Diffusion Tensor Imaging: A Review for Pediatric Researchers and Clinicians

Abstract

Diffusion tensor imaging (DTI) is a magnetic resonance imaging technique that allows for the visualization and characterization of the white matter tracts of the brain in vivo. DTI does not assess white matter directly. Rather, it capitalizes on the fact that diffusion is isotropic (equal in all directions) in cerebral spinal fluid and cell bodies but anisotropic (greater in one direction than the other directions) in axons that comprise white matter. It provides quantitative information about the degree and direction of water diffusion within individual units of volume within the magnetic resonance image, and by inference, about the integrity of white matter. Measures from DTI can be applied throughout the brain or to regions of interest. Fiber tract reconstruction, or tractography, creates continuous 3-dimensional tracts by sequentially piecing together estimates of fiber orientation from the direction of diffusion within individual volume units. DTI has increased our understanding of white matter structure and function. DTI shows nonlinear growth of white matter tracts from childhood to adulthood. Delayed maturation of the white matter in the frontal lobes may explain the continued growth of cognitive control into adulthood. Relative to good readers, adults and children who are poor readers have evidence of white matter differences in a specific region of the temporo-parietal lobe, implicating differences in connections among brain regions as a factor in reading disorder. Measures from DTI changed in poor readers who improved their reading skills after intense remediation. DTI documents injury to white matter tracts after prematurity. Measures indicative of white matter injury are associated with motor and cognitive impairment in children born prematurely. Further research on DTI is necessary before it can become a routine clinical procedure. Index Termsdiffusion tensor imaging; magnetic resonance imaging; tractography; children; white matter development; white matter associations with reading disorder; white matter injury in prematurity NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author ManuscriptContemporary neuroscience conceptualizes complex thoughts and emotions as arising from widely distributed and highly interactive neural networks. [1][2][3][4] Localized cortical regions within the gray matter contribute specialized or semispecialized computations to mental activity, functioning like microprocessors. The structure of these regions can be assessed with conventional magnetic resonance imaging. Activity within these regions during cognitive or emotional processing can be assessed using functional magnetic resonance imaging. Axons arising from cell bodies connect neurons to other neurons. Axons are organized into white matter fiber bundles that link cortical regions, acting like cables connecting the microprocessors. Diffusion tensor imaging is an magnetic resonance imaging technique that allows for the visualization and characterization of white matter tracts in living animals and h...

Diffusion Tensor Imaging of the Normal Pediatric Spinal Cord Using an Inner Field of View Echo-Planar Imaging Sequence

“…This variations pattern can be attributed to the following effects: 1) In the upper cervical spinal cord, there is a higher attenuation of large-diameter axons compared with the upper thoracic region and, consequently, an increased axial (or longitu- dinal) diffusivity (AD). 34,35 Subsequently, all the DTI indices (FA, MD, RA, and Cl) that are proportionally related to AD also showed a decrease in the thoracic region, and the parameters that are inversely proportional to AD showed an increase. This pattern is similar to that reported in other studies involving adult subjects.…”

“…Additional challenges include keeping a child motionless for several minutes without the use of sedation and the absence of normative DTI data for comparison. Although diffusion changes in the pediatric brain have been reported, [33][34][35] no comprehensive study of the pediatric spinal cord has been conducted. Despite these difficulties, DTI parameters were successfully obtained in this study using a well-optimized scanning protocol.…”

Acquisition Guidelines and Quality Assessment Tools for Analyzing Neonatal Diffusion Tensor MRI Data

“…63 Although probabilistic tractography seems more reliable, it remains dependent on the placement of the seed points, which is manually done. 3,12,35,[64][65][66] Although these analytic measurements provide in vivo information about the orientation, organization, and microstructural properties of the cerebral white matter, DTI analysis remains a proxy technique and not a direct visualization of the cerebral white matter. Moreover, because tensor estimations are subject to error, we emphasize the importance of appropriate acquisition settings with regard to gestational age, a quality check before postprocessing, reliable postprocessing techniques, and good knowledge of neuro anatomy.…”

Assessment of diffusion tensor image quality across sites and vendors using the American College of Radiology head phantom

“…DTI is used for quantitative assessment of white matter in many disease states 2 , 3 , 4 . When comparing diffusion tensor data acquired at multiple centers using the same or different vendors, biological differences in tensor metrics may in fact be related to technical factors due to different hardware platforms, software releases, and imaging parameters, as the major vendors of MR have different pulse sequences, parallel imaging techniques, and reconstruction algorithms.…”