Use Of Diffusion Tensor Imaging Research Articles

The use of diffusion-tensor imaging to assess microstructural integrity of white matter of patients with Alzheimer’s disease

Objective. To compare diffusion-tensor imaging (DTI) measures in different anatomic regions of the brain in patients with an isolated Alzheimer's disease (AD) and patients with AD and small-vessel disease (SVD).Material and methods. 20 AD patients, aged 66 (±10), of whom 11 AD patients had an isolated neurodegenerative process and 9 patients, who were diagnosed with AD+SVD, were examined. A research was made on a 3 T Siemens Magnetom Skyra MR-scanner. All participants underwent the same imaging protocol, which included standard clinical- and diffusion tensor pulse sequences. With an MR-image processing software package Olea Medical Sphere 3.0, fractional anisotropy (FA), mean diffusivity (MD), axial and radial diffusivity (AxD and RxD) were measured in different brain regions.Results. Significant differences in DTI measures (FA, MD, AxD, RxD), indicating more severe white matter microstructural damage in AD+SVD patients, compared with patients with an isolated AD, were observed in middle thalamic radiation, upper and lower longitudinal bundles, posterior part of cingulate gyrus and genu of corpus callosum.Conclusion. DTI is an informative method, highly sensitive in detecting difference in white matter microstructural integrity of brain tissue in individuals with an isolated AD and patients with AD+SVD.

DTI-Based Neuronavigation Guided Eloquent Area Glioma Resection with Awake Craniotomy: Supra-Functional Resection of Eloquent Area Gliomas.

To present an overview of our awake craniotomy practices performed with complementary use of diffusion tensor imaging (DTI)-based neuronavigation (DTI-bN) and cortical-subcortical electrical stimulation for glioma resection located in eloquent areas, and the clinical outcomes of these practices regarding neurological morbidity and residual tumour volume. This study was conducted between October 2016 and December 2017 involving 18 cases. The DTIbN method, in addition to cortical-subcortical stimulation, was done with awake craniotomy. Changes in the neurological status of the patients and results of the method regarding residual tumour volume were recorded. This retrospective study use data obtained from patients' records and radiological examinations. Of the 18 patients, a gross total resection was performed on nine patients (50%), a near total resection was performed on seven patients (38.8%) and a subtotal resection was performed on two patients (11.1%). Intraoperative neurological deterioration was observed in 14 of 18 patients during their surgical procedures, and neurological examinations in the sixth post-operative month revealed permanent deficits in two patients. This study is one of the rare series to have presented the results of the use DTI-bN method as well as corticalsubcortical stimulation during awake craniotomy, according to literature review. In 88% of cases, tumour resection rates are over 90%.

The longitudinal decline of white matter microstructural integrity in behavioral variant frontotemporal dementia and its association with executive function

The longitudinal decline in the integrity of several white matter (WM) tracts in behavioral variant frontotemporal dementia (bvFTD) has been documented. However, there is yet a clear relationship between this decline and that of executive function (EF), for the WM changes to meaningfully track progression in bvFTD. We sought to validate the use of diffusion tensor imaging (DTI) in tracking the progression of bvFTD with its associated decline in EF. Baseline and 1-year follow-up DTI scans were acquired from 23 patients with bvFTD and 26 healthy controls. EF composite score was derived via multiple tests. The longitudinal changes in DTI metrics were examined in both groups. Then, among patients (N = 18), we examined the associations between these changes and that of EF. Widespread WM alterations and decline in EF were observed only in patients. This EF decline was mostly associated with the disrupted integrity of the corpus callosum and anterior corona radiata. These longitudinal findings support the use of DTI in tracking the progression of bvFTD and its associated EF decline.

Diagnostic utility of central damage determination in glaucoma by magnetic resonance imaging: An observational study.

The aim of the present study was to investigate the utility of diffusion tensor imaging (DTI) parameters of the central visual pathway and the size of the lateral geniculate nucleus (LGN) in the diagnosis of primary open-angle glaucoma (POAG). To test this, 24 POAG patients and 24 age- and gender-matched controls underwent 3.0 Tesla magnetic resonance imaging examinations, including DTI and LGN structural imaging. Receiver operating characteristic (ROC) curves were generated and Spearman's correlation coefficients were also determined. The results indicated that regarding the discrimination of POAG patients from healthy controls, the fractional anisotropy (FA) values of the optic tract, at a cutoff of ≤0.412, with an area under the ROC curve of 0.931, exhibited the highest sensitivity (79.2%) and specificity (89.6%). The FA values of the optic tract and the optic radiation were significantly correlated with LGN size, while the mean diffusivity values were not. In conclusion, the FA value of the optic tract may be a sensitive and reliable biomarker for glaucoma evaluation.

Endometrial carcinoma: Evaluation using diffusion-tensor imaging and its correlation with histopathologic findings.

Although the prognosis of endometrial carcinoma (EMC) patients strictly depends on tumor invasion depth and its histologic grade, accurate preoperative assessment of these prognostic factors is often difficult. To determine the usefulness of diffusion-tensor imaging (DTI) as a noninvasive method for evaluating tumor invasion depth and its histologic grade in patients with EMC. Prospective. Twenty-five consecutive patients with histologically confirmed EMC who were surgically treated at our institution. DTI was performed with a 1.5T MRI system using a single-shot echo-planar imaging sequence with b values of 0 and 1000 s/mm2 and motion-probing gradients in nine noncollinear directions. Fractional anisotropy (FA), mean diffusivity (MD), and axial diffusivity (AD) maps were analyzed by three observers and compared with histopathologic findings. Dunnett's test, Spearman's rank correlation coefficient, and receiver operating characteristic (ROC) curve analyses. FA maps from all patients distinctly identified the junctional zone as a high-FA zone (0.864 ± 0.037) that was significantly different from the endometrium and outer myometrium (0.251 ± 0.030 and 0.471 ± 0.091, respectively; P < 0.001). All EMCs were clearly depicted as hypointense areas on all DTI maps. AD maps provided the best tumor-to-uterus contrast, and EMCs (0.977 ± 0.120 × 10-3 mm2 /s) had significantly lower AD values than all other layers of the normal uterine wall (2.166 ± 0.408, 2.010 ± 0.289, and 2.655 ± 0.203 × 10-3 mm2 /s, respectively; P < 0.001). EMCs were clearly demarcated from the normal uterine wall, and DTI maps and histopathologic data yielded identical findings regarding tumor invasion depth. FA values showed a significant inverse correlation (r = -0.818; P < 0.001) with histologic grades 1, 2, and 3 of endometrioid adenocarcinomas. In patients with EMC, DTI may be useful for evaluating tumor invasion depth and its histologic grade. 1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;50:250-260.

Nucleus Basalis of Meynert Stimulation for Dementia: Theoretical and Technical Considerations.

Deep brain stimulation (DBS) of nucleus basalis of Meynert (NBM) is currently being evaluated as a potential therapy to improve memory and overall cognitive function in dementia. Although, the animal literature has demonstrated robust improvement in cognitive functions, phase 1 trial results in humans have not been as clear-cut. We hypothesize that this may reflect differences in electrode location within the NBM, type and timing of stimulation, and the lack of a biomarker for determining the stimulation’s effectiveness in real time. In this article, we propose a methodology to address these issues in an effort to effectively interface with this powerful cognitive nucleus for the treatment of dementia. Specifically, we propose the use of diffusion tensor imaging to identify the nucleus and its tracts, quantitative electroencephalography (QEEG) to identify the physiologic response to stimulation during programming, and investigation of stimulation parameters that incorporate the phase locking and cross frequency coupling of gamma and slower oscillations characteristic of the NBM’s innate physiology. We propose that modulating the baseline gamma burst stimulation frequency, specifically with a slower rhythm such as theta or delta will pose more effective coupling between NBM and different cortical regions involved in many learning processes.

Assessment of quantitative magnetic resonance imaging metrics in the brain through the use of a novel phantom

ABSTRACTObjective: Multisite and longitudinal neuroimaging studies are important in uncovering trajectories of recovery and neurodegeneration following traumatic brain injury (TBI) and concussion through the use of diffusion tensor imaging (DTI) and other imaging modalities. This study assessed differences in anisotropic diffusion measurement across four scanners using a human and a novel phantom developed in conjunction with the Chronic Effects of Neurotrauma Consortium.Method: Human scans provided measurement within biological tissue, and the novel physical phantom provided measures of anisotropic intra-tubular diffusion to serve as a model for intra-axonal water diffusion. Intra- and inter-scanner measurement variances were compared, and the impact on effect size was calculated.Results: Intra-scanner test–retest reliability estimates for fractional anisotropy (FA) demonstrated relative stability over testing intervals. The human tissue and phantom showed similar FA ranges, high linearity and large within-device effect sizes. However, inter-scanner measures of FA indicated substantial differences, some of which exceeded typical DTI effect sizes in mild TBI.Conclusion: The diffusion phantom may be used to better elucidate inter-scanner variability in DTI-based measurement and provides an opportunity to better calibrate results obtained from scanners used in multisite and longitudinal studies. Novel solutions are being evaluated to understand and potentially overcome these differences.

The Longitudinal Decline of White Matter Microstructural Integrity in Behavioral Variant Frontotemporal Dementia and Its Association with Executive Function

Background: Previous longitudinal research has observed a decline in the integrity of several white matter (WM) tracts in behavioral variant frontotemporal dementia (bvFTD). However, without a clear relationship between these WM changes and observable behavioral changes, such as the decline in executive function (EF), it is unclear how these WM changes meaningfully reflect progression in bvFTD. The current study sought to validate the use of diffusion tensor imaging (DTI) in tracking the progression of bvFTD with its associated decline in EF. Methods: DTI scans were acquired at baseline and one-year follow-up from 23 patients with bvFTD and 26 healthy controls from the FTLDNI dataset. EF composite scores were derived multiple EF tests via confirmatory factor analysis on the larger FTLDNI dataset. The longitudinal changes in fractional anisotropy (FA) and mean diffusivity (MD) were examined via tract-based spatial statistics, separately, in both groups. FA and MD changes across time in bvFTD were regressed on EF changes. Results: Widespread clusters of significant FA decrease and MD increase, and a significant decline in EF scores were observed in patients with bvFTD, but not healthy controls. This EF decline was mostly associated with FA decrease and MD increase in the corpus callosum and anterior corona radiata. Conclusions: The bvFTD-associated decline of WM integrity was observed in several tracts, of which some were specific to EF decline. The current study presented valuable longitudinal evidence to support the use of DTI in tracking the progression of bvFTD and its associated EF decline. Funding Statement: This work is supported by funding from The University of Hong Kong May Endowed Professorship and the KKHo International Charitable Foundation. Data collection and sharing for this project was funded by the Frontotemporal Lobar Degeneration Neuroimaging Initiative (National Institutes of Health Grant R01 AG032306). The funders had no involvement in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. Declaration of Interests: The authors report no conflicts of interest. Ethics Approval Statement: Ethics approval for the FTLDNI protocol have been granted by institutional review boards at their respective study sites. (Participants with FTDs underwent comprehensive neurological, neuropsychological and functional assessment, including informant interview at one of three study sites — University of California, San Francisco, Mayo Clinic, Rochester and Massachusetts General Hospital.) The FTLDNI is coordinated through the University of California, San Francisco, Memory and Aging Center. FTLDNI data are disseminated by the Laboratory for Neuro Imaging at the University of Southern California.

P.064 Preoperative mapping using fMRI and DTI: a multimodal approach to assessing language dominance

Background: Language mapping is a key goal in neurosurgical planning. With the discontinuation of the Wada test in Canada, neurosurgeons often rely on fMRI and intraoperative techniques for determining language lateralization. Recent studies have also evaluated the utility of diffusion tensor imaging (DTI) for preoperative language lateralization, but further research is needed to confirm its efficacy. We report a patient with a left frontal AVM. fMRI and DTI was used to localize language and motor functioning. Methods: The tasks included word reading, picture naming, pseudohomophones (e.g., dawg) and semantic questions. All fMRI analyses were performed using BrainVoyager. Tensors were tracked from 30-direction diffusion MR images using DSI-Studio. Results: The fMRI results revealed consistent Broca’s and Wernicke’s areas, confirming left hemisphere dominance. There was also a region of activation in the precentral gyrus near the surgical resection. The results were loaded onto the neuronavigation system to help determine safe surgical margins. The DTI results revealed that the left arcuate and uncinate -fasciculus had three times more tracts than the right hemisphere, further supporting left hemisphere dominance. Conclusions: This case highlights the value of a combined, multimodal approach for preoperative language localization, which will further enhance surgical safety by helping preserve regions for essential brain functions.

Correlation of diffusion tensor imaging findings and episodic memory impairment in temporal lobe epilepsy

PurposeOur aim was to evaluate the utility of diffusion tensor imaging (DTI) in exploration of white matter tracts microstructure changes and clarify their relation to episodic memory in temporal lobe epilepsy (TLE). Materials and methodsDTI was performed on 30 (18 left, 12 right) TLE patients and 20 healthy controls. Fractional anisotropy (FA) and apparent diffusion coefficient (ADC) were calculated for six fiber tracts; the parahippocampal cingulum (PHC), superior longitudinal fasciculus (SLF), inferior longitudinal fasciculus (ILF), fornix (FORX), uncinate fasciculus (UF) and corpus callosum (CC). Assessment for episodic memory (visual and verbal) was performed at least 48 h after the last seizure. ResultsAll TLE patients had episodic memory impairment. Left TLE patients demonstrated more verbal memory affection, whereas right TLE patients demonstrated more visual memory affection (p < 0.05). Abnormal DTI parameters (decreased FA and increased ADC) were detected in most of the white matter tracts (p < 0.001) compared to control group. In left TLE patients, there was significant correlation between DTI parameters of left (PHC, SLF, UF, FORX) and verbal memory. Whereas, in right TLE patient, we found significant correlation between DTI parameters of right ILF and visual memory. ConclusionsTLE patients had multiple micro-structural white matter tracts abnormalities and episodic memory impairment. Both are structurally and functionally related.

Longitudinal Diffusion Tensor Imaging Resembles Patterns of Pathology Progression in Behavioral Variant Frontotemporal Dementia (bvFTD).

Objective: Recently, the characteristic longitudinal distribution pattern of the underlying phosphorylated TDP-43 (pTDP-43) pathology in the behavioral variant of frontotemporal dementia (bvFTD) excluding Pick's disease (PiD) across specific brain regions was described. The aim of the present study was to investigate whether in vivo investigations of bvFTD patients by use of diffusion tensor imaging (DTI) were consistent with these proposed patterns of progression.Methods: Sixty-two bvFTD patients and 47 controls underwent DTI in a multicenter study design. Of these, 49 bvFTD patients and 34 controls had a follow-up scan after ~12 months. Cross-sectional and longitudinal alterations were assessed by a two-fold analysis, i.e., voxelwise comparison of fractional anisotropy (FA) maps and a tract of interest-based (TOI) approach, which identifies tract structures that could be assigned to brain regions associated with disease progression.Results: Whole brain-based spatial statistics showed white matter alterations predominantly in the frontal lobes cross-sectionally and longitudinally. The TOIs of bvFTD neuroimaging stages 1 and 2 (uncinate fascicle—bvFTD pattern I; corticostriatal pathway—bvFTD pattern II) showed highly significant differences between bvFTD patients and controls. The corticospinal tract-associated TOI (bvFTD pattern III) did not differ between groups, whereas the differences in the optic radiation (bvFTD pattern IV) reached significance. The findings in the corticospinal tract were due to a “dichotomous” behavior of FA changes there.Conclusion: Longitudinal TOI analysis demonstrated a pattern of white matter pathways alterations consistent with patterns of pTDP-43 pathology.

Diffusion Tensor Imaging of Scarring, Necrosis, and Cavitation Based on Histopathological Findings in Dogs with Chronic Spinal Cord Injury: Evaluation of Multiple Diffusion Parameters and Their Correlations with Histopathological Findings.

The use of diffusion tensor imaging (DTI) for the characterization of various lesion types in dogs with spinal cord injury (SCI) has not been investigated. The aim of this study was to characterize scarring (loose immature scarring [LIMS], intermediate mature scarring [IMS], and dense mature scarring [DMS]), necrosis, cavitation, and acute hemorrhage using multiple DTI parameters and determine the correlations between the DTI parameters and histopathological finding in dogs with controlled SCI. All imaging data were obtained from the lumbar spinal cord (from L1 to L3) of normal and SCI dogs using a 3-Tesla magnetic resonance imaging scanner. Transverse multi-shot echo planar imaging (EPI) sequences (12 directions; b-value, 0 and 800 s/mm2) were used for DTI. Regions of interest on DTI maps were selected according to the areas of normal white matter (NWM), normal gray matter (NGM), LIMS, IMS, DMS, necrosis, and cavitation on histopathological images and the area of acute hemorrhage with a hypointense signal on T2*-weighted images obtained 24 h post-SCI. There were statistically significant differences in DTI parameters among NWM, NGM, multi-grade scarring, necrosis, and cavitation and between mature scarring and acute hemorrhage. The maturation grade of scarring demonstrated a positive linear correlation with fractional anisotropy and the planar index and a negative linear correlation with the spherical index and the radial, mean, and axial diffusivities. These results suggest the feasibility of using DTI for detailed noninvasive monitoring of SCI. DTI can provide critical information for guiding therapeutic strategies and determining the prognosis of SCI patients.

Anatomical Wiring and Functional Networking Changes in the Visual System Following Optic Neuritis

Clinical outcome in multiple sclerosis was suggested to be driven by not only remyelination but also adaptive reorganization. This mechanism needs to be further understood. To explore anatomical and functional visual networks in patients with optic neuritis (ON) to assess the relative weight of each connectivity modality to expedite visual recovery. Between March 11, 2011, and May 26, 2014, 39 patients with either clinically isolated syndrome (CIS) ON (n = 18) or other CIS (non-ON) (n = 21) were recruited 1 to 28 months following an initial clinical event. These patients enrolled in an ongoing prospective cohort study (107 participants at the time of this present study) about the disease course of CIS and multiple sclerosis. Inclusion criteria were an age of 18 to 65 years, the suggestive clinical and paraclinical diagnosis of CIS or multiple sclerosis after relevant differential diagnoses have been ruled out, the existence of complete imaging data, and no ocular comorbidities. Anatomical connectivity was evaluated by diffusion tensor imaging, and functional connectivity was evaluated by resting-state functional magnetic resonance imaging. The visual pathways, including optic tracts, optic radiations, and splenial fibers, were delineated, and the resting-state visual networks were detected. Data analysis took place from September 1, 2015, to December 1, 2015. Connectivity changes were quantified and compared to determine the association of ON with the visual network. This study included 18 patients with CIS ON, 11 (61%) of whom were women with a mean (SD) age of 32.83 (8.53) years, and 21 patients with CIS non-ON (11 [52%] of whom were women with a mean [SD] age of 30.86 [7.54] years). With the use of diffusion tensor imaging, reduced diffusivity (mean [SD] fractional anisotropy, 0.35 [0.03] vs 0.38 [0.03]; P < .01) was evident along the optic tracts of patients with ON, suggesting the extension of axonal injury from the damaged optic nerve. Neither the optic radiations nor the splenial fibers showed evidence of loss of integrity. Yet, in the presence of an intact postgeniculate anatomical network, the functional connectivity within the visual network was higher in the ON cohort. Functional connectivity observed in cortical motion-related areas was inversely correlated with the visual evoked potential-measured conduction velocity (r = -0.59; P < .05). In this cohort, local optic nerve demyelinating damage does not affect distant wiring, but even in the presence of an intact anatomical network, functional modification may occur. These functional network changes may be part of the recovery process, but further research is needed to elucidate this process.

Relative fractional anisotropy value using DTI: Can it help as a prognostic tool in anticipating the recovery of stroke patients?

ObjectiveTo evaluate the use of diffusion tensor imaging (DTI) and fractional anisotropy (FA) as prognostic tools in anticipating the recovery of stroke patients. Patients and methods40 patients were included in our study after exclusion of 23 patients. All patients admitted in Neurology Department with stroke. The patients subjected to National Institute of Health Stroke Scale (NIHSS) followed by MRI with DTI and FA calculation. Follow up after three months was done based on the Modified Rankin Score (MRS). The results were compared and statistically analyzed. ResultsThere was a statistical significant between the NIHSS and DTI pattern at the time of admission (p value < 0.05) reflecting the severity of the stroke with 22 patients showed disrupted fibers (55%), of which 16 patients were categorized as moderate NIHSS and 19 patients showed poor outcome. Relative FA equal 0.8 was found to be the cut off value in predicting the poor or good prognosis using MRS as a reference with 94.4% sensitivity, 90.9% specificity and 0.833 area under curve. ConclusionDTI is a prognostic tool in anticipating the recovery of the stroke patients. Moreover, the relative FA score works as more additive value in evaluation of the patient improvement.

Clinical improvement associated with targeted interruption of the cerebellothalamic tract following MR-guided focused ultrasound for essential tremor.

OBJECTIVE The objective of this study was to evaluate the utility of diffusion tensor imaging (DTI) tractography-based targeting of the dentatorubrothalamic tract (DRT) for magnetic resonance-guided focused ultrasound (MRgFUS) thalamotomy in patients with essential tremor (ET) and correlate postprocedural tract disruption with clinical outcomes. METHODS Four patients received preprocedural and immediate postprocedural DTI in addition to traditional anatomical MRI sequences for MRgFUS thalamotomy. Optimal ablation sites were selected based on the patient-specific location of the DRT as demonstrated by DTI (direct targeting) and correlated with traditional atlas-based measurements for thalamic ventral intermediate nucleus (Vim) lesioning (indirect targeting). Fiber tracts were displayed three-dimensionally during the procedure and used in conjunction with clinical signs of tremor control for fine correction of the ablation site. Immediately following the conclusion of the procedure, the MRgFUS head frame was removed and patients were placed in a 32-channel MRI head coil for follow-up DTI and anatomical MRI sequences. RESULTS All patients had excellent postoperative tremor control and successful pre- and postprocedural DTI fiber tracking of the corticospinal tract, medial lemniscus, and DRT. Immediate postprocedure DTI failed to track the DRT ipsilateral to the lesion site with a preserved contralateral DRT, coincident with substantial resolution of contralateral tremor. CONCLUSIONS DTI can reliably identify the optimal ablation target and demonstrates tract disruption on immediate postprocedural imaging. A clinical improvement of ET was observed immediately following the procedure, correlating with DRT disruption and suggesting that interruption of the DRT is a consequence of clinically successful MRgFUS thalamotomy. These findings may have utility for both MRgFUS procedure planning in surgically naive patients and retreatment of patients who have previously undergone unsuccessful thalamic Vim lesioning.

Diffusion tensor tractography in cerebral small vessel disease: correlation with cognitive function.

Background Patients with cerebral small vessel disease may suffer from varying levels of cognitive deficit and may progress on to vascular dementia. The extent of involvement, as seen on conventional magnetic resonance (MR) measures, correlates poorly with the level of cognitive decline. The purpose of this study was to investigate the utility of diffusion tensor imaging (DTI) as a marker for white matter damage in small vessel disease and to assess its correlation with cognitive function. Methods Thirty consecutive patients with cerebral small vessel disease underwent conventional MR imaging, DTI, and neuropsychological assessment. Results On tractographic analysis, fractional anisotropy was significantly reduced while mean diffusivity significantly increased in several white matter tracts. The alteration in DTI indices correlated well with cognitive function. No significant correlation was identified between T2 lesion load and cognitive performance. Conclusions Tractographic analysis of white matter integrity is a useful measure of disease severity and correlates well with cognitive function. It may have a significant potential in monitoring disease progression and may serve as a surrogate marker for treatment trials.

Improving Surgical Outcome Using Diffusion Tensor Imaging Techniques in Deep Brain Stimulation.

Recent advances in surgical imaging include the use of diffusion tensor imaging (DTI) in deep brain stimulation (DBS) and provide a detailed view of the white matter tracts and their connections which are not seen with conventional magnetic resonance imaging. Given that the efficacy of DBS depends on the precise and accurate targeting of these circuits, better surgical planning using information obtained from DTI may lead to improved surgical outcome. We aim to review the available literature to evaluate the efficacy of such a strategy. A search of PubMed was performed to identify all articles using the search terms "(diffusion tractography OR diffusion tensor imaging OR DTI) AND (deep brain stimulation OR DBS)." Studies were included if DTI was used and clinical outcomes were reported. We identified 35 studies where the use of DTI in DBS was evaluated. The most studied pathology was movement disorders (17 studies), psychiatric disorders (11 studies), and pain (7 studies). The overall responder rates for tremor reduction was 70.0% (SD = 26.1%) in 69 patients, 36.5% (SD = 19.1%) for obsessive-compulsive disorder in 9 patients, 48.3% (SD = 40.0%) for depression in 40 patients, and 49.7% (SD = 35.1%) for chronic pain in 23 patients. The studies reviewed show that the use of DTI for surgical planning is feasible, provide additional information over conventional targeting methods, and can improve surgical outcome. Patients in whom the DBS electrodes were within the DTI targets experienced better outcomes than those in whom the electrodes were not. Many current studies are limited by their small sample size or retrospective nature. The use of DTI in DBS planning appears underutilized and further studies are warranted given that surgical outcome can be optimized using this non-invasive technique.

Visualization of kidney fibrosis in diabetic nephropathy by long diffusion tensor imaging MRI with spin-echo sequence

Renal fibrosis (RF) is an indicator for progression of chronic kidney disease (CKD). Although diabetic nephropathy (DN) is the leading cause of CKD and end-stage renal disease in Western populations, the ability of MRI to evaluate RF in DN patients has not been determined. As a first step to identify possible MRI methods for RF evaluation, we examined the use of diffusion tensor imaging (DTI) MRI to evaluate RF in a rat model of DN (SHR/NDmcr-cp(cp/cp): SHR/ND). The signal-to-noise ratio in DTI MRI was enhanced using a spin-echo sequence, and a special kidney attachment was developed for long-term stabilization. The changes in renal temperature and blood flow during measurement were minimal, suggesting the feasibility of this method. At 38 weeks of age, RF had aggressively accumulated in the outer stripe (OS) of the outer medulla. FA maps showed that this method was successful in visualizing and evaluating fibrosis in the OS of the SHR/ND rat kidney (r = 0.7697, P = 0.0126). Interestingly, in the FA color maps, the directions of water molecule diffusion in RF were random, but distinct from conventional water diffusion in brain neuron fibers. These findings indicate that DTI MRI may be able to evaluate RF in CKD by DN.

Application of neurite orientation dispersion and density imaging or diffusion tensor imaging to quantify the severity of cervical spondylotic myelopathy and to assess postoperative neurologic recovery

Background ContextSurgical outcome and the severity of cervical spondylotic myelopathy (CSM) are unpredictable and cannot be estimated by conventional anatomical magnetic resonance imaging (MRI). The utility of diffusion tensor imaging (DTI) to quantify the severity of CSM and to assess postoperative neurologic recovery has been investigated. However, whether conventional DTI should be applied in a clinical setting remains controversial. Neurite orientation dispersion and density imaging (NODDI) is a recently introduced model-based diffusion-weighted MRI technique that quantifies specific microstructural features related directly to neuronal morphology. However, there are as yet few clinical applications of NODDI reported. Indeed, there are no reports to indicate NODDI is useful for diagnosing CSM. Study DesignThis is a retrospective cohort study using consecutive patients. PurposeThe objective of this study was to evaluate the utility of NODDI and conventional DTI for detecting changes in the spinal cord microstructure. In particular, this study aimed to quantify the preoperative severity of CSM and to assess postoperative neurologic recovery from this myelopathy. Patient SampleWe included 27 consecutive patients with a nontraumatic cervical lesion from CSM who underwent laminoplasty at a single institution between April 2012 and April 2015. The patients underwent MRI before and approximately 2 weeks after surgery. Outcome MeasuresIn addition to conventional DTI metrics, we evaluated the intracellular volume fraction (ICVF) and the orientation dispersion index (ODI), which are metrics derived from NODDI. The 10-second grip and release test and the Japanese Orthopaedic Association scoring system were used before and 1 year after surgery to assess neurologic outcome. Materials and MethodsNeurite orientation dispersion and density imaging and conventional DTI values were measured at the C2–C3 intervertebral level (control value) and at the most compressed levels (C3–C7 intervertebral levels) were measured. The changes in these values pre- and postoperative were demonstrated. Correlations between NODDI and conventional DTI values and clinical outcome were determined. ResultsPreoperative fractional anisotropy was significantly correlated with the severity of neural damage, but not with postoperative neurologic recovery. No significant correlation could be found between the preoperative ICVF, the ODI, the apparent diffusion coefficient, and the severity of the preoperative neurologic dysfunction. Preoperative ICVF was most strongly correlated with the severity of neurologic dysfunction and postoperative neurologic recovery. ConclusionsConventional DTI may be applied clinically to assess the severity of myelopathy. Neurite orientation dispersion and density imaging may be more valuable than conventional DTI to predict outcome following surgery in patients with CSM.

Diffusion Tensor Imaging and Fiber Tractography of Pediatric Posterior Fossa Malformations

Diffusion tensor imaging (DTI) is an advanced MR imaging technique that provides noninvasive qualitative and quantitative information about the white matter microarchitecture. DTI and fiber tractography have been increasingly used in the past decade to investigate the microstructural neuroarchitecture of posterior fossa malformations. This article aimed to review DTI and fiber tractography findings in several posterior fossa malformations, and highlighted the added value of DTI and fiber tractography compared with conventional MR imaging. DTI and fiber tractography may provide information that is helpful to better understand the pathogenesis of selected posterior fossa malformations. In addition, DTI may elucidate the anatomic role of the cerebellum for neurocognitive functions in children with posterior fossa malformations and DTI scalars of the cerebellar, and brain stem white matter tracts may serve as a predictive biomarker for cognitive outcome. Finally, quantitative DTI analysis of cerebellar and brain stem white matter tracts may help to select candidates for therapeutic interventions and may enable monitoring of the therapy response. Learning Objective: To recognize the utility of diffusion tensor imaging and fiber tractography to study malformations of the posterior fossa and highlight the additional information that diffusion tensor imaging and fiber tractography may provide compared with conventional MR imaging sequences.