Diffusion-weighted and diffusion tensor magnetic resonance brain imaging: Principles and applications

Diffusion Weighted Imaging (DWI) is one of the most recent products of Magnetic Resonance (MR) technology evolution. DWI has been proposed as a noninvasive tool for evaluating structural and physiologic states in biologic tissues as hyperacute ischemic changes within brain tissue. Recently, its more complex and detailed evolution, Diffusion Tensor Imaging (DTI), has been introduced and its clinical applications are the evaluation of anatomical structures and pathologic processes in white matter. White matter quantitative maps that indicate the integrity of brain tissue, color map, and tractography that identifies macroscopic three-dimensional architecture of fiber tracts (e.g., projections and association pathways) can be obtained with DTI. Diffusion weighted imaging visualization techniques (ADC and Trace) are applied for the study of stroke, in the differential diagnosis of expansive lesions (e.g. epidermoid vs. arachnoid cyst) and in detecting traumatic and other lesions associated with restricted diffusion (e.g. MS plaques). On the other hand, DTI provides the identification of abnormalities in the otherwise normal appearing white matter with the understanding of the organization of the fibers, both in tumors and in other cortical or white matter diseases (including stroke, dementias, demyelinating-dismyelinating diseases, epilepsy, schizophrenia). Furthermore, in combination with functional MR, DTI might contribute to the comprehension of brain development, aging and connectivity, thus having a significant impact on brain functional studies.