Diffusion Tensor Imaging and Fiber Tractography

Objectives: We aim to investigate whether multi-dimensional diffusion tensor imaging (DTI) measures can sensitively identify different cognitive status of cerebral small vessel disease (CSVD) and to explore the underlying pattern of white matter disruption in CSVD.Methods: Two hundred and two participants were recruited, composed of 99 CSVD patients with mild cognitive impairment (VaMCI) and 60 with no cognitive impairment (NCI) and 43 healthy subjects as normal controls (NC). Full domain neuropsychological tests and diffusion-weighted imaging were performed on each subject. DTI metrics such as fractional anisotropy (FA), mean diffusivity (MD), the skeletonized mean diffusivity (PSMD), and structural brain network measures including network strength, global efficiency (EGlobal), and local efficiency (ELocal) were calculated. Region of interest (ROI) analysis of 42 white matter tracts was performed to examine the regional anatomical white matter disruption for each group.Results: Significant differences of multiple cognitive test scores across all cognitive domains especially processing and executive function existed among the three groups. DTI measures (FA, MD, and PSMD) showed significant group difference with the cognitive status changing. FA and EGlobal showed significant correlation with processing speed, executive function, and memory. ROI analysis found that white matter integrity impairment occurred from the preclinical stage of vascular cognitive impairment (VCI) due to CSVD. These lesions in the NCI group mainly involved some longitudinal fibers such as right superior longitudinal fasciculus (SLF-R), right superior fronto-occipital fasciculus (SFO-R), and right uncinate fasciculus (UNC-R), which might be more vulnerable to the cerebrovascular aging and disease process.Conclusions: DTI measures are sensitive neuroimaging markers in detecting the early cognitive impairment and able to differentiate the different cognitive status due to CSVD. Subtle changes of some vulnerable white matter tracts may be observed from the preclinical stage of VCI and have a local to general spreading pattern during the disease progression.

Primary brain tumors comprise 28% of all tumors and 80% of malignant tumors. Pathophysiology of high-grade gliomas includes significant distortion of white matter architecture, necrosis, the breakdown of the blood brain barrier, and increased intracranial pressure. Diffusion tensor imaging (DTI), a diffusion weighted imaging technique, can be used to assess white matter architecture. Use of DTI as a non-invasive pathophysiological tool to analyze glioma impact on white matter microstructure has yet to be fully explored.Preliminary assessment of DTI tractography was done as a measure of intracranial tumor impact on white matter architecture. Specifically, we addressed three questions: 1) whether glioma differentially affects local white matter structure compared to metastasis, 2) whether glioma affects tract integrity of major white matter bundles, 3) whether glioma lobe localization affects tract integrity of different white matter bundles.In this study, we retrospectively investigated preoperative DTI scans from 24 patients undergoing tumor resection. Fiber tractography was estimated using a deterministic fiber tracking algorithm in DSI (diffusion spectrum imaging) Studio. The automatic anatomical labeling (AAL) atlas was used to define the left and right (L/R) hemisphere regions of interest (ROI). In addition, the John Hopkins University (JHU) White Matter Atlas was used to auto-segment major white matter bundle ROIs. For all tracts derived from ROI seed targets, we computed the following parameters: tract number, tract length, fractional anisotropy (FA), axial diffusivity (AD), mean diffusivity (MD), and radial diffusivity (RD).The DTI tractography analysis revealed that white matter integrity in the hemisphere ipsilateral to intracranial tumor was significantly compromised compared to the control contralateral hemisphere. No differences were observed between high vs low-grade gliomas, however, gliomas induced significantly greater white matter degradation than metastases. In addition, targeted analysis of major white matter bundles important for sensory/motor function (i.e., corticospinal tract and superior longitudinal fasciculus) revealed tract-parameter specific susceptibility due to the presence of the tumor. Finally, major tract bundles were differentially affected based on lobar localization of the glioma.These DTI-based tractographic analyses complement findings from gross histopathological examination of glioma impact on neural tissue. Global and focal white matter architecture, ipsilateral to glioma, shows higher rates of degradation or edema – based on DTI tractographic metrics – in comparison to normal brain or metastases. Gliomas, which arise in the parietal lobe, also have a higher negative impact (potentially due to increased edema) on white matter integrity of the superior longitudinal fasciculus(SLF) than those which arise in the frontal lobe. Future studies will focus on using preoperative and postoperative tractography to predict functional deficits following resective surgery.

In this paper, we present a novel set of features which mainly comprises Fourier descriptors to facilitate the classification of white matter (WM) fiber tracts reconstructed from diffusion tensor imaging (DTI) tractography. Particularly, Fourier descriptors composing the feature vectors are different frequency terms of the discrete Fourier transform of the Euclidean coordinates of the step points of WM fiber tracts. This approach can effectively reduce the computing cost in WM fiber tract classification due to the decreased feature vector dimensionality. As integrals, Fourier descriptor features make the algorithm less sensitive to DTI noise. The fact that Fourier descriptors achieve spatial independent representation and normalization of WM fiber tracts makes it useful for group studies of WM fiber tracts. Specially, a new strategy for using Fourier descriptors is proposed. Experimental results with real datasets show that this technique is feasible and may be an alternative to existing approaches.

ObjectiveThis study examined the association of lifetime experiences, measured by a cognitive reserve (CR) composite score composed of years of education, literacy, and vocabulary measures, to level and rate of change in white matter microstructure, as assessed by diffusion tensor imaging (DTI) measures. We also examined whether the relationship between the proxy CR composite score and white matter microstructure was modified by participant age, APOE-ε4 genetic status, and level of vascular risk.MethodsA sample of 192 non-demented (n = 166 cognitively normal, n = 26 mild cognitive impairment) older adults [mean age = 70.17 (SD = 8.5) years] from the BIOCARD study underwent longitudinal DTI (mean follow-up = 2.5 years, max = 4.7 years). White matter microstructure was quantified by fractional anisotropy (FA) and radial diffusivity (RD) values in global white matter tracts and medial temporal lobe (MTL) white matter tracts.ResultsUsing longitudinal linear mixed effect models, we found that FA decreased over time and RD increased over time in both the global and MTL DTI composites, but the rate of change in these DTI measures was not related to level of CR. However, there were significant interactions between the CR composite score and age for global RD in the full sample, and for global FA, global RD, and MTL RD among those with normal cognition. These interactions indicated that among participants with a lower baseline age, higher CR composite scores were associated with higher FA and lower RD values, while among participants with higher age at baseline, higher CR composite scores were associated with lower FA and higher RD values. Furthermore, these relationships were not modified by APOE-ε4 genotype or level of vascular risk.ConclusionThe association between level of CR and DTI measures differs by age, suggesting a possible neuroprotective effect of CR among late middle-aged adults that shifts to a compensatory effect among older adults.

BackgroundThough previous research supports diffusion tensor imaging (DTI) as a biomarker for white matter integrity in diseases such as Alzheimer’s disease/mild cognitive impairment (ADMCI), Parkinson’s disease (PD), and cerebrovascular disease (CVD), few studies have compared white matter microstructure between different neurodegenerative aetiologies. This study aimed to characterize and compare the microstructure of white matter tracts in ADMCI, PD, and CVD patients using DTI data from the Ontario Neurodegenerative Disease Research Initiative (ONDRI).MethodThe ONDRI study included 119 ADMCI, 149 CVD, and 137 PD patients with usable DTI and T1 MRI data. FreeSurfer’s TRACULA [https://dmri.mgh.harvard.edu/tract‐atlas/] was used to reconstruct 39 white matter pathways and calculate average DTI metrics (fractional anisotropy, FA; mean diffusivity, MD; axial diffusivity, AxD; and radial diffusivity, RD) in each pathway. Patients with severe cerebral infarcts, hypointensities, or ventricular dilation that compromised tract reconstruction were excluded from further analyses. The final dataset included 96 ADMCI [n(%)female=50(52%); median(range)age=71(53‐87)], 107 CVD [n(%)female=35(33%); median(range)age=69(55‐85)], and 117 PD [n(%)female=28(24%); median(range)age=68(55‐84)] participants. Multivariate general linear models evaluated the effect of diagnosis on FA, MD, AxD, and RD in all 39 tracts.Result3D segmentations of the 39 white matter tracts in a representative subject are shown in Figure 1. In the multivariate analyses, diagnosis had a strong, significant effect on all four DTI metrics (FA: p = 0.002, ηp2=0.180; MD: p = 0.001, ηp2=0.183; AxD: p = 0.003, ηp2=0.178; RD: p = 0.002, ηp2=0.181). Figures 2 and 3 display the post hoc pairwise comparisons of FA and MD, respectively, in only the tracts for which diagnosis had a significant (p<0.05) effect in the univariate analyses. On average, PD participants had higher FA (2.3%, ηp2=0.030) and lower MD (1.7%; ηp2=0.032), AxD (1.3%; ηp2=0.036), and RD (2.3%; ηp2=0.027) within these tracts compared to ADMCI and CVD participants. There were very few significant differences between ADMCI and CVD participants.ConclusionPD participants had slightly more preserved white matter tract microstructural integrity than ADMCI or CVD participants who had lower FA and higher RD and MD values. Higher‐quality, advanced diffusion imaging may be necessary to detect the more subtle changes in white matter microstructure present in Parkinson’s disease patients.

Diffusion Tensor Imaging and Fiber Tractography in Acute Stroke

The corticoreticular pathway (CRP) mainly mediates proximal and axial muscles and therefore it is an important neural tract for walking (Miyai et al., 2002; Matsuyama et al., 2004; Mendoza and Foundas, 2007). Diffusion tensor tractography (DTT), derived from diffusion tensor imaging (DTI), enables reconstruction of the CRP three-dimensionally and several studies have reported on the association between the CRP and gait recovery (Yeo et al., 2012a, 2013; Jang et al., 2013, 2015; Jang and Seo, 2014; Kwon and Jang, 2014). However, to the best of our knowledge, there has been no report on degeneration of the CRP. In the current study, we reported on a patient with intracerebral hemorrhages (ICHs) in both hemispheres, presenting with gait deterioration due to neural degeneration of the CRP as shown on DTT images. A 64-year-old male presented with gait deterioration which started 2 months ago. He had a history of spontaneous ICHs in both putamens (the right ICH: 19 years ago, and the left ICH: 11 years ago). The patient's motor weakness was measured using Medical Research Council (MRC) scale (Council, 1976). His walking ability was assessed using Functional Ambulatory Category (FAC) (Cunha et al., 2002). Before the onset of gait deterioration, his motor function had recovered to a subnormal state in the right extremities and a nearly normal state in the left extremities; therefore, he was able to walk independently, even on stairs (FAC: 4). Since about 2 months ago, his gait function had begun to deteriorate and aggravated progressively with time. Two months after the onset of gait disturbance, he could not walk independently, even on floors (FAC: 1.5). He presented with weakness of proximal joints along with more severe weakness in the right extremities compared with the left side (MRC scale, shoulder abductor: 4-/4, elbow flexor: 4/4+, finger extensor: 4/4+, hip flexor: 4-/4, knee extensor: 4/4+, ankle dorsiflexor: 4/4+) (Council, 1976). Brain MR images taken at 2 months after onset of gait deterioration showed leukomalactic lesions in both subcortical white matter and basal ganglia (Figure 1B).Figure 1: Brain CT and MR images and results of diffusion tensor tractography (DTT) in a 64-year-old male patient with gait deterioration.(A) Brain CT images at 11 years before onset of gait deterioration show a spontaneous intracerebral hemorrhage in the left putamen (red arrows). (B) Brain MR images taken at 2 months after onset of gait deterioration showed leukomalactic lesions in both subcortical white matter and basal ganglia (yellow arrows). (C) Results of DTT. On the first DTT images (6 years before onset of gait deterioration), the integrities of the corticoreticular pathways (CRPs) in both hemispheres were preserved from the cerebral cortex to the medulla. By contrast, on the second DTT images (2 months after onset of gait deterioration), both CRPs showed discontinuations (green arrows) at the corona radiata level compared with the first DTT images. (D) DTTs of the CRP of two age and sex-matched normal control subjects (62- and 66-year-old males). The red (C) and yellow (D) mean the right and left corticoreticular pathway, respectively.DTI data were obtained twice (first DTI: 6 years ago and second DTI: 2 months after onset of gait deterioration). Sixty contiguous slices (field of view = 240 × 240 mm2; repetition time = 10,726 ms; echo time = 76 ms; b = 1,000 s/mm2; number of excitations = 1; and thickness = 2.5 mm) were acquired. FACT algorithm was used for fiber tracking. The CRP was reconstructed using fibers passing through two regions of interest (ROIs) on the color map. The first ROI was given at the medullary reticular formation and the second ROI at the midbrain tegmentum. Termination criteria used for fiber tracking were fractional anisotropy (FA) of less than 0.2 and angle of less than 60°. On the first DTT scan performed 6 years ago, the integrities of the CRPs in both hemispheres were preserved from the cerebral cortex to the medulla. By contrast, on the second DTT taken at 2 months after onset of gait deterioration, both CRPs showed discontinuation at the corona radiata level compared with the first DTT (Figure 1C). In this study, the gait deterioration in this patient was ascribed to delayed neural degeneration of both CRPs. The patient began to show gait deterioration 2 months ago, before undergoing the second DTT. The second DTT for the CRP, taken at 2 months after onset of gait deterioration, showed discontinuations at the corona radiata compared with the first DTT (6 years ago), which showed that integrities of both CRPs were intact. This finding was consistent with the characteristics of motor weakness of the patient (more severe weakness of proximal muscles) (Matsuyama et al., 2004; Mendoza and Foundas, 2007; Yeo et al., 2013). Regarding the pathophysiological mechanism of delayed neural degeneration of the CRP in the corona radiata, injury of peri-lesional white matter might occur through a chemical mechanism: a blood clot might release potentially toxic substances which can induce injury to neural tissue, such as free iron, which might release free radicals or inflammatory cytokines (Chua et al., 2009; Yeo et al., 2012b). However, other factors that can deteriorate the gait function such as normal aging or physical deconditioning should be also considered. Accompanying neural degeneration is often observed after stroke (Yu et al., 2009; Puig et al., 2010). Many studies have reported on Wallerian degeneration that started immediately after neuronal injury in the acute stage of stroke (Yu et al., 2009; Puig et al., 2010). Wallerian degeneration is a process characterized by degeneration of axons and their distal part myelin sheath in the central and peripheral nervous system. However, little is known about delayed neural degeneration in stroke patients. To the best of our knowledge, this is the first study to report on neural degeneration of the CRP although a few previous studies have reported on neural degeneration of the CST in stroke patients (Radlinska et al., 2009; Jang ans Seo, 2016). However, DTI might underestimate the neural fibers due to the fiber-crossing effect (Yamada et al., 2009), which should be considered. In conclusion, we report on a patient who showed delayed gait deterioration due to neural degeneration of the CRP. We believe that DTT evaluation of the CRP would be helpful to elucidate the mechanism behind delayed gait deterioration in stroke patients. This work was supported by the National Research Foundation (NRF) of Korea Grant funded by the Korean Government (MSIP), No. 2015R1A2A2A01004073.

The study of complex computational systems is facilitated by network maps, such as circuit diagrams. Such mapping is particularly informative when studying the brain, as the functional role that a brain area fulfills may be largely defined by its connections to other brain areas. In this report, we describe a novel, non-invasive approach for relating brain structure and function using magnetic resonance imaging (MRI). This approach, a combination of structural imaging of long-range fiber connections and functional imaging data, is illustrated in two distinct cognitive domains, visual attention and face perception. Structural imaging is performed with diffusion-weighted imaging (DWI) and fiber tractography, which track the diffusion of water molecules along white-matter fiber tracts in the brain (Figure 1). By visualizing these fiber tracts, we are able to investigate the long-range connective architecture of the brain. The results compare favorably with one of the most widely-used techniques in DWI, diffusion tensor imaging (DTI). DTI is unable to resolve complex configurations of fiber tracts, limiting its utility for constructing detailed, anatomically-informed models of brain function. In contrast, our analyses reproduce known neuroanatomy with precision and accuracy. This advantage is partly due to data acquisition procedures: while many DTI protocols measure diffusion in a small number of directions (e.g., 6 or 12), we employ a diffusion spectrum imaging (DSI)(1, 2) protocol which assesses diffusion in 257 directions and at a range of magnetic gradient strengths. Moreover, DSI data allow us to use more sophisticated methods for reconstructing acquired data. In two experiments (visual attention and face perception), tractography reveals that co-active areas of the human brain are anatomically connected, supporting extant hypotheses that they form functional networks. DWI allows us to create a "circuit diagram" and reproduce it on an individual-subject basis, for the purpose of monitoring task-relevant brain activity in networks of interest.

Summary: The use of Diffusion Tensor Imaging (DTI) tractography has exploded over the past two decades, proving to be a major advancement in the current methods for exploring the architecture of white matter tracts in the living human brain. Despite making up 50% of brain tissue, investigations into the function of white matter have long remained in the background of medical research. Consequently, white matter pathology cited in neuropsychiatric disease remains a heavy burden of human illness. Nonetheless, with novel diffusion MRI techniques, including DTI tractography, we are able to visualise areas of the brain better than ever before, furthering our understanding of white matter beyond the crude depictions offered by conventional MRI. Relevance: It is important that medical students have an understanding of DTI tractography because it has the potential to illuminate mechanisms that underpin cognition and emotion through the creation of connectional maps. Furthermore, advances in MR technology should not be restricted to the territory of academics. Instead, both medical students and clinicians should be able to draw upon the current research methods to improve the care and understanding of patients with white matter pathology. Take Home Messages: 1. Diffusion Tensor Imaging is a diffusion MRI technique that depicts the movement of water molecules along major white matter pathways in the living brain. 2. Using information from DTI, tractography software virtually reconstructs white matter tracts and can be used to make dissections of major fasciculi in vivo. 3. DTI tractography remains the only non-invasive method to study white matter tracts in the living human brain. 4. Results from tractography are increasingly being used in neuropsychiatric research. 5. Despite its potential, DTI tractography still faces a number of challenges. The most prominent of these being its inability to accurately map crossing fibres within a voxel.

Lithium is the mainstay for the treatment of bipolar disorder (BD) and inhibits glycogen synthase kinase 3-β (GSK3-β). The less active GSK3-β promoter gene variants have been associated with less detrimental clinical features of BD. GSK3-β gene variants and lithium can influence brain gray matter structure in psychiatric conditions. Diffusion tensor imaging (DTI) measures of white matter (WM) integrity showed widespred disruption of WM structure in BD. In a sample of 70 patients affected by a major depressive episode in course of BD, we investigated the effect of ongoing long-term lithium treatment and GSK3-β promoter rs334558 polymorphism on WM microstructure, using DTI and tract-based spatial statistics with threshold-free cluster enhancement. We report that the less active GSK3-β rs334558*C gene-promoter variants, and the long-term administration of the GSK3-β inhibitor lithium, were associated with increases of DTI measures of axial diffusivity (AD) in several WM fiber tracts, including corpus callosum, forceps major, anterior and posterior cingulum bundle (bilaterally including its hippocampal part), left superior and inferior longitudinal fasciculus, left inferior fronto-occipital fasciculus, left posterior thalamic radiation, bilateral superior and posterior corona radiata, and bilateral corticospinal tract. AD reflects the integrity of axons and myelin sheaths. We suggest that GSK3-β inhibition and lithium could counteract the detrimental influences of BD on WM structure, with specific benefits resulting from effects on specific WM tracts contributing to the functional integrity of the brain and involving interhemispheric, limbic, and large frontal, parietal, and fronto-occipital connections.

Introduction We present the first study in literature that documents the changes in diffusion tensor imaging (DTI) indices and tractography after surgical decompression in patients with cervical myelopathy. DTI, an established tool for tracking nerve fibers in brain, is now widely evaluated for its usefulness in spine pathologies. Although there are many studies directly comparing DTI indices of control and cervical myelopathic patients, there are no studies that have evaluated the prognostic applicability of DTI indices. The present study analyzes the pre- and postdecompression DTI indices and tractography in cervical myelopathic patients and its prognostic value. Materials and Methods Total 56 subjects including 16 cervical myelopathy patients who required surgical decompression (mean age: 53.5 ± 12.3 years, males: 15, females: (1) and forty normal controls (mean age: 38.18 ± 13.74 years, males: 20, females: 20) were included in the study. DTI of cervical spine was obtained using an axial single shot echo-planar parallel diffusion-weighted imaging sequence in a 1.5 tesla magnetic resonance imaging (MRI). Apparent diffusion coefficient (ADC), fractional anisotropy (FA), and Eigen values (E1, E2, and E3) were obtained at each region of interest (cervical disk level) from C1-C2 to C7-T1. The DTI indices of myelopathic patients were compared with normal volunteers after matching was done based on sex, cord level, and cord size. Postoperatively, the patients were followed up after 6 months and DTI scan was performed again. The clinical improvement and the DTI indices observed at the follow-up were compared with the preoperative values. Results Analysis showed significant differences between the controls and patients in all the indices (p&lt;0.05) at the site of compression. At the compressed levels, FA decreased while all the other indices increased as compared to the controls. The mean DTI indices of myelopathic patients before surgery at the sites of spinal cord compression were as follows: FA (0.49 ± 0.092), ADC (1.8 ± 0.32 µm2/ms), E1 (2.80 ± 0.44 µm2/ms), E2 (1.63 ± 0.45 µm2/ms), E3 (0.95 ± 0.23 µm2/ms). The average DTI indices of matched controls were as follows: FA (0.55 ± 0.033), ADC (1.47 ± 0.066 µm2/ms), E1 (2.49 ± 0.150 µm2/ms), E2 (1.16 ± 0.050 µm2/ms), E3 (0.77 ± 0.058 µm2/ms. The Nurick grading distribution in patients before surgery was as follows: Grade 2 = 2, Gr 3 = 8, Gr 4 = 2, Gr 5 = 4. Postoperatively, all the patients had improvement of neurology by at least one Nurick grade except for one patient who had no improvement. The Nurick grading distribution in patients during 6 months follow-up after surgery was as follows: Grade 0 = 3, Gr 1 = 6, Gr 2 = 2, Gr 3 = 3, Gr 4 = 2. Mean postoperative values of ADC, E1, and E2 showed improvement towards normal values especially in patients with preoperative Nurick grade 2 and 3 (Table 1). Patients with Nurick grade 4 and 5 did not show any significant change. The mean FA and E3 values worsened when compared to preoperative DTI indices. The postoperative DTI indices for the patients who had neurological improvement are as follows: FA (0.45 ± 0.087), ADC (1.73 ± 0.31 µm2/ms), E1 (2.59 ± 0.28 µm2/ms), E2 (1.56 ± 0.38 µm2/ms), E3 (1.07 ± 0.31 µm2/ms. Tractography also showed interruption of nerve fibre tract continuity at the level of severe compression in patients with myelopathy. At levels of moderate compression over the spinal cord, the changes in direction of nerve fibres due to bulging disc-osteophytes were evident as changes in color coding of the tracts. After surgical decompression, the restitution of fibre tract pathways was clearly demonstrated in DT tractography. Conclusion For the first time, the prognostic applicability of DTI by comparing pre- and postoperative indices of cervical myelopathy patients has been described. All preoperative DTI indices at compressed levels showed significant differences from controls indicating abnormality in neuronal integrity. All but one of the patients showed clinical improvement at 6 months. The postoperative DTI values (ADC, E1 and E2) of patients with Nurick grading 2 and 3 were observed to approach normal values indicating restoration of linear diffusion in neuronal tracts. DTI indices in patients with Nurick grade 4 and 5 remained same or worsened more. This could probably indicate persistent axonal damage. At 6 months postsurgery, DTI indices show evidence of improvement towards normal values, even though the values did not match the true extent of clinical improvement. Further DTI evaluation at 12 months and 2 years is required to analyze the extent of usefulness of DTI indices in evaluating cervical myelopathy. The results suggest that DTI indices, especially ADC and Eigen vectors can be promising indicators in the evaluation and prognostic assessment of myelopathy patients. I confirm having declared any potential conflict of interest for all authors listed on this abstract Yes Disclosure of Interest None declared

<h3>Background</h3> Recent diffusion tensor imaging (DTI) studies suggest that abnormalities in Huntington9s disease (HD) extend to white matter (WM) tracts in early HD and even in presymptomatic (PreHD) stages. However, DTI tractography, which allows precise localisation of WM abnormalities has not yet been used to investigate changes associated with HD. <h3>Aims</h3> The purpose of this study was to investigate whether the corpus callosum (CC) of PreHD subjects exhibit a measurable difference compared to healthy controls and HD patients in the Forceps Major (posterior projections) and Minor (frontal projections). <h3>Methods</h3> All T1 and DTI data were acquired on a 3T Allegra MRI system (Siemens) for 33 healthy controls (22M/11F; age: 43.88±11.69), 19 PreHD subjects (13M/6F; age: 38.11±7.75) and 23 HD patients (13M/10F; age: 48.30±13.79). DTI scans were acquired with 30 directions and three acquisitions. The Forceps Major and Minor were delineated using predefined ROI9s in TrackVis. The general linear model was used to compare tract volume with sex, age and CC volume included in the model. <h3>Results</h3> Mean track volume for the FMajor: Controls=18.28±5.07, PreHD= 15.23±4.16, HD=13.98±4.16, and FMinor: Controls=14.90±4.21, PreHD=16.18±4.12, HD=11.60±4.08). Controls had a significantly larger FMajor compared to PreHD F[1,51]=6.534, p&lt;0.02 and PreHD subjects had a significantly larger FMajor compared to HD patients F[1,42]=4.44, p &lt;0.045. PreHD subjects had a significantly larger FMinor than HD Patients F[1,42]=13.261, p&lt;002. <h3>Conclusion</h3> The results suggest there is a significant difference in posterior and frontal CC projections between PreHD subjects and HD patients indicating a volume reduction associated with disease progression. Furthermore, PreHD subjects exhibit significantly smaller posterior projections compared to healthy controls but no significant difference in frontal projections, signalling a posterior-to-anterior direction in disease progression.

Objective Astrocytic tumors in motor area often grow infihratively with worse outcome. It is significant to identify the tumor infiltrating field before the operation to improve the outcome of surgery. Diffusion tensor imaging(DTI) is an advanced quantitative form of diffusion-weighted imaging. The study is to discuss the clinical application of DTI in identifying, forecasting the grades of astrocytoma and choosing the best procedure for resecting astrocytoma. Method The clinical data of consecutive 33 patients with astrocytoma in motor function area underwent DTI examination before the operation. Results Compared with normal brain tissue, significant differences of ADC and FA were found in solid area of astrocytoma necrotic region, edema region(P<0.05). Significant differences of ADC were also found in solid tumor compared with necrotic region and edema region respectively(P<0.05). By the imaging guidance of DTI, we could show white matter fiber tracts of the motor area and evaluate the relationship between astrocytoma and white matter fiber for the operation. Conclusions ADC and FA can be used to differentiate normal brain tissue from astrocytoma. According to the change of white matter fiber tracts around the tumors in DTT, we could optimize the operational project and improve the resection of astrocytoma significantly, as well as to decrease potential disability after operation. Key words: Astrocytoma; Diffusion magnetic resonance imaging

Abnormal frontal cortex white matter connections in bipolar disorder: A DTI tractography study

Magnetic resonance imaging (MRI) diffusion tensor imaging (DTI) measures have been described as methods for quantifying spinal cord injury and predicting outcome in dogs with intervertebral disc herniation (IVDH); however, studies comparing methods for selecting regions of interest (ROIs) are currently lacking. The aims of this retrospective, methods comparison, observational study were to compare DTI measurements acquired using manual (mROI) versus semiautomated ROI (sROI) methods and to compare DTI measurements with patient outcomes. Magnetic resonance imaging scans that included DTI pulse sequences were retrieved for 65 dogs with confirmed IVDH. Regions of interest were placed at one vertebral length cranial and caudal to the region of spinal cord compression (RSCC) using the mROI and sROI methods. Scalar values based on the mROI and sROI methods were compared. There was a significant difference for all DTI measures (P<0.0001), where fractional anisotropy was higher (95% confidence interval [CI]: 0.15, 0.19) and mean diffusivity (MD; CI: -0.41, -0.35), axial diffusivity (AD; CI: -0.47, -0.36) and radial diffusivity (RD; CI: -0.36, -0.27) were lower for the mROI than for the sROI. For both the mROI and sROI, MD, AD, and RD were significantly lower (p<0.05) at the RSCC in paraplegic dogs that did not regain motor function. The findings indicated that DTI methods for quantifying SCI using open source software and ROI were feasible for use in dogs with IVDH; however, values based on sROI methods differed from values based on mROI methods. Some DTI measures based on both the mROI and sROI methods were predictive of poor patient outcome.