Diffusion tractography of the rat knee at microscopic resolution

Area of Science:

• Biomedical Imaging
• Musculoskeletal Research
• Diffusion Tensor Imaging

Background:

• Knee joint imaging requires detailed visualization of complex connective tissues.
• Current imaging methods may lack the resolution to fully characterize microscopic structures.

Purpose of the Study:

• To evaluate whole knee joint tractography using diffusion tensor imaging (DTI) at microscopic resolution.
• To assess articular cartilage, ligaments, meniscus, and growth plate visualization.

Main Methods:

• Acquired 9.4T MRI data from three rat knee joints using a modified 3D diffusion-weighted spin echo sequence.
• Employed 90- and 45-μm isotropic spatial resolutions with varying b values (250-1250 s/mm²).
• Analyzed fractional anisotropy (FA), mean diffusivity (MD), and performed tractography, comparing results with histology.

Main Results:

• DTI metrics (FA, MD) showed consistent results at both 90-μm and 45-μm resolutions.
• Tractography sensitivity varied with spatial resolution, angular resolution, and diffusion weighting.
• 45-μm resolution enabled tracking of cartilage collagen fibers; growth plate and ligament tractography showed dependencies on resolution and b values.

Conclusions:

• High spatial and angular resolution DTI and tractography are valuable for knee joint research.
• This approach enables visualization of collagen fiber orientations.
• It allows for quantitative evaluation of microscopic tissue properties.