The addition of preoperative DTI to neuronavigation has been shown, in a large prospective study, to increase tumor resection and survival and to decrease neurologic morbidity. DTI has also been applied for neurosurgical planning and navigation. Recent investigations have attempted to model the human “connectome” by analyzing structural versus functional brain connectivity as measured by DTI and functional MRI. Anatomical investigations have been undertaken regarding for example the structure of the language network, the asymmetry of the white matter in twins and siblings, and the location, asymmetry, and variability of the fiber tracts. It has been applied to a tremendous variety of neuroscientific studies (see reviews in ) including schizophrenia, traumatic brain injury, multiple sclerosis, autism, and aging. Note however, that the diffusion tensor is not able to fully describe crossing of the fiber tracts. 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. The introduction of the diffusion tensor model allowed, for the first time, a rotationally invariant description of the shape of water diffusion. 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. Before DTI, diffusion MRI had developed from research in diffusion nuclear magnetic resonance. The diffusion tensor was originally proposed for use in magnetic resonance imaging (MRI) by Peter Basser in 1994. 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.ġ Why DTI? A brief history of DTI and its impact on clinical research We especially recommend the new diffusion MRI textbook, the introductory paper on fiber tracts and tumors, the white matter atlas book, and the review of potential pitfalls in DTI analysis. Wherever possible, pointers will be provided to more in-depth technical articles or books for further reading. We have tried to include equations for completeness but they are not necessary for understanding the paper. 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. Diffusion tensor magnetic resonance imaging (DTI) is a relatively new technology that is popular for imaging the white matter of the brain.
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