Diffusion tensor imaging

Diffusion Tensor Imaging DTI studies are increasingly popular among clinicians and researchers as they provide unique insights into brain network connectivity.

Diffusion tensor imaging DTI allows a live look into the microstructure of white matter in the brain and is an important complement to volumetric studies of specific structures such as the amygdala. DTI may be particularly informative for the study of autism because it has been speculated that white matter the connections between neurons defects may be even more pronounced than gray matter defects for affected individuals. Furthermore, in contrast to gray matter, white matter volume continues to increase across childhood and adolescence, thus allowing for analyses of growth curves and changes specific to the microstructure of axons. See papers by Courchesne, et al. Studies that utilize DTI technology generally describe two characteristics of white matter within a particular "voxel" in the brain:. Diffusion imaging takes advantage of the fact that the myelin sheath surrounding an axon restricts the diffusion of water perpendicular to the axon, while allowing relatively free diffusion of water parallel to the axon.

Diffusion tensor imaging

Federal government websites often end in. The site is secure. Diffusion tensor magnetic resonance imaging DTI is a relatively new technology that is popular for imaging the white matter of the brain. The goal of this review is to give a basic and broad overview of DTI such that the reader may develop an intuitive understanding of this type of data, and an awareness of its strengths and weaknesses. We have tried to include equations for completeness but they are not necessary for understanding the paper. Wherever possible, pointers will be provided to more in-depth technical articles or books for further reading. We especially recommend the new diffusion MRI textbook [ 1 ], the introductory paper on fiber tracts and tumors [ 2 ], the white matter atlas book [ 3 ], and the review of potential pitfalls in DTI analysis [ 4 ]. In the rest of this article we will address basic questions about DTI the what, why, and how of DTI , followed by a discussion of issues in interpretation of DTI, and finally an overview of more advanced diffusion imaging methods and future directions. The diffusion tensor was originally proposed for use in magnetic resonance imaging MRI by Peter Basser in [ 5 , 6 ]. Prior to the introduction of the diffusion tensor model, to measure anisotropic diffusion the orientation of the axons in a tissue sample had to be known, so only fixed samples such as the axon of the giant squid could be scanned [ 10 ]. The introduction of the diffusion tensor model allowed, for the first time, a rotationally invariant description of the shape of water diffusion. The invariance to rotation was crucial because it enabled application of the DTI method to the complex anatomy of the fiber tracts in the human brain [ 11 ]. Note however, that the diffusion tensor is not able to fully describe crossing of the fiber tracts [ 12 , 13 ]. The popularity of DTI has been enormous. It has been applied to a tremendous variety of neuroscientific studies see reviews in [ 14 , 15 , 16 ] including schizophrenia [ 17 ], traumatic brain injury [ 18 ], multiple sclerosis [ 19 , 20 ], autism [ 21 ], and aging [ 22 ].

Diffusion-tensor MR imaging and tractography: exploring brain microstructure and connectivity.

Federal government websites often end in. The site is secure. Diffusion tensor imaging DTI is a promising method for characterizing microstructural changes or differences with neuropathology and treatment. The diffusion tensor may be used to characterize the magnitude, the degree of anisotropy, and the orientation of directional diffusion. This review addresses the biological mechanisms, acquisition, and analysis of DTI measurements.

Advanced magnetic resonance MR neuroimaging modalities are becoming more available and useful as their value in the diagnosis and prognosis of central nervous system diseases is more fully studied and understood. Specifically, diffusion tensor imaging DTI has become increasingly studied and utilized in recent years. It has become incorporated by many radiologists into routine clinical practice, with most research performed on traumatic brain injury TBI. DTI is a variant of diffusion-weighted imaging DWI that utilizes a tissue water diffusion rate for image production. The first application of DWI to the human brain was performed in and since has become the gold standard for detecting acute stroke. DTI does not require contrast and is available on almost all modern MR scanners with relatively quick scan times for this sequence.

Diffusion tensor imaging

Purpose: This study aimed to investigate the diagnostic performance of diffusion kurtosis imaging DKI and diffusion tensor imaging DTI in identifying aberrations in the corticospinal tract CST , whilst elucidating the relationship between abnormalities of CST and patients' motor function. The receiver operating characteristic curve was performed to investigate the diagnostic efficacy of DKI and DTI metrics. Results: In Group 1, a significantly lower fractional anisotropy, radial kurtosis and mean kurtosis, and a higher mean diffusivity were found in the ipsilateral CST as compared to the contralateral CST. Significantly higher relative axial diffusivity, relative radial diffusivity, and relative mean diffusivity rMD were found in Group 1, as compared to Group 2. The relative volume of ipsilateral CST abnormalities higher than the maximum value of mean kurtosis combined with rMD exhibited the best diagnostic performance in distinguishing dysfunction of CST with an AUC of 0. Keywords: corticospinal tract; diffuse glioma; diffusion kurtosis imaging; diffusion tensor imaging.

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The normalization procedure is crucial for VBA analysis and the result of a misalignment can be unpredictable. Neuroimage 36, — This is particularly challenging in DTI due to its highly directional and topographical nature. A special kind of DWI, diffusion tensor imaging DTI , has been used extensively to map white matter tractography in the brain. Several in-vivo studies have shown that the choice of software and functions applied directed at correcting artefacts from arising from e. Once we have measured the voxel from six or more directions and corrected for attenuations due to T2 and T1 effects, we can use information from our calculated ellipsoid tensor to describe what is happening in the voxel. The same matrix of numbers can have a simultaneous second use to describe the shape and orientation of an ellipse and the same matrix of numbers can be used simultaneously in a third way for matrix mathematics to sort out eigenvectors and eigenvalues as explained below. Diffusion spectrum magnetic resonance imaging DSI tractography of crossing fibers. The whole formula for FA looks like this:. But in clinical research today a higher number of images are almost always used. Diffusion tensor imaging of white matter after cranial radiation in children for medulloblastoma: correlation with IQ. Promoted articles advertising. Finsler tractography for white matter connectivity analysis of the cingulum bundle.

Diffusion MRI is used widely to probe microstructural alterations in neurological and psychiatric disease. However, ageing and neurodegeneration are also associated with atrophy, which leads to artefacts through partial volume effects due to cerebrospinal-fluid contamination CSFC.

Functional MRI gives detailed pictures of brain activity. Chen, B. The cingulum can be seen in blue, and the posterior limb of the internal capsule in green. Protocol error artifacts in MRI: sources and remedies revisited. In voxels with high planar or spherical measure, the principal eigenvector will not always match an underlying fiber tract direction where tracts cross the eigenvector may point to neither one. The particular errors depend strongly on the tractography algorithm employed, and on the type of diffusion data used DTI versus higher-order models. The MD and trace measured in ventricles or in edema can be higher than in water due to fluid flow or enhanced perfusion, respectively [ 43 ]. Diffusion tensor analysis of peritumoral edema using lambda chart analysis indicative of the heterogeneity of the microstructure within edema. Beaulieu, C. White matter plasticity in the corticospinal tract of musicians: a diffusion tensor imaging study. Analysis of partial volume effects in diffusion-tensor MRI. Studying connections in the living human brain with diffusion MRI. The MRI scanner measures this signal difference and displays the activity as a colored area Fig.