Diffusion Tensor Imaging

Neurosurgery ◽  
2016 ◽  
Vol 79 (6) ◽  
pp. 786-793 ◽  
Author(s):  
Süleyman Sener ◽  
Wim Van Hecke ◽  
Bart F.E. Feyen ◽  
Gregory Van der Steen ◽  
Pim Pullens ◽  
...  
Keyword(s):  
Diffusion Tensor Imaging ◽  
Fractional Anisotropy ◽  
Clinical Studies ◽  
Diffusion Tensor ◽  
Mean Diffusivity ◽  
Disease Process ◽  
Whole Brain ◽  
Tract Length ◽  
Severe Tbi ◽  
Dti Tractography

Abstract BACKGROUND: A great need exists in traumatic brain injury (TBI) and aneurysmal subarachnoid hemorrhage (aSAH) for objective biomarkers to better characterize the disease process and to serve as early endpoints in clinical studies. Diffusion tensor imaging (DTI) has shown promise in TBI, but much less is known about aSAH. OBJECTIVE: To explore the use of whole-brain DTI tractography in TBI and aSAH as a biomarker and early endpoint. METHODS: Of a cohort of 43 patients with severe TBI (n = 20) or aSAH (n = 23) enrolled in a prospective, observational, multimodality monitoring study, DTI data were acquired at approximately day 12 (median, 12 days; interquartile range, 12-14 days) after injury in 22 patients (TBI, n = 12; aSAH, n = 10). Whole-brain DTI tractography was performed, and the following parameters quantified: average fractional anisotropy, mean diffusivity, tract length, and the total number of reconstructed fiber tracts. These were compared between TBI and aSAH patients and correlated with mortality and functional outcome assessed at 6 months by the Glasgow Outcome Scale Extended. RESULTS: Significant differences were found for fractional anisotropy values (P = .01), total number of tracts (P = .03), and average tract length (P = .002) between survivors and nonsurvivors. A sensitivity analysis showed consistency of results between the TBI and aSAH patients for the various DTI measures. CONCLUSION: DTI parameters, assessed at approximately day 12 after injury, correlated with mortality at 6 months in patients with severe TBI or aSAH. Similar patterns were found for both TBI and aSAH patients. This supports a potential role of DTI as early endpoint for clinical studies and a predictor of late mortality.

Influence of fractional anisotropy thresholds on diffusion tensor imaging tractography of the periprostatic neurovascular bundle and selected pelvic tissues: do visualized tracts really represent nerves?

2016 ◽  
Vol 58 (4) ◽  
pp. 472-480 ◽  
Author(s):  
Alexander DJ Baur ◽  
Tareef Daqqaq ◽  
Federico Collettini ◽  
Timm Denecke ◽  
Bernd Hamm ◽  
...  
Keyword(s):  
Diffusion Tensor Imaging ◽  
Sciatic Nerve ◽  
Urinary Bladder ◽  
Fractional Anisotropy ◽  
Diffusion Tensor ◽  
Neurovascular Bundle ◽  
Tract Length ◽  
Nerve Tracts ◽  
Dti Tractography ◽  
The Impact

Background Diffusion tensor imaging (DTI) tractography has recently been shown to successfully visualize periprostatic tracts allegedly representing the neurovascular bundle. Purpose To examine the impact of different fractional anisotropy (FA) thresholds on the results of DTI tractography in the male pelvis as well as to evaluate the resulting specificity for nerve tracts. Material and Methods Ten healthy male volunteers were examined at 3 Tesla. DTI tractography was performed based on seed points placed circularly around the prostate, in the rectoprostatic angle, the peripheral zone of the prostate, the sciatic nerve, and in addition the urinary bladder using FA thresholds of 0.20, 0.05, and 0.01. DTI tract number and DTI tract length measured with different FA thresholds were compared. ANOVA with repeated measures was used for statistics. Results DTI tract number and tract length were significantly dependent on FA thresholds. While a FA threshold of 0.20 visualized the typical distribution of DTI tracts in the sciatic nerve, a FA threshold of ≤0.05 was necessary to yield results visually mimicking the distribution of nerve tracts in the NVB. However, with such low FA thresholds even in the filled urinary bladder DTI tracts could be visualized. With FA thresholds of 0.20, the number and length of periprostatic DTI tracts did not differ from those measured within the prostate. Conclusion DTI tractography can be used to visualize DTI tracts periprostatically. However, one may doubt that these DTI tracts represent nerve tracts and that the periprostatic neurovascular bundle can be evaluated in a meaningful way with the current methods available.

scholarly journals Diffusion Tensor Imaging of the Kidneys: Influence of b-Value and Number of Encoding Directions on Image Quality and Diffusion Tensor Parameters

2013 ◽  
Vol 3 ◽  
pp. 53 ◽  
Author(s):  
Natalie C. Chuck ◽  
Günther Steidle ◽  
Iris Blume ◽  
Michael A. Fischer ◽  
Daniel Nanz ◽  
...  
Keyword(s):  
Diffusion Tensor Imaging ◽  
Image Quality ◽  
Fractional Anisotropy ◽  
Diffusion Tensor ◽  
Mean Diffusivity ◽  
Renal Medulla ◽  
Whole Body ◽  
Acquisition Time ◽  
Data Sets ◽  
B Values

Objectives: The purpose of this study was to evaluate to which degree investment of acquisition time in more encoding directions leads to better image quality (IQ) and what influence the number of encoding directions and the choice of b-values have on renal diffusion tensor imaging (DTI) parameters. Material and Methods: Eight healthy volunteers (32.3 y ± 5.1 y) consented to an examination in a 1.5T whole-body MR scanner. Coronal DTI data sets of the kidneys were acquired with systematic variation of b-values (50, 150, 300, 500, and 700 s/mm2) and number of diffusion-encoding directions (6, 15, and 32) using a respiratory-triggered echo-planar sequence (TR/TE 1500 ms/67 ms, matrix size 128 × 128). Additionally, two data sets with more than two b-values were acquired (0, 150, and 300 s/mm2 and all six b-values). Parametrical maps were calculated on a pixel-by-pixel basis. Image quality was determined with a reader score. Results: Best IQ was visually assessed for images acquired with 15 and 32 encoding directions, whereas images acquired with six directions had significantly lower IQ ratings. Image quality, fractional anisotropy, and mean diffusivity only varied insignificantly for b-values between 300 and 500 s/mm2. In the renal medulla fractional anisotropy (FA) values between 0.43 and 0.46 and mean diffusivity (MD) values between 1.8-2.1 × 10-3 mm2/s were observed. In the renal cortex, the corresponding ranges were 0.24-0.25 (FA) and 2.2-2.8 × 10-3 mm2/s (MD). Including b-values below 300 s/mm2, notably higher MD values were observed, while FA remained constant. Susceptibility artifacts were more prominent in FA maps than in MD maps. Conclusion: In DTI of the kidneys at 1.5T, the best compromise between acquisition time and resulting image quality seems the application of 15 encoding directions with b-values between 300 and 500 s/mm2. Including lower b-values allows for assessment of fast diffusing spin components.

scholarly journals Global diffusion tensor imaging derived metrics differentiate glioblastoma multiforme vs. normal brains by using discriminant analysis: introduction of a novel whole-brain approach

2014 ◽  
Vol 48 (2) ◽  
pp. 127-136 ◽  
Author(s):  
Ernesto Roldan-Valadez ◽  
Camilo Rios ◽  
David Cortez-Conradis ◽  
Rafael Favila ◽  
Sergio Moreno-Jimenez
Keyword(s):  
Diffusion Tensor Imaging ◽  
Discriminant Analysis ◽  
Glioblastoma Multiforme ◽  
Predictive Model ◽  
Predictive Accuracy ◽  
Diffusion Tensor ◽  
Mean Diffusivity ◽  
Continuous Variables ◽  
Whole Brain ◽  
Axial Diffusivity

Abstract Background. Histological behavior of glioblastoma multiforme suggests it would benefit more from a global rather than regional evaluation. A global (whole-brain) calculation of diffusion tensor imaging (DTI) derived tensor metrics offers a valid method to detect the integrity of white matter structures without missing infiltrated brain areas not seen in conventional sequences. In this study we calculated a predictive model of brain infiltration in patients with glioblastoma using global tensor metrics. Methods. Retrospective, case and control study; 11 global DTI-derived tensor metrics were calculated in 27 patients with glioblastoma multiforme and 34 controls: mean diffusivity, fractional anisotropy, pure isotropic diffusion, pure anisotropic diffusion, the total magnitude of the diffusion tensor, linear tensor, planar tensor, spherical tensor, relative anisotropy, axial diffusivity and radial diffusivity. The multivariate discriminant analysis of these variables (including age) with a diagnostic test evaluation was performed. Results. The simultaneous analysis of 732 measures from 12 continuous variables in 61 subjects revealed one discriminant model that significantly differentiated normal brains and brains with glioblastoma: Wilks’ λ = 0.324, χ2 (3) = 38.907, p < .001. The overall predictive accuracy was 92.7%. Conclusions. We present a phase II study introducing a novel global approach using DTI-derived biomarkers of brain impairment. The final predictive model selected only three metrics: axial diffusivity, spherical tensor and linear tensor. These metrics might be clinically applied for diagnosis, follow-up, and the study of other neurological diseases.

scholarly journals Heterogeneity of Fractional Anisotropy and Mean Diffusivity Measurements by In Vivo Diffusion Tensor Imaging in Normal Human Hearts

PLoS ONE ◽  
2015 ◽  
Vol 10 (7) ◽  
pp. e0132360 ◽  
Author(s):  
Laura-Ann McGill ◽  
Andrew D. Scott ◽  
Pedro F. Ferreira ◽  
Sonia Nielles-Vallespin ◽  
Tevfik Ismail ◽  
...  
Keyword(s):  
Diffusion Tensor Imaging ◽  
Fractional Anisotropy ◽  
Diffusion Tensor ◽  
Mean Diffusivity ◽  
Diffusivity Measurements ◽  
Normal Human

scholarly journals Perivascular space fluid contributes to diffusion tensor imaging changes in white matter

2018 ◽  
Author(s):  
Farshid Sepehrband ◽  
Ryan P Cabeen ◽  
Jeiran Choupan ◽  
Giuseppe Barisano ◽  
Meng Law ◽  
...  
Keyword(s):  
Diffusion Tensor Imaging ◽  
White Matter ◽  
Fractional Anisotropy ◽  
Diffusion Mri ◽  
Diffusion Tensor ◽  
Diffusion Imaging ◽  
Mean Diffusivity ◽  
Brain Parenchyma ◽  
Perivascular Space ◽  
List Type

AbstractDiffusion tensor imaging (DTI) has been extensively used to map changes in brain tissue related to neurological disorders. Among the most widespread DTI findings are increased mean diffusivity and decreased fractional anisotropy of white matter tissue in neurodegenerative diseases. Here we utilize multi-shell diffusion imaging to separate diffusion signal of the brain parenchyma from fluid within the white matter. We show that unincorporated anisotropic water in perivascular space (PVS) significantly, and systematically, biases DTI measures, casting new light on the biological validity of many previously reported findings. Despite the challenge this poses for interpreting these past findings, our results suggest that multi-shell diffusion MRI provides a new opportunity for incorporating the PVS contribution, ultimately strengthening the clinical and scientific value of diffusion MRI.HighlightsPerivascular space (PVS) fluid significantly contributes to diffusion tensor imaging metricsIncreased PVS fluid results in increased mean diffusivity and decreased fractional anisotropyPVS contribution to diffusion signal is overlooked and demands further investigation

Segmental Diffusion Properties of the Corticospinal Tract and Motor Outcome in Hemiparetic Children With Perinatal Stroke

2017 ◽  
Vol 32 (6) ◽  
pp. 550-559 ◽  
Author(s):  
Jacquie Hodge ◽  
Bradley Goodyear ◽  
Helen Carlson ◽  
Xing-Chang Wei ◽  
Adam Kirton
Keyword(s):  
Diffusion Tensor Imaging ◽  
Fractional Anisotropy ◽  
Corticospinal Tract ◽  
Diffusion Tensor ◽  
Model Development ◽  
Structural Connectivity ◽  
Mean Diffusivity ◽  
Radial Diffusivity ◽  
Perinatal Stroke ◽  
Motor Outcomes

Perinatal stroke injures developing motor systems, resulting in hemiparetic cerebral palsy. Diffusion tensor imaging can explore structural connectivity. We used diffusion tensor imaging to assess corticospinal tract diffusion in hemiparetic children with perinatal stroke. Twenty-eight children (6-18 years) with unilateral stroke underwent diffusion tensor imaging. Four corticospinal tract assessments included full tract, partial tract, minitract and region of interest. Diffusion characteristics (fractional anisotropy, mean, axial, and radial diffusivity) were calculated. Ratios (lesioned/nonlesioned) were compared across segments and to validated long-term motor outcomes (Pediatric Stroke Outcome Measure, Assisting Hand Assessment, Melbourne Assessment). Fractional anisotropy and radial diffusivity ratios decreased as tract size decreased, while mean diffusivity showed consistent symmetry. Poor motor outcomes were associated with lower fractional anisotropy in all segments and radial diffusivity correlated with both Assisting Hand Assessment and Melbourne Assessment. Diffusion imaging of segmented corticospinal tracts is feasible in hemiparetic children with perinatal stroke. Correlations with disability support clinical relevance and utility in model development for personalized rehabilitation.

scholarly journals Reduction of bias in the evaluation of fractional anisotropy and mean diffusivity in magnetic resonance diffusion tensor imaging using region-of-interest methodology

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Youngseob Seo ◽  
Nancy K. Rollins ◽  
Zhiyue J. Wang
Keyword(s):  
Diffusion Tensor Imaging ◽  
Fractional Anisotropy ◽  
Diffusion Tensor ◽  
Signal To Noise Ratio ◽  
Mean Diffusivity ◽  
Region Of Interest ◽  
Superior Temporal Gyrus ◽  
Brain Structures ◽  
Equivalence Test ◽  
Mr Diffusion

Abstract Accurate quantification of fractional anisotropy (FA) and mean diffusivity (MD) in MR diffusion tensor imaging (DTI) requires adequate signal-to-noise ratio (SNR) especially in low FA areas of the brain, which necessitates clinically impractical long image acquisition times. We explored a SNR enhancement strategy using region-of-interest (ROI)-based diffusion tensor for quantification. DTI scans from a healthy male were acquired 15 times and combined into sets with different number of signal averages (NSA = 1–4, 15) at one 1.5-T Philips and three 3-T (Philips, Siemens and GE) scanners. Equivalence test was performed to determine NSA thresholds for bias-free FA and MD quantifications by comparison with reference values derived from images with NSA = 15. We examined brain areas with low FA values including caudate nucleus, globus pallidus, putamen, superior temporal gyrus, and substructures within thalamus (lateral dorsal, ventral anterior and posterior nuclei), where bias-free FA is difficult to obtain using a conventional approach. Our results showed that bias-free FA can be obtained with NSA = 2 or 3 in some cases using ROI-based analysis. ROI-based analysis allows reliable FA and MD quantifications in various brain structures previously difficult to study with clinically feasible data acquisition schemes.

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