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White matter mapping using diffusion tensor MRI
C R Tench1, P S Morgan, M Wilson
1Division of Clinical Neurology, University Hospital, Nottingham, UK. msxct@nottingham.ac.uk
Abstract:
Diffusion tensor MRI is used to define trajectories that reflect the long-range order of in vivo white matter (WM) fiber tracts. Fiber tracking is particularly prone to cumulative error from noise and partial volume along the length of the trajectory paths, but the overall shape of each path is anatomically meaningful. By considering only the long-range similarity of path shapes, a method of constructing 3D maps of specific WM structures has been developed. A trajectory is first computed from an operator-selected seed voxel, located within the anatomical structure of interest (SOI). Voxels from the same structure are then automatically identified based on the similarity of trajectory path shapes, assessed using Pearson's correlation coefficient. The corpus callosum and pyramidal tracts in 14 patients with multiple sclerosis, and in 10 healthy controls were mapped by this method, and the apparent diffusion coefficient (ADC) was measured. The ADC was significantly higher in patients than in controls, and higher in the corpus callosum than in the pyramidal tracts for both groups. Using this method the different functional structures in the WM may be identified and mapped. Within these maps, MRI parameters can be measured for subsequent comparison with relevant clinical data.
Insights
This study introduces a novel diffusion tensor MRI method to map white matter (WM) fiber tracts by analyzing trajectory shape similarity. This technique accurately identifies WM structures and measures diffusion parameters for clinical correlation.
Area of Science:
- Neuroimaging
- Biomedical Engineering
- Radiology
Background:
- Diffusion tensor MRI (DTI) is crucial for visualizing in vivo white matter (WM) fiber tracts.
- Fiber tracking methods are susceptible to cumulative errors, impacting trajectory accuracy.
- The anatomical significance of trajectory path shapes offers a basis for improved WM structure mapping.
Purpose of the Study:
- To develop and validate a novel DTI-based method for constructing 3D maps of specific WM structures.
- To assess the utility of this method in differentiating WM structures and measuring diffusion parameters.
Main Methods:
- A novel DTI analysis approach was developed, focusing on long-range similarity of trajectory path shapes.
- Trajectories were initiated from seed voxels within the structure of interest (SOI).
- Voxels belonging to the same WM structure were identified using Pearson's correlation coefficient to assess trajectory shape similarity.
Main Results:
- The method successfully mapped the corpus callosum and pyramidal tracts in multiple sclerosis patients and healthy controls.
- Apparent diffusion coefficient (ADC) values were significantly higher in patients compared to controls.
- ADC values were higher in the corpus callosum than in the pyramidal tracts across both groups.
Conclusions:
- This DTI-based method enables accurate identification and 3D mapping of distinct WM structures.
- The technique allows for the measurement of MRI parameters within mapped WM structures for clinical data correlation.
- This approach holds promise for advancing the understanding of WM alterations in neurological conditions.