For Fractional Anisotropy Values Research Articles

Precision Imaging in Neurodegeneration: The Superiority of Diffusion Tensor Imaging Over Conventional MRI in Differentiating Parkinson's Disease From Atypical Parkinsonian Syndromes.

Background Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized by the degeneration of dopaminergic neurons in the substantia nigra, leading to motor and non-motor symptoms. Atypical parkinsonian syndromes (APS), including progressive supranuclear palsy (PSP) and essential tremor (ET), present with overlapping clinical features, making differential diagnosis challenging. Conventional MRI has limitations in distinguishing PD from APS, necessitating advanced imaging techniques like diffusion tensor imaging (DTI) for more accurate diagnosis. Objectives This retrospective study aimed to evaluate the diagnostic accuracy of DTIin diagnosing PDand APS, particularly assessing its ability to differentiate these conditions from each other compared to conventional MRI. Additionally, the study sought to determine if DTI could diagnose PD in cases where conventional MRI results were normal, thereby highlighting the potential role of DTI in enhancing diagnostic precision in neurodegenerative disorders. Methodology The study included 30 patients with clinically diagnosed PD or APS who underwent both conventional MRI and DTI. Data were collected retrospectively. Imaging was performed using a Philips Multiva 1.5-Tesla MRI scanner (Philips, Amsterdam, Netherlands). DTI sequences were analyzed for fractional anisotropy (FA)values in the substantia nigra, superior cerebellar peduncle, middle cerebellar peduncle, transverse pontine fibers, and dentate nucleus. The FA values were compared with established normal values, and the findings from DTI were correlated with clinical diagnoses and conventional MRI results. Results Among the 30 patients, 53.3% were clinically diagnosed with PDand 46.7% with APS, including PSP and ET. Conventional MRI findings were normal in 46.7% of cases, indicating its limitations in detecting early or subtle changes in neurodegenerative disorders. In contrast, DTI identified abnormalities in 83.3% of cases, demonstrating its superior diagnostic sensitivity. DTI detected significant FA value reductions in the substantia nigra in PD patients (mean FA: 0.440), which is consistent with the degeneration of dopaminergic neurons characteristic of PD. In PSP patients, the superior cerebellar peduncle showed marked FA reductions (mean FA: 0.523), correlating with the clinical features of PSP, such as bradykinesia and postural instability. ET was identified by reduced FA values in the superior cerebellar peduncle and dentate nucleus, distinguishing it from other forms of parkinsonism. DTI was particularly effective in cases where conventional MRI results were inconclusive or normal, identifying early-stage PD and differentiating it from APS with greater accuracy. The study demonstrated a sensitivity of 95.8% and specificity of 93.8% for DTI in differentiating PD from APS compared to conventional MRI. Conclusion This study highlights DTI as a superior imaging modality for the early diagnosis and differentiation of parkinsonian disorders, particularly when conventional MRI results are inconclusive. DTI's ability to detect significant microstructural changes in specific brain regions, evidenced by FA value reductions, enhances diagnostic accuracy. Incorporating DTI into routine clinical practice is essential for accurate differentiation between PD and APS, facilitating better patient management.

Evaluating the therapeutic effect of LIPUS in the early stage of traumatic brain injury using FA and T2* in rats.

To evaluate the protective effect of LIPUS at the early stage of brain trauma in rats, 45 rats were randomly divided into 3 groups: sham (n = 15), TBI (n = 15) and LIPUS treatment groups (n = 15). Ipsilateral and contralateral cortical and thalamic parameters obtained by diffusion tensor imaging (DTI) and fast low-angle shot magnetic resonance imaging (FLASH-MRI) were measured at different times after trauma. For fractional anisotropy (FA) and T2* values, two-way repeated measures ANOVA with Tukey's post hoc was used for intergroup comparisons. With observation time prolonged, the FA values of the ipsilateral cortex in the TBI group gradually increased and were significantly higher than those in the LIPUS treatment group on Day 7 (adjusted P = 0.0067). FA values in the contralateral cortex decreased at this time and were significantly lower than those in the LIPUS treatment group (adjusted P = 0.0192). Meanwhile, compared with LIPUS group, FA values were significantly higher in the injured thalamus (adjusted P = 0.0025). Combined with correlation analysis, FA values were positively correlated with neuronal damage (P = 0.0148, r2 = 0.895). At 7 days after trauma, T2* values in the ipsilateral cortex of the TBI group were significantly lower. After analysis of ferritin content and correlation, we found that T2* values were negatively correlated with ferritin (P = 0.0259, r2 = -0.849). By measuring post-traumatic changes in FA and T2* values, it is possible to demonstrate a neuronal protective effect of LIPUS in the early phase of TBI rats and promote brain rehabilitation.

T1 relaxation and axon fibre configuration in human white matter.

Understanding the effects of white matter (WM) axon fibre microstructure on T1 relaxation is important for neuroimaging. Here, we have studied the interrelationship between T1 and axon fibre configurations at 3T and 7T. T1 and S0 (=signal intensity at zero TI) were computed from MP2RAGE images acquired with six inversion recovery times. Multishell diffusion MRI images were analysed for fractional anisotropy (FA); MD; V1; the volume fractions for the first (f1), second (f2) and third (f3) fibre configuration; and fibre density cross-section images for the first (fdc1), second (fdc2) and third (fdc3) fibres. T1 values were plotted as a function of FA, f1, f2, f3, fdc1, fdc2 and fdc3 to examine interrelationships between the longitudinal relaxation and the diffusion MRI microstructural measures. T1 values decreased with increasing FA, f1 and f2 in a nonlinear fashion. At low FA values (from 0.2 to 0.4), a steep shortening of T1 was followed by a shallow shortening by 6%-10% at both fields. The steep shortening was associated with decreasing S0 and MD. T1 also decreased with increasing fdc1 values in a nonlinear fashion. Instead, only a small T1 change as a function of either f3 or fdc3 was observed. In WM areas selected by fdc1 only masks, T1 was shorter than in those with fdc2/fdc3. In WM areas with high single fibre populations, as delineated by f1/fdc1 masks, T1 was shorter than in tissue with high complex fibre configurations, as segmented by f2/fdc2 or f3/fdc3 masks. T1 differences between these WM areas are attributable to combined effects by T1 anisotropy and lowered FA. The current data show strong interrelationships between T1, axon fibre configuration and orientation in healthy WM. It is concluded that diffusion MRI microstructural measures are essential in the effort to interpret quantitative T1 images in terms of tissue state in health and disease.

483 Radiographic Changes in the Auditory Pathway to Predict Outcomes of Children with Hearing Loss

OBJECTIVES/GOALS: Early diagnosis of congenital sensorineural hearing loss (SNHL) is of paramount importance in preventing speech and language impairment.Diffusion tensor imaging (DTI) MRI can identify brain microstructural changes that may potentially contribute towards prognosticating rehabilitation. METHODS/STUDY POPULATION: We retrospectively reviewed pediatric patients with SNHL who obtained DTI MRI between 2011 and 2019, identifying 16 pediatric patients (age <18 years) with at least moderate asymmetric/bilateral SNHL., and gender-matched controlswithout neurological, developmental, or MRI-based brain macrostructural abnormalities. The following brainstem regions and tracts of the auditory pathway were assessed: superior olivary nucleus (SON), inferior colliculus (IC), ipsilateral tracts between the inferior colliculus and superior olivary nucleus (IC-SON). Diffusion values for bilateral regions and tracts were generated, then averaged to calculate a mean value for fractional anisotropy (FA) and mean diffusivity (MD) for each subject. RESULTS/ANTICIPATED RESULTS: Significant differences were identified in FA values of the SON between the SNHL cohort and controls (0.377±0.056 vs 0.422±0.052; p=0.009). No other FA or MD values were significantly different. In children £5 years, MD was significantly decreased in the SNHL cohort compared to controls in the IC (0.918±0.051 vs 1.120±0.142; p<0.001). In children >5 years, there were no significant differences in MD (1.124±0.198 vs 0.997±0.103; p = 0.119). There were no significant differences in MD or FA in the white matter fibers of the IC-SON tract [applewebdata%3A//720AAF0C-C4CF-459C-A42A-6BAA56C4E4CA#_msocom_2]. DISCUSSION/SIGNIFICANCE: This is the first study to assess microstructural changes in brainstem auditory pathway regions among children with SNHL. Longitudinal studies are warranted to assess the predictive value of DTI imaging for long-term outcomes and prognosticating intervention.

The role of diffusion tensor imaging metrics in machine learning-based characterisation of paediatric brain tumors and their practicality for multicentre clinical assessment

Abstract Aims Magnetic resonance imaging (MRI) is a valuable tool for non-invasive diagnosis of paediatric brain tumours. The rarity of the disease dictates multi-centre studies and imaging biomarkers that are robust to protocol variability. We investigated diffusion tensor MRI (DT-MRI), combined with machine learning, as an aid to diagnosis and evaluated the robustness of the imaging metrics. Method A multi-centre cohort of 52 clinical DT-MRI scans (20 medulloblastomas (MB), 21 pilocytic astrocytomas (PA), 11 ependymomas (EP)) were analysed retrospectively. Histograms for regions of solid tumour for fractional anisotropy (FA), mean diffusivity (MD), pure anisotropic diffusion (q) and pure isotropic diffusion (p) were compared to assess diagnostic capability. Linear discriminate analysis (LDA) was used for classification and validated using leave-one-out-cross-validation (LOOCV). Results Histogram medians for FA, MD, q and p were all different between tumor groups (P<.0001, Kruskal Wallis test). Median MD, p and q values were highest in PA, then EP and lowest in MB (P<.0001, Pairwise Wilcox test). FA median was higher for EP than PA (P=.004) with no significant difference between EP and MB (P=.591). ROC analysis showed that median MD, q and p perform best as a diagnostic marker (AUC= 0.92 to 0.99). LOOCV showed an overall accuracy of the LDA classification, ranging between 67% - 87%. FA values were highly dependent on protocol parameters, whereas pure anisotropic diffusion, q, was not. Conclusion DT-MRI metrics from multi-centre acquisitions can classify paediatric brain tumours. FA is the least robust metric to protocol variability and q provides the most robust quantification of anisotropic behaviour.

Determination of optimum pixel size and slice thickness for tractography and ulnar nerve diffusion tensor imaging at the cubital tunnel using 3T MRI.

Small peripheral nerve tractography is challenging because of the trade-off among resolution, image acquisition time, and signal-to-noise ratio. To optimize pixel size and slice thickness parameters for fiber tractography and diffusion tensor imaging (DTI) of the ulnar nerve at the cubital tunnel using 3T magnetic resonance imaging (MRI). Fifteen healthy volunteers (mean age 30 ± 6.8 years) were recruited prospectively. Axial T2-weighted and DTI scans were acquired, covering the cubital tunnel, using different pixel sizes and slice thicknesses. Three-dimensional (3D) nerve tractography was evaluated for the median number and length of the reconstructed fiber tracts and visual score from 0 to 5. Two-dimensional (2D) cross-sectional DTI was evaluated for fractional anisotropy (FA) values throughout the length of the ulnar nerve. A pixel size of 1.3 mm2 revealed the highest number of reconstructed nerve fibers compared to that of 1.1 mm2 (P = 0.048), with a good visual score. A slice thickness of 4 mm had the highest number of reconstructed nerve fibers and visual score compared with other thicknesses (all P < 0.05). In 2D cross-sectional images, the median FA values were in the range of 0.40-0.63 at the proximal, central, and distal portions of the cubital tunnel. Inter-observer agreement for all parameters was good to excellent. For fiber tractography and DTI of the ulnar nerve at the cubital tunnel, optimal image quality was obtained using a 1.3-mm2 pixel size and 4-mm slice thickness under MR parameters of this study at 3T.

White matter alterations and the conversion to psychosis: A combined diffusion tensor imaging and glutamate 1H MRS study

IntroductionWidespread white matter abnormalities and alterations in glutamate levels have been reported in patients with schizophrenia. We hypothesized that alterations in white matter integrity and glutamate levels in individuals at clinical high risk (CHR) for psychosis are associated with the subsequent development of psychosis. MethodsParticipants included 33 antipsychotic naïve CHR (Female 7/Male 26, Age 19.55 (4.14) years) and 38 healthy controls (Female 10/Male 28, Age 20.92 (3.37) years). Whole brain diffusion tensor imaging for fractional anisotropy (FA) and right frontal white matter proton magnetic resonance spectroscopy for glutamate levels were acquired. CHR participants were clinically followed for 2 years to determine conversion to psychosis. ResultsCHR participants that transitioned to psychosis (N = 7, 21%) were characterized by significantly lower FA values in the posterior thalamic radiation compared to those who did not transition and healthy controls. In the CHR group that transitioned to psychosis only, positive exploratory correlations between glutamate levels and FA values of the posterior thalamic radiation and the retrolenticular part of the internal capsule and a negative correlation between glutamate levels and the cingulum FA values were found. ConclusionThe results of the present study highlight that alterations in white matter structure and glutamate are related with the conversion to psychosis.

Excessive Daytime Sleepiness and Injury of the Ascending Reticular Activating System Following Whiplash Injury.

Objectives: This study investigated injuries of the ascending reticular activating system (ARAS) following whiplash injury, in patients with excessive daytime sleepiness (EDS).Methods: Twenty-three patients with whiplash injury and 26 healthy control subjects were recruited for this study. Epworth Sleepiness Scale (ESS) was used for evaluating sleepiness. According to the ESS score, the patients were classified into two groups: subgroup A – ESS score <10, and subgroup B – ESS score ≥10. Three components of the ARAS (lower dorsal, lower ventral, and upper) were evaluated for fractional anisotropy (FA) and tract volume (TV).Results: No significant differences were observed in the FA and TV values of the lower dorsal and upper ARAS between the patient and control groups (p > 0.05). Conversely, the values of FA and TV in the lower ventral ARAS of the patient group were significantly lower than those of the control group (p < 0.05). Comparing the values of subgroups A and B, the TV value of subgroup B was significantly lower than subgroup A (p < 0.05). However, no significant differences were observed in the values of the FA and TV in the lower dorsal and upper ARAS, and the FA value in the lower ventral ARAS (p > 0.05).Conclusions: We found significant injury of the lower ventral ARAS in EDS patients with whiplash injury. These results suggest that diffusion tensor tractography (DTT) could provide useful information for detecting injuries of the ARAS following whiplash injury, in patients with EDS.

Dietary Iron Repletion following Early-Life Dietary Iron Deficiency Does Not Correct Regional Volumetric or Diffusion Tensor Changes in the Developing Pig Brain.

Iron deficiency is the most common micronutrient deficiency worldwide and children are at an increased risk due to the rapid growth occurring during early life. The developing brain is highly dynamic, requires iron for proper function, and is thus vulnerable to inadequate iron supplies. Iron deficiency early in life results in altered myelination, neurotransmitter synthesis, neuron morphology, and later-life cognitive function. However, it remains unclear if dietary iron repletion after a period of iron deficiency can recover structural deficits in the brain. Twenty-eight male pigs were provided either a control diet (CONT; n = 14; 23.5 mg Fe/L milk replacer) or an iron-deficient diet (ID; n = 14; 1.56 mg Fe/L milk replacer) for phase 1 of the study, from postnatal day (PND) 2 until 32. Twenty pigs (n = 10/diet from phase 1) were used in phase 2 of the study from PND 33 to 61, all pigs were provided a common iron sufficient diet, regardless of their early-life dietary iron status. All pigs remaining in the study were subjected to magnetic resonance imaging (MRI) at PND 32 and again at PND 61 using structural imaging sequences and diffusion tensor imaging (DTI) to assess volumetric and microstructural brain development, respectively. Data were analyzed using a two-way ANOVA to assess the main and interactive effects of early-life iron status and time. An interactive effect was observed for absolute whole brain volumes, in which whole brain volumes of ID pigs were smaller at PND 32 but were not different than CONT pigs at PND 61. Analysis of brain region volumes relative to total brain volume indicated interactive effects (i.e., diet × day) in the cerebellum, olfactory bulb, and putamen-globus pallidus. Main effects of early-life iron status, regardless of imaging time point, were noted for decreased relative volumes of the left hippocampus, right hippocampus, thalamus, and increased relative white matter volume in ID pigs compared with CONT pigs. DTI indicated interactive effects for fractional anisotropy (FA) in the whole brain, left cortex, and right cortex. Main effects of early-life iron status, regardless of imaging time point, were observed for decreased FA values in the caudate, cerebellum, and internal capsule in ID pigs compared with CONT pigs. All comparisons described above were significant at P < 0.05. Results from this study indicate that dietary iron repletion is able to compensate for reduced absolute brain volumes early in life; however, microstructural changes and altered relative brain volumes persist despite iron repletion.

Abstract WP442: Diffusion Tensor Imaging of White Matter Tracts in Transient Ischemic Attack Patients

Introduction: Transient ischemic attack (TIA) greatly increases the risk of developing dementia later in life. Measurement of microstructural changes in white matter (WM) using diffusion tensor imaging (DTI) tractography has potential for identifying those at greatest risk of cognitive decline. We hypothesized that patients presenting with TIA have abnormal DTI measures in major WM tracts. Our objective was to determine changes in DTI measures for fractional anisotropy (FA) and medial diffusivity (MD) in frontoparietal (Superior Longitudinal Fasciculus; SF) and medial temporal (Uncinate Fasciculus; UF) WM tracts for TIA patients and healthy controls. Methods: Patients presenting with symptoms of high risk TIA but free of dementia, and healthy volunteer controls were recruited acutely. Structural MRI, inclusive of DTI sequences (31 directions b1000) was performed. FA and MD values were collected in the left and right SLF and UF. Multiple linear regression was performed to determine predictors of DTI values (FA and MD), adjusted for age. Subject’s cognition was screened using Montreal Cognitive Assessment (MoCA). Results: Data from 60 TIA patients (mean age = 68.75 years, SD = 9.39, 45% female) and 33 healthy controls (mean age = 64.97 years, SD = 10.45, 67% female) was analyzed. Linear regression identified that TIA patients have higher FA values in left SLF, F(2, 90) = 9.210, p &lt; .001, R 2 = .170); right SLF, F(2, 90) = 7.154, p = .001, R 2 = .137; and left UF, F(2, 90) = 3.513, p = .034, R 2 = .072, compared to healthy controls. No group changes in MD were observed when corrected for age. TIA patients (median score 24, (interquartile range (IQR) = 5) performed worse than healthy controls (median score = 27, IQR = 4) on the MoCA while controlling for age, F(1, 90) = 7.689, p &lt; .007. Conclusion: TIA patients showed changes in FA of WM tracts related to language and memory function when compared to healthy controls, supporting the presence of incipient microstructural disease. Our results show that measures of microstructural changes using DTI may help identify TIA patients at a greater risk of developing cognitive impairment. Future work aims to identify deterioration of DTI measures over time and their relation to potential vascular and neurodegenerative etiologies.

Insight and white matter fractional anisotropy in first-episode schizophrenia

Impaired insight is a hallmark feature of schizophrenia. Structural studies implicate predominantly prefrontal, cingulate, cuneus/precuneus, and inferior temporal brain regions. The cortical midline structures (CMS) are also implicated in functional studies primarily through self-reflective processing tasks. However, few studies have explored the relationship between white matter tracts and insight in schizophrenia, and none in first-episode schizophrenia (FES). Here, we examined for fractional anisotropy (FA) differences in 89 minimally treated FES patients and 98 matched controls, and identified those FA differences associated with impaired clinical insight in patients. We found widespread FA reduction in FES patients compared to controls. Poorer insight in patients was predicted by lower FA values in a number of white matter tracts with a predilection for tracts associated with cortical midline structures (fronto-occipital, cingulate, cingulate hippocampus, uncinate, anterior corona radiata), and more severe depressive symptoms. The association between FA abnormalities and insight was most robust for the awareness of symptoms and illness awareness domains. Our study implicates a network of tracts involved in impaired insight in schizophrenia with a predilection for the CMS. This study is a first step in delineating the white matter tracts involved in insight impairment in schizophrenia prior to chronicity.

The structural connectivity pathology of first-episode schizophrenia based on the cardinal symptom of auditory verbal hallucinations

Heterogeneous findings across studies of structural abnormality in schizophrenia (SZ) have impeded the development a unified theory of white matter pathology. As a cardinal symptom of SZ, auditory verbal hallucination (AVH) has been suspected to be associated with improper communication among several brain regions, which might indicated white matter pathology. Participants comprised 25 first-episode (FE) patients with AVH, 25 patients without AVH and 25 healthy subjects. Diffusion tensor imaging (DTI) measures were calculated using the TBSS of FSL. Voxel-based ANOVA tests were performed among the three groups and threshold-free cluster enhancement (TFCE) method correction was used for multiple comparisons. Voxel-based one-way ANOVA showed significant group effects for fractional anisotropy (FA) and radial diffusivity (RD) values. Post-hoc t-tests indicated that schizophrenia patients had lower FA and higher RD values in the internal capsule and anterior corona radiata than control subjects. Post-hoc analyses exhibited more widespread fiber disruptions in AVH patients than non-AVH patients. These results hinted on the important role of projection fiber disruption in schizophrenia patients. In addition, the current study also suggested that direct comparison between studies using patients with different symptom profiles should be interpreted with caution.

Brain white matter integrity in heroin addicts during methadone maintenance treatment is related to relapse propensity.

IntroductionCognitive deficits caused by heroin‐induced white matter (WM) impairments hinder addicts' engagement in and benefit from treatment. The predictive value of WM integrity in heroin addicts during methadone maintenance treatment (MMT) for future relapse is unclear.MethodsForty‐eight MMT patients were given baseline diffusion tensor imaging scans and divided into heroin relapsers (HR, 25 cases) and abstainers (HA, 23 cases) according to the results of 6‐month follow‐up. Intergroup comparisons were performed for fractional anisotropy (FA), radial diffusivity (RD), and axial diffusivity (AD). The correlation between diffusion tensor imaging indices and the degree of heroin relapse was analyzed.ResultsCompared with HA group, HR group had reduced FA in the right retrolenticular part, left anterior and posterior limb of internal capsule, bilateral anterior corona radiata, and right external capsule. Three out of the six regions showed increased RD, with no changes in AD. The FA and AD values in the left posterior limb of internal capsule correlated negatively with the heroin‐positive urinalysis rate within follow‐up.ConclusionsLower WM integrity in MMT patients may add to neurobiological factors associated with relapse to heroin use. Strategies for improving WM integrity provide a new perspective to prevent future relapse to heroin abuse.

Age-Related Differences in White Matter Integrity in Healthy Human Brain: Evidence from Structural MRI and Diffusion Tensor Imaging.

The aim is to investigate the relationship between microstructural white matter (WM) diffusivity indices and macrostructural WM volume (WMV) among healthy individuals (20–85 years). Whole-brain diffusion measures were calculated from diffusion tensor imaging using FMRIB software library while WMV was estimated through voxel-based morphometry, and voxel-based analysis was carried out using tract-based spatial statistics. Our results revealed that mean diffusivity, axial diffusivity, and radial diffusivity had shown good correlation with WMV but not for fractional anisotropy (FA). Voxel-wise tract-based spatial statistics analysis for FA showed a significant decrease in four regions for middle-aged group compared to young-aged group, in 22 regions for old-aged group compared to middle-aged group, and in 26 regions for old-aged group compared to young-aged group (P < 0.05). We found significantly lower WMV, FA, and mean diffusivity values in females than males and inverted-U trend for FA in males. We conclude differential age- and gender-related changes for structural WMV and WM diffusion indices.

Alterations in white matter integrity in first-episode, treatment-naive patients with somatization disorder

White matter (WM) abnormality in somatization disorder (SD) has not been reported yet. This study was designed to elucidate the alterations in WM integrity in SD. A total of 25 patients with SD and 28 healthy controls were enrolled in the study. WM integrity was analyzed using tract-based spatial statistics. No differences were found between the patients and the controls for fractional anisotropy (FA) values, mean diffusivity (MD), axial diffusivity, and radial diffusivity values at the corrected p<0.05 level. Patients with SD had significantly decreased FA values in the cingulum and inferior fronto-occipital fasciculus, and significantly increased MD values in the anterior thalamic radiation and corticospinal tract compared with the controls at the uncorrected p<0.005 level. Somatization severity was correlated with the FA values of the cingulum and inferior fronto-occipital fasciculus in the patients. The patients exhibit suggestive alterations in WM integrity in the cingulum, inferior fronto-occipital fasciculus, anterior thalamic radiation, and corticospinal tract.

Treatment Outcome-Related White Matter Differences in Veterans with Posttraumatic Stress Disorder.

Posttraumatic stress disorder (PTSD) is a debilitating disorder that has been associated with brain abnormalities, including white matter alterations. However, little is known about the effect of treatment on these brain alterations. To investigate the course of white matter alterations in PTSD, we used a longitudinal design investigating treatment effects on white matter integrity using diffusion tensor imaging (DTI). Diffusion tensor and magnetization transfer images were obtained pre- and posttreatment from veterans with (n=39) and without PTSD (n=22). After treatment, 16 PTSD patients were remitted, and 23 had persistent PTSD based on PTSD diagnosis. The dorsal and hippocampal cingulum bundle, stria terminalis, and fornix were investigated as regions of interest. Exploratory whole-brain analyses were also performed. Groups were compared with repeated-measures ANOVA for fractional anisotropy (FA), and magnetization transfer ratio. Persistently symptomatic PTSD patients had increasing FA of the dorsal cingulum over time, and at reassessment these FA values were higher than both combat controls and the remitted PTSD group. Group-by-time interactions for FA were found in the hippocampal cingulum, fornix, and stria terminalis, posterior corona radiata, and superior longitudinal fasciculus. Our results indicate that higher FA of the dorsal cingulum bundle may be an acquired feature of persistent PTSD that develops over time. Furthermore, treatment might have differential effects on the hippocampal cingulum, fornix, stria terminalis, posterior corona radiata, and superior longitudinal fasciculus in remitted vs persistent PTSD patients. This study contributes to a better understanding of the neural underpinnings of PTSD treatment outcome.

Interés del uso clínico del tensor de difusión en la planificación del tratamiento rehabilitador en pacientes tras el primer ictus

ObjectiveTo compare the predictive value of the MR diffusion tensor (DT) imaging modality in a sample of stroke patients. Material and methodA prospective study was conducted on 7 inpatient subjects of both genders who were undergoing intensive rehabilitation after a first ischemic stroke. The protocol included: 1) motor skills evaluation by Motor Index, Trunk Control Test; 2) Walking capacity: functional assessment categories and functional capacity: Barthel Index and Functional Independence Measure (FIM); 3) Tractography study: mean and standard deviation for fractional anisotropy (FA) and apparent diffusion coefficient (ADC) in internal capsule, corona radiata and right and left pontine tract; 4) Statistical analysis: projection of the data into a two-dimensional scatterplot matrix; verification of every possible link with a simple regression model (linear or logistic). Results with P-value <0.2 are included. ResultsThe relations with two pairs of variables that are significant are: 1) upper extremity motor skill and FA values in the pontine tract; 2) lower extremity motor skill and FA values at the corona radiate; 3) motor and cognitive FIM with ADC at the corona radiate; 4) motor and cognitive FIM with FA in the pontine tract; 5) Cognitive FIM and FA at the corona radiate; 6) FIM total and FA at the internal capsule and pontine tract and, 7) total FIM and ADC in the pontine tract. The results represent the preliminary findings of the use of DT in a small sample of stroke patients in a neurorehabilitation unit. We consider DT to be useful in the evolutive prediction of stroke.

Diffusion Tensor Imaging Predicts Long-Term Motor Functional Outcome in Patients with Acute Supratentorial Intracranial Hemorrhage

Background/Aim: It remains unclear how wallerian degeneration of the pyramidal tract (PT) in the acute phase of supratentorial intracranial hemorrhage (ICH) correlates with the long-term functional outcome. The aim of this study was to quantify and predict the long-term neuromotor outcome using diffusion tensor imaging (DTI) during the early stages of ICH. Methods: Twenty-seven patients with a hemiparetic ICH were prospectively studied using DTI either within 3 days or at 2 weeks after onset. A region-of-interest-based analysis was performed for fractional anisotropy (FA) of the PT in the cerebral peduncle. The degree of paresis was assessed upon admission and at 6 months using paresis grading (PG), and the functional outcome was evaluated using the modified Rankin Scale (mRS). The activities of daily living were evaluated using the Functional Independence Measure (FIM). Results: The FA values within 3 days and after 2 weeks of ICH onset were significantly decreased at the affected side (p = 0.001, reduced by 11%; p < 0.001, reduced by 14%, respectively), but the mean diffusivity at the same time points remained unchanged (p = 0.05 and p = 0.136, respectively). The ratio of the FA (rFA) at the affected side to that of the unaffected side within 3 days was negatively correlated with the PG (p < 0.001, r = –0.642), positively correlated with the FIM scores (p = 0.004, r = 0.532), and negatively correlated with the mRS scores at the end of follow-up (median = 17 months) (p = 0.010, r = –0.490). The rFA at 2 weeks was positively correlated with the FIM (p < 0.001, r = 0.661) and negatively correlated with mRS scores and PG at the end of follow-up (p < 0.001, r = –0.653; p < 0.001, r = –0.700). For both patients with good and poor outcomes based on the PG, the area under the receiver operating characteristic (ROC) curve for rFA at 2 weeks was greater than the area under the ROC for rFA within 3 days, and the cutoff point for the rFA at 2 weeks was set at 0.875 (sensitivity 76%, specificity 89%). Conclusions: This study demonstrated that the use of DTI during the early stages of ICH may predict motor outcomes at 6 months after ICH. Moreover, as compared to use of DTI within 3 days of ICH onset, the application of DTI at 2 weeks after ICH could more accurately predict the motor outcomes and daily living activities of patients.

Neuroimaging Correlates of Traumatic Brain Injury and Suicidal Behavior

There is an urgent need to define the neurobiological and cognitive underpinnings of suicidal ideation and behavior in veterans with traumatic brain injury (TBI). Separate studies implicate frontal white matter systems in the pathophysiology of TBI, suicidality, and impulsivity. We examined the relationship between the integrity of major frontal white matter (WM) systems on measures of impulsivity and suicidality in veterans with TBI. Fifteen male veterans with TBI and 17 matched healthy controls (HC) received clinical ratings, measures of impulsivity and MRI scans on a 3T magnet. Diffusion tensor imaging (DTI) data for the genu and cingulum were analyzed using Freesurfer and FSL. Correlations were performed for fractional anisotropy (FA) (DTI) values and measures of suicidality and impulsivity for veterans with TBI. Significantly decreased in FA values in the left cingulum (P = 0.02), and left (P = 0.02) and total genu (P = 0.01) were observed in the TBI group relative to controls. Measures of impulsivity were significantly greater for the TBI group and total and right cingulum FA positively correlated with current suicidal ideation and measures of impulsivity (P <0.03). These data demonstrate a significant reduction in FA in frontal WM tracts in veterans with mild TBI that was associated with both impulsivity and suicidality. These findings may reflect a neurobiological vulnerability to suicidal risk related to white matter microstructure.

Multiple DTI index analysis in normal aging, amnestic MCI and AD. Relationship with neuropsychological performance

White matter (WM) damage has been reported in Alzheimer's Disease (AD) and Mild Cognitive Impairment (MCI) in diffusion tensor imaging (DTI) studies. It is, however, unknown how the investigation of multiple tensor indexes in the same patients, can differentiate them from normal aging or relate to patients cognition. Forty-six individuals (15 healthy, 16 a-MCI and 15 AD) were included. Voxel-based tract based spatial-statistics (TBSS) was used to obtain whole-brain maps of main WM bundles for fractional anisotropy (FA), radial diffusivity (DR), axial diffusivity (DA) and mean diffusivity (MD). FA reductions were evidenced among AD patients with posterior predominance. A-MCI patients displayed reduced mean FA in these critical regions, compared to healthy elders. MD increases were widespread in both groups of patients. Interestingly, a-MCI patients exhibited DR increases in overlapping areas of FA shrinkages in AD, whereas DA increases were only observed in AD. Gray matter atrophy explained most DTI differences, except those regarding MD in both groups as well as DR increases in posterior associative pathways among a-MCI cases. FA values were the only DTI measure significantly related to memory performance among patients. Present findings suggest that most DTI-derived changes in AD and a-MCI are largely secondary to gray matter atrophy. Notably however, specific DR signal increases in posterior parts of the inferior fronto-occipital and longitudinal fasciculi may reflect early WM compromise in preclinical dementia, which is independent of atrophy. Finally, global measures of integrity, particularly orientation coherence (FA) of diffusion, appear to be more closely related to the cognitive profile of our patients than indexes reflecting water movement parallel (DA) and perpendicular (DR) to the primary diffusion direction.