthy control cohort.Participants and Methods:Participants (N=40) included 16 females (mean age = 60.50 + 5.99) and 24 males (mean age = 65.50 + 7.53) from the healthy control cohort of the PPMI. Diffusion tensor imaging (DTI) data from two time points (baseline and approximately one year later) were analyzed using tract-based spatial statistics from the FMRIB Software Library (FSL). Diffusion weighted images were acquired with a Siemens 3T TIM Trio scanner with a 12 channel Matrix head coil. All images were acquired with a spin echo, echo planar imaging sequence with 64 gradient directions and a b-value of 1000s/mm2 with a voxel size of 2 mm3. Two analyses were conducted: 1) between-groups, comparing differences in WM microstructure between males and females at baseline while controlling for age and total brain volume (TBV), and 2) within-subject, examining longitudinal changes in WM from baseline to one year later. DTI metrics included fractional anisotropy (FA) and mean diffusivity (MD).Results:Males were significantly older than females and had significantly larger TBVs. Results of voxelwise comparisons revealed no statistically significant differences in FA or MD between males and females when controlling for age and TBV. Longitudinally over one year, decreases in MD (p&lt;.05, corrected) were found in the right superior and inferior longitudinal fasciculus, the right corticospinal tract, and the right inferior fronto-occipital fasciculus. Stability in FA was observed over one year. There was also an average of a one-point decline on the Montreal Cognitive Assessment during the study period of one year.Conclusions:No significant sex differences in WM microstructure were found, which agrees with a published review of the literature that men and women show very similar brain structure after accounting for brain size differences. Across the entire sample, longitudinal changes in WM were captured via neuroimaging across a one-year time frame. Follow-up exploration of these data suggests great intraindividual variability in trajectories over time, which may have affected the overall group trajectory. Continued research of factors that contribute to the identifying individual healthy aging trajectories is warranted.

To explore the pathogenesis of Bell's palsy using diffusion tensor image

To explore the pathogenesis of Bell's palsy using the diffusion tensor image on 3.0 T MR. The healthy people and the patients with Bell's palsy underwent intraparotid facial nerve scanning by using the DTI and T1 structural sequence at 3.0 T MR. The raw DTI data were performed affine transformation and nonlinear registration in the common MNI152_T1 space and resampled to the 0.4 mm3 voxel size. A group of 4 spherical seed regions were placed on the intratemporal facial nerves in the common space, bilaterally and symmetrically. The DTI data in the common space were used to track the intratemporal facial nerve fibers by using TrackVis and its Diffusion Toolkit. Each tractography was used to construct the maximum probability map (MPM) according to the majority rule. The fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD) and radial diffusivity (RD) were calculated and extracted on the basis of MPM. For healthy people, there was no significant difference in FA, MD, RD and AD of bilateral facial nerves. For patients with Bell's palsy, there was no significant difference in AD, there was significant difference in FA, MD and RD between the affected nerve and the healthy nerve (P < 0.02). This study showed that the myelin sheath injury of the intratemporal facial nerve is the main cause of Bell's palsy. Most neural axons are not damaged. The results may explain the pathogenesis of the Bell's palsy, which is self-limited for most cases.

Microstructural Changes in Normal-Appearing White Matter in Pediatric X-Linked Adrenoleukodystrophy: A Diffusion Tensor Imaging Study

Abstract Objective Diffusion tensor imaging (DTI) is an advanced magnetic resonance imaging (MRI) technique that provides quantitative diffusion data of water molecules in tissue. Usage of DTI in pediatric X-linked adrenoleukodystrophy (X-ALD) may adjunct earlier detection of brain involvement. This study aimed to analyze the normal-appearing white matter in pediatric patients with X-ALD using DTI. Materials and Methods A retrospective database search was performed. Children with genetically diagnosed X-ALDs with a reportedly normal brain MRI between January 2010 and September 2021 were included. Fractional anisotropy (FA), radial diffusivity (RD), axial diffusivity (AD), and apparent diffusion coefficient were serially measured in 8 regions of the brain, and these measurements were compared with those in control patients. Results The study group included 21 X-ALD patients and 11 control patients. The mean age was 6.64 ± 5.14 years. FA values of the genu and body of the corpus callosum were significantly lower in the ALD group than controls. There was also a statistically significant difference in FA, AD, and RD values of cerebellar white matter in the two groups. Conclusion There is evidence of white matter damage on DTI in X-ALD patients with the normal-appearing white matter on conventional MRI sequences. The inclusion of DTI in routine MRI examinations of X-ALD patients may provide additional insight into possible white matter damage in that population.

Application of TBSS-based machine learning models in the diagnosis of pediatric autism.

To explore the microstructural changes of white matter in children with pediatric autism by using diffusion kurtosis imaging (DKI), and evaluate whether the combination of tract-based spatial statistics (TBSS) and back-propagation neural network (BPNN)/support vector machine (SVM)/logistic regression (LR) was feasible for the classification of pediatric autism. DKI data were retrospectively collected from 32 children with autism and 27 healthy controls (HCs). Kurtosis fractional anisotropy (FAK), mean kurtosis (MK), axial kurtosis (KA), radial kurtosis (RK), fractional anisotropy (FA), axial diffusivity (DA), mean diffusivity (MD) and Radial diffusivity (DR) were generated by iQuant workstation. TBSS was used to detect the regions of parameters values abnormalities and for the comparison between these two groups. In addition, we also introduced the lateralization indices (LI) to study brain lateralization in children with pediatric autism, using TBSS for additional analysis. The parameters values of the differentiated regions from TBSS were then calculated for each participant and used as the features in SVM/BPNN/LR. All models were trained and tested with leave-one-out cross validation (LOOCV). Compared to the HCs group, the FAK, DA, and KA values of multi-fibers [such as the bilateral superior longitudinal fasciculus (SLF), corticospinal tract (CST) and anterior thalamic radiation (ATR)] were lower in pediatric autism group (p < 0.05, TFCE corrected). And we also found DA lateralization abnormality in Superior longitudinal fasciculus (SLF) (the LI in HCs group was higher than that in pediatric autism group). However, there were no significant differences in FA, MD, MK, DR, and KR values between HCs and pediatric autism group (P > 0.05, TFCE corrected). After performing LOOCV to train and test three model (SVM/BPNN/LR), we found the accuracy of BPNN (accuracy = 86.44%) was higher than that of LR (accuracy = 76.27%), but no different from SVM (RBF, accuracy = 81.36%; linear, accuracy = 84.75%). Our proposed method combining TBSS findings with machine learning (LR/SVM/BPNN), was applicable in the classification of pediatric autism with high accuracy. Furthermore, the FAK, DA, and KA values and Lateralization index (LI) value could be used as neuroimaging biomarkers to discriminate the children with pediatric autism or not.

Using Diffusion Tensor Imaging to Explore the Changes in the Microstructure of Canine Vocal Fold Scar Tissue

To apply diffusion tensor imaging (DTI) in measurement of the diffusion characteristics of water molecules in vocal fold scar tissue, combined with the analysis of textural characteristics of collagen fibers in the cover layer of the vocal folds to explore the feasibility of DTI in the qualitative and quantitative diagnosis of vocal fold scars and the evaluation of microstructural changes of vocal fold scar tissue. A unilateral injury was created using micro-cup forceps in the left vocal fold of six beagles. The contralateral normal vocal fold was used as a self-control. Five months postinjury, the larynges were excised and placed into a magnetic resonance imaging (MRI) system (9.4T BioSpec MRI, Bruker, German) for scanning and extraction of the diffusion parameters, fractional anisotropy (FA) and tensor trace in the anterior, middle, and posterior portions of the vocal fold cover layer. These parameters were then analyzed for statistical significance between the scarred vocal fold and the normal vocal fold. After MRI scanning, the tissue of the vocal folds was divided into anterior, middle, and posterior parts for sectioning and staining with hematoxylin and eosin, and samples were subsequently digitally scanned for texture analysis. The irregularity parameters, energy, contrast, correlation, and homogeneity, of collagen fibers of the vocal folds and the mean gray value of collagen fibers were calculated by the gray-level co-occurrence matrix (GLCM) texture analysis method. The differences in the mean value of the two sides of the vocal fold were compared. In addition, Pearson correlation analysis was performed between DTI parameters and irregularity parameters. The FA of the left vocal fold cover layer was significantly lower compared to the self-control group (P=0.0366), and the tensor trace value on the left vocal fold cover layer was significantly higher compared to the self-control group (P=0.0353). The FA was significantly higher in the anterior part of the right vocal fold cover layer compared to the middle and posterior parts of the same side (P=0.0352), and the tensor trace was significantly lower in the anterior part of the right vocal fold cover layer compared to the middle and posterior parts of the same side (P=0.0298). There were no significant differences in FA and tensor trace between the middle and posterior parts of the vocal fold cover layer. The mean gray value of the left vocal folds cover layer was significantly smaller than the right vocal fold cover layer (P=0.0219), the energy of the left vocal fold cover layer was significantly smaller than that of the right vocal fold cover layer (P < 0.0001), the contrast of the left vocal folds cover layer was significantly larger than that of the right vocal fold cover layer (P=0.0002), the correlation of the left vocal folds cover layer was significantly smaller than the right vocal fold cover layer (P=0.0002), and the homogeneity of the left vocal folds cover layer was significantly smaller than the right vocal fold cover layer (P=0.0003). Pearson correlation analysis yielded values of r=0.926, P=0.000 between the FA and mean gray value; r=-0.918, P=0.000 between FA and energy; r=-0.924, P=0.000 between the FA and homogeneity, r=-0.949, P=0.000 between tensor trace and mean gray value; r=0.893, P=0.000 between the tensor trace and energy; and r=0.929, P=0.000 between the tensor trace and homogeneity. FA and tensor trace can be used as effective parameters to reflect microstructural changes in vocal fold scars. DTI is an objective and quantitative method of analyzing vocal fold scarring, and it noninvasively evaluates the microstructure of vocal fold collagen fibers.

Diffusion Tensor Imaging in Syringomyelia Secondary to Chiari Malformation in Cavalier King Charles Spaniel—A Preliminary Study

Syringomyelia secondary to Chiari-like malformation (so-called CM-SM syndrome) is a common disorder in Cavalier King Charles Spaniels (CKCS) that is diagnosed using standard structural MRI, though imaging findings often do not correlate with the severity of clinical symptoms. Diffusion tensor imaging (DTI) is a technique that defines subtle microstructural changes in the course of many brain and spinal cord diseases, that are not visible on standard MRI. The aim of the study was to identify the correlation between the presence of clinical symptoms and DTI parameters, such as apparent diffusion coefficient (ADC) and fractional anisotropy (FA) within the spinal cord in the course of CM-SM. Study subjects included 18 dogs, CKCS with MRI-confirmed SM (SM group), and 12 CKCS dogs without SM (non-SM group). The SM group was divided into SM-symptomatic group (n = 8) and SM-asymptomatic group, n = 10). All dogs underwent same clinical and neurological assessment followed by MRI examination. All MRI studies were performed on a 1.5T MRI scanner. The MRI spine protocol included: transverse and sagittal T2-weighted images followed by DTI performed in the sagittal plane. The measurements of FA and ADC values were performed manually using the region of interest (ROI) method at the level of three intervertebral discs between C1 and C4. Notable differences in age and body weight were found. No significant differences in FA and ADC values between the SM and non-SM groups were found, but between non-SM, SM-asymptomatic and SM-symptomatic groups significant differences were found in ADC values in all three ROIs and in FA values in ROI-1 and ROI-3. SM-symptomatic dogs compared to non-SM, showed decreased FA value in ROI-1 and ROI-3 also increased ADC value in ROI-1, ROI-2 and ROI-3. SM-symptomatic dogs compared to SM-asymptomatic showed also decreased FA value in ROI-1 and ROI-3, and also increased ADC value in ROI-1, ROI-2 and ROI-3. The results suggest that the values of DTI parameters correlate with the severity of clinical symptoms in the course of CM-SM in animals. The use of DTI evaluation of CM-SM patients carries a potential value as a clinically relevant protocol for an objective assessment of the spinal cord.

Levodopa responsiveness and white matter alterations in Parkinson's disease: A DTI-based study and brain network analysis: A cross-sectional study.

Patients with Parkinson's disease (PD) present various responsiveness to levodopa, but the cause of such differences in levodopa responsiveness is unclear.Previous studies related the damage of brain white matter (WM) to levodopa responsiveness in PD patients, but no study investigated the relationship between the structural brain network change in PD patients and their levodopa responsiveness. PD patients were recruited and evaluated using the Unified Parkinson's Disease Rating Scale (UPDRS). Each patient received a diffusion tensor imaging (DTI) scan and an acute levodopa challenge test. The improvement rate of UPDRS-III was calculated. PD patients were grouped into irresponsive group (improvement rate<30%) and responsive group (improvement rate ≥ 30%). Tract-based spatial statistics (TBSS), deterministic tracing (DT), region of interest (ROI) analysis, and automatic fiber identification (AFQ) analyses were performed.The structural brain network was also constructed and the topological parameters were calculated. Fifty-four PD patients were included. TBSS identified significant differences in fractional anisotropy (FA) values in the corpus callosum and other regions of the brain. DT and ROI analysis of the corpus callosum found a significant difference in FA between the two groups. Graph theory analysis showed statistical differences in global efficiency, local efficiency, and characteristic path length. PD patients with poor responsiveness to levodopa had WM damage in multiple brain areas, especially the corpus callosum, which might cause disruption of information integration of the structural brain network.

Cross-site harmonization of multi-shell diffusion MRI measures based on rotational invariant spherical harmonics (RISH)

Quantification methods based on the acquisition of diffusion magnetic resonance imaging (dMRI) with multiple diffusion weightings (e.g., multi-shell) are becoming increasingly applied to study the in-vivo brain. Compared to single-shell data for diffusion tensor imaging (DTI), multi-shell data allows to apply more complex models such as diffusion kurtosis imaging (DKI), which attempts to capture both diffusion hindrance and restriction effects, or biophysical models such as NODDI, which attempt to increase specificity by separating biophysical components. Because of the strong dependence of the dMRI signal on the measurement hardware, DKI and NODDI metrics show scanner and site differences, much like other dMRI metrics. These effects limit the implementation of multi-shell approaches in multicenter studies, which are needed to collect large sample sizes for robust analyses. Recently, a post-processing technique based on rotation invariant spherical harmonics (RISH) features was introduced to mitigate cross-scanner differences in DTI metrics. Unlike statistical harmonization methods, which require repeated application to every dMRI metric of choice, RISH harmonization is applied once on the raw data, and can be followed by any analysis. RISH features harmonization has been tested on DTI features but not its generalizability to harmonize multi-shell dMRI. In this work, we investigated whether performing the RISH features harmonization of multi-shell dMRI data removes cross-site differences in DKI and NODDI metrics while retaining longitudinal effects. To this end, 46 subjects underwent a longitudinal (up to 3 time points) two-shell dMRI protocol at 3 imaging sites. DKI and NODDI metrics were derived before and after harmonization and compared both at the whole brain level and at the voxel level. Then, the harmonization effects on cross-sectional and on longitudinal group differences were evaluated. RISH features averaged for each of the 3 sites exhibited prominent between-site differences in the frontal and posterior part of the brain. Statistically significant differences in fractional anisotropy, mean diffusivity and mean kurtosis were observed both at the whole brain and voxel level between all the acquisition sites before harmonization, but not after. The RISH method also proved effective to harmonize NODDI metrics, particularly in white matter. The RISH based harmonization maintained the magnitude and variance of longitudinal changes as compared to the non-harmonized data of all considered metrics. In conclusion, the application of RISH feature based harmonization to multi-shell dMRI data can be used to remove cross-site differences in DKI metrics and NODDI analyses, while retaining inherent relations between longitudinal acquisitions.

Difference in the ascending reticular activating system between vegetative and minimally conscious states following traumatic brain injury.

ObjectivesWe investigated differences in the ascending reticular activating system (ARAS) between vegetative state (VS) and minimally conscious state (MCS) in patients with traumatic brain injury (TBI) by using diffusion tensor tractography.MethodsWe recruited TBI patients and normal subjects. We reconstructed the lower ARAS and five parts of upper ARAS [prefrontal cortex (PFC), premotor cortex, primary motor cortex, primary somatosensory cortex, and posterior parietal cortex].ResultsSignificant differences were observed in the fractional anisotropy (FA) and fiber number (FN) values of the five parts of upper ARAS between the VS and control groups and between the MCS and control groups (P < 0.05), but no differences were detected in the lower ARAS (P > 0.05). The FA and FN values of the PFC in the upper ARAS were significantly different between the VS and MCS groups (P < 0.05). No other significant differences in FA and FN values were detected among the other segments of the upper ARAS or in the lower ARAS (P > 0.05).ConclusionThe results indicate that the prefrontal portion of the upper ARAS is the critical area for distinguishing between VS and MCS in patients with TBI.

2.1 LIMBIC MICROSTRUCTURE AND CONNECTIVITY MARKERS OF ATTENTIONAL DEFICITS IN YOUTH AT RISK FOR BIPOLAR DISORDER

Although symptoms of ADHD and having a biological parent with bipolar disorder (BD) are risk factors for developing BD, neural biomarkers of risk are poorly understood. We used diffusion tensor imaging (DTI) and resting-state functional connectivity (RSFC) to compare limbic microstructure and connectivity among youth with ADHD with (high-risk [HR]) and without (low-risk [LR]) a family history of BD and a healthy comparison group. Three groups of psychostimulant-free youth (ages 10-18 years) were recruited: 1) HR youth with ADHD and a first-degree relative with BD (HR); 2) LR youth with ADHD and no first-degree relative with a mood disorder (LR); and 3) healthy comparison youth (HC). Diffusion-weighted and resting-state echo-planar images were collected using a Philips 3.0 T MR scanner. Fractional anisotropy (FA) and mean diffusivity (MD) maps were calculated. Bilateral amygdala were used as the seeds to estimate connectivity. Multiple-comparisons correction was determined using Monte Carlo simulations using AlphaSim (p < 0.05 and voxels ≥40). A total of 105 youth (61% male; mean [SD] age of 14.5 [2.5] years; HR, n = 31; LR, n = 38; HC, n = 36) were recruited. Group comparisons revealed significant FA differences in bilateral insular cortex and right cuneus and MD differences in the left inferior frontal gyrus. Post hoc analyses revealed that the LR group has increased FA in the bilateral insula, right anterior cingulum, bilateral putamen, right caudate, and right cuneus, and increased MD in the bilateral inferior frontal gyri, left amygdala, and right hippocampus. HR youth exhibit increased FA in the bilateral insula and the left superior and inferior temporal cortex, and increased MD in the right amygdala, bilateral inferior frontal gyri, and right medial frontal gyrus. RSFC analyses revealed that HR exhibited greater right amygdala to right ventrolateral prefrontal cortex (R-VLPFC) connectivity compared with both HC (p < 0.001) and LR (p = 0.017) youth. Altered microstructure in the dorsal striatum was present in youth with ADHD and not in youth with attention deficits who are at risk for developing BD. Right amygdala-VLPFC resting-state hyperconnectivity distinguish youth at risk for BD and may represent a prodromal risk biomarker for bipolar disorder.

Impaired white matter microstructure associated with severe depressive symptoms in patients with PD.

Depression is a common occurrence in patients with Parkinson's disease (PD); however, its pathophysiology is still unclear. This study assessed the association between the integrity of white matter and depressive symptoms in patients with PD. 67 patients with PD were divided into a non-depressed PD group (ndPD, n = 30) and a depressed PD group (dPD, n = 37). The dPD group was further subdivided into a mild-moderately depressed PD (mdPD, n = 22) and a severely depressed PD group (sdPD, n = 15). Tract-Based Spatial Statistics was used to compare fractional anisotropy (FA) between groups. Region-of-interest analysis was used to explore changes in diffusivity indices in the regions showing FA abnormalities. The sdPD patients exhibited significantly reduced FA in the left superior longitudinal fasciculus, uncinate fasciculus, anterior corona radiata, corticospinal tract, and bilateral inferior fronto-occipital fasciculus when compared with the ndPD patients, but the decreased FA was within a smaller area when compared with the mdPD patients. No significant difference in FA was found between the mdPD and ndPD groups. Among the dPD patients, FA values in the left superior longitudinal fasciculus negatively correlated with BDI scores. Impaired white matter integrity in the prefronto-limbic/temporal circuitry, mainly in the left hemisphere, is associated with severe, but not mild-moderate depressive symptoms in patients with PD.

Abnormal interhemispheric resting state functional connectivity in Parkinson\u2019s disease patients with impulse control disorders

Impulse control disorders (ICD) in Parkinson’s disease (PD) might be attributed to misestimate of rewards or the failure to curb inappropriate choices. The mechanisms underlying ICD were reported to involve the lateralization of monoamine network. Our objective was to probe the significant role of lateralization in the pathogenesis of ICD. Twenty-one PD patients with ICD (PD-ICD), thirty-three without ICD (PD-no ICD), and thirty-seven healthy controls (HCs) were recruited and performed T1-weighted, diffusion tensor imaging (DTI) scans and resting state functional magnetic resonance imaging (rs-fMRI). By applying the Voxel-mirrored Homotopic Connectivity (VMHC) and Freesurfer, we evaluated participants’ synchronicity of functional connectivity and structural changes between hemispheres. Also, tract-based spatial statistics (TBSS) was applied to compare fiber tracts differences. Relative to PD-no ICD group, PD-ICD group demonstrated reduced VMHC values in middle frontal gyrus (MFG). Compared to HCs, PD-ICD group mainly showed decreased VMHC values in MFG, middle and superior orbital frontal gyrus (OFG), inferior frontal gyrus (IFG) and caudate, which were related to reward processing and inhibitory control. The severity of impulsivity was negatively correlated with the mean VMHC values of MFG in PD-ICD group. Receiver operating characteristic (ROC) curves analyses uncovered that the mean VMHC values of MFG might be a potential marker identifying PD-ICD patients. However, we found no corresponding asymmetrical alteration in cortical thickness and no significant differences in fractional anisotropy (FA) and mean diffusivity (MD). Our results provided further evidence for asymmetry of functional connectivity in mesolimbic reward and response inhibition network in ICD.

Analysis of Age-Related White Matter Microstructures Based on Diffusion Tensor Imaging.

Population aging has become a serious social problem. Accordingly, many researches are focusing on changes in brains of the elderly. In this study, we used multiple parameters to analyze age-related changes in white matter fibers. A sample cohort of 58 individuals was divided into young and middle-age groups and tract-based spatial statistics (TBSS) were used to analyze the differences in fractional anisotropy (FA), mean diffusion (MD), axial diffusion (AD), and radial diffusion (RD) between the two groups. Deterministic fiber tracking was used to investigate the correlation between fiber number and fiber length with age. The TBSS analysis revealed significant differences in FA, MD, AD, and RD in multiple white matter fibers between the two groups. In the middle-age group FA and AD were lower than in young people, whereas the MD and RD values were higher. Deterministic fiber tracking showed that the fiber length of some fibers correlated positively with age. These fibers were observed in the splenium of corpus callosum (SCC), the posterior limb of internal capsule (PLIC), the right posterior corona radiata (PCR_R), the anterior corona radiata (ACR), the left posterior thalamic radiation (include optic radiation; PTR_L), and the left superior longitudinal fasciculus (SLF_L), among others. The results showed that the SCC, PLIC, PCR_R, ACR, PTR_L, and SLF_L significantly differed between young and middle-age people. Therefore, we believe that these fibers could be used as image markers of age-related white matter changes.