Which imaging modality best maps neural tracts to assess white matter integrity?

• A. T1-weighted MRI
• B. CT angiography
• C. Diffusion Tensor Imaging
• D. Ultrasound

Answer: (C)

The key idea is that white matter integrity is best revealed by how water moves inside brain tissue. In white matter, water tends to diffuse most easily along the length of axons and less across them, because the myelin and membranes restrict sideways diffusion. Diffusion Tensor Imaging uses diffusion-weighted MRI to measure this directional diffusion, capturing a diffusion tensor for each voxel. From these tensors, tractography can reconstruct the pathways of white-matter tracts and metrics like fractional anisotropy quantify how organized or damaged the fibers are. That capability—mapping fiber pathways and assessing microstructural integrity—is what makes diffusion tensor imaging the best choice for this purpose.

T1-weighted MRI provides anatomy but not diffusion direction or tract structure. CT angiography visualizes blood vessels, not neural tracts. Ultrasound has limited penetration and resolution for detailed white-matter tract mapping in the brain.