Track orientation density imaging (TODI) and track orientation distribution (TOD) based tractography

Area of Science:

• Neuroimaging
• Diffusion MRI
• Computational Neuroscience

Background:

• Fiber tractography methods generate plausible tractograms representing complex fiber architecture.
• Modern techniques use probabilistic approaches to handle uncertainty, with tractograms as samples of possible tracks.
• Track-density imaging (TDI) captures the spatial distribution of tractograms.

Purpose of the Study:

• To propose an extension of TDI into the 5D spatio-angular domain, named track orientation density imaging (TODI).
• To capture the full track orientation distribution (TOD) with spatial and angular super-resolution capabilities.
• To explore TOD-based fiber tractography for improved robustness.

Main Methods:

• Extension of track-density imaging (TDI) to the 5D spatio-angular domain, creating track orientation density imaging (TODI).
• Evaluation of TODI using in vivo human data, an in silico numerical phantom, and a tractography phantom.
• Development of TOD-based fiber tractography utilizing short-tracks TOD for guidance.

Main Results:

• TODI captures the full track orientation distribution (TOD) with enhanced spatial and angular resolution.
• TOD demonstrates superior regional spatio-angular consistency compared to fiber orientation distribution (FOD) from constrained spherical deconvolution (CSD).
• TOD-based fiber tractography significantly improves the robustness of targeted and whole-brain tractography.

Conclusions:

• TODI is a versatile tool for capturing detailed track orientation information.
• The track-like local support (TLS) derived from TOD can guide tractography effectively.
• TODI and TOD-based methods represent a significant advancement in fiber tractography applications.