Effect of the Maximum Dose on White Matter Fiber Bundles Using Longitudinal Diffusion Tensor Imaging

Area of Science:

• Neuroscience
• Radiology
• Medical Physics

Background:

• Previous radiation therapy (RT) research focused on sparing cortical structures to mitigate neurocognitive effects.
• Understanding radiation damage patterns in whole-brain white matter (WM) is crucial for improving patient outcomes.

Purpose of the Study:

• To develop and apply a methodology for assessing RT-induced damage to whole-brain WM bundles.
• To investigate the temporal, spatial, and dosimetric patterns of WM damage after partial-brain irradiation.

Main Methods:

• Utilized atlas-based, automated WM tractography to analyze diffusion tensor imaging (DTI) data from 33 patients treated with RT.
• Quantified longitudinal changes in DTI indices (axial diffusivity and radial diffusivity) of 22 major WM fiber bundles over 18 months post-RT.
• Performed multivariate linear regression to correlate DTI changes with radiation dose (maximum and mean) and clinical factors.

Main Results:

• Significant dose-dependent changes in axial diffusivity (AD) or radial diffusivity (RD) were observed in 12 of 22 WM bundles.
• Decreased AD or RD in 9 elongated tracts correlated significantly with maximum radiation doses received, indicating a serial damage pattern.
• WM damage effects were more pronounced in older female patients compared to younger male patients.

Conclusions:

• Maximum radiation dose to elongated WM bundles is a significant factor in causing post-RT white matter damage.
• Further validation and correlative studies are needed to assess the impact of sparing these WM bundles on neurocognitive function preservation.