Tractography
What is Tractography?
Tractography is a non-invasive imaging technique that plays a crucial role in evaluating neurological disorders. By visualizing and mapping the tracts (pathways of nerve fibers and their electrical signals) in the brain, tractography enables researchers and healthcare professionals to identify abnormalities and disruptions in the brain’s structural connectivity. This helps in early diagnosis, understanding disease progression, and guiding treatment strategies for conditions such as multiple sclerosis, Alzheimer’s disease, stroke, and epilepsy.
Tractography also aids in surgical planning, allowing surgeons to avoid damaging critical neural pathways during brain tumor removal or epilepsy surgery, minimizing the risk of postoperative neurological deficits.
Figure A (Right): Rotational of some tractography, color-coded by the neural function they provide.
How is Tractography Obtained?
Mapping the tractography of the brain typically relies on diffusion-weighted magnetic resonance imaging (DW-MRI), a specialized scan that observes the patterns of diffusion of water molecules in brain tissues. The strength and direction of water diffusion can be constructed into 3D trajectories, represented by hair-like strands, providing a visual reconstruction of the nerve fibers’ pathways through the brain.
Figure B (Left): Tractography fused with an axial brain MR.
How is Tractography Used?
• Investigating Neurological Disorders: Tractography plays a vital role in neuroscience research, especially in studying neurological disorders. By examining the integrity of specific nerve fiber pathways, researchers can identify abnormalities associated with conditions like multiple sclerosis, Alzheimer’s disease, strokes, Autism Spectrum Disorder (ASD), and Parkinson’s disease. This information helps in early diagnosis and understanding disease progression.
• Surgical Planning & Navigation: Tractography is essential in presurgical planning for brain surgeries involving a variety of pathologies like tumors and epilepsy. It allows neurosurgeons to visualize critical white matter tracts carrying sensory, motor, and cognitive information, helping them plan safe surgical approaches and define resection boundaries. Tractography data can also be integrated into surgical navigation systems in the OR, providing real-time guidance during the procedure to avoid damaging important areas.
• FMRI Functional MRI (fMRI): Tractography is often combined with functional magnetic resonance imaging (fMRI) to explore the relationship between brain function and structural connectivity. An fMRI study involves participants performing specific cognitive or motor tasks outside the scanner, while their brain activity is recorded using fMRI. Combining this information with tractography gives insight into which groups of nerve fibers are involved in specific body functions.
Figure C (Right): Tractography is used in a surgical guidance software, that assists with surgical planning and navigation.
