- Diffusion Tensor Imaging (DTI) is an advanced magnetic resonance imaging (MRI) technique that enables the visualization and quantification of the diffusion of water molecules in biological tissues, particularly in the white matter of the brain. Unlike conventional MRI, which provides anatomical details, DTI reveals microstructural properties of tissues by measuring how water molecules move along different directions within the brain. This makes it uniquely valuable for mapping the orientation and integrity of white matter tracts, which are bundles of axons that connect different regions of the brain.
- Water diffusion in brain tissue is anisotropic, meaning it varies depending on the direction—especially in white matter, where the movement of water is more restricted across axons than along them due to the presence of myelin sheaths and cell membranes. DTI uses this property to construct diffusion tensors, which are mathematical models representing the 3D shape of water diffusion in each voxel (volume pixel) of the brain. From these tensors, several key parameters can be derived, including fractional anisotropy (FA), which measures the degree of directionality of diffusion, and mean diffusivity (MD), which reflects the overall mobility of water molecules.
- DTI is particularly important in neuroscience and clinical neurology because it enables noninvasive mapping of the brain’s connectivity, a field known as tractography. Tractography uses DTI data to reconstruct the trajectories of white matter fibers, helping researchers and clinicians visualize how different brain regions are linked. This is essential for understanding normal brain development, cognitive function, and neurological or psychiatric diseases. For instance, reduced FA values can indicate white matter damage, such as in multiple sclerosis, traumatic brain injury, stroke, or Alzheimer’s disease.
- In neurosurgical planning, DTI is used to avoid critical white matter pathways during brain surgery, reducing the risk of impairing essential functions such as language, motor control, or vision. In psychiatric research, DTI has helped identify structural abnormalities in conditions like schizophrenia, autism spectrum disorder, and major depressive disorder, offering clues about disrupted brain connectivity that may underlie behavioral symptoms.
- Although powerful, DTI also has limitations. It assumes a single dominant fiber direction per voxel, which can be problematic in areas where multiple fiber tracts cross or converge. This can lead to inaccuracies in tractography and interpretation. Advanced variants such as diffusion spectrum imaging (DSI) or constrained spherical deconvolution (CSD) have been developed to address these complexities and provide more accurate modeling of fiber orientations.
