Tractography of Porcine Meniscus Microstructure Using High-Resolution Diffusion Magnetic Resonance Imaging

Area of Science:

• Biomedical Engineering
• Medical Imaging
• Orthopedics

Background:

• The meniscus's collagen fiber architecture is crucial for knee joint function.
• Noninvasive methods to evaluate this complex 3D structure are needed.
• Diffusion MRI offers potential for microstructural tissue assessment.

Purpose of the Study:

• To evaluate the 3D collagen fiber architecture of the porcine meniscus noninvasively.
• To visualize the complex collagen network using diffusion MRI and tractography.
• To quantify diffusion tensor imaging (DTI) metrics across different meniscal zones and parts.

Main Methods:

• Porcine meniscal specimens scanned using a 3D diffusion-weighted spin-echo sequence at 7.0 T.
• Tractography used to reveal collagen fiber alignment and visualize the 3D network.
• Automatic segmentation divided the meniscus into zones (Red-Red, Red-White, White-White) and parts (anterior, body, posterior) for DTI metric quantification.

Main Results:

• Diffusion tractography successfully visualized the 3D collagen fiber architecture, showing radial and circumferential fibers.
• Strong zonal-dependent diffusion properties observed: fractional anisotropy (FA) increased from 0.13 (White-White) to 0.26 (Red-Red); radial diffusivity (RD) decreased from 1.0 × 10^-3 mm²/s (White-White) to 0.7 × 10^-3 mm²/s (Red-Red).
• Analysis revealed weak connections between White-White and Red-Red zones, with the body part showing high connectivity to anterior and posterior parts.

Conclusions:

• Diffusion MRI, combined with tractography, provides a noninvasive method to characterize the 3D collagen fiber architecture of the meniscus.
• The study demonstrates zonal differences in meniscal diffusion properties, correlating with collagen fiber orientation.
• This technique offers a complementary approach for assessing meniscus integrity and understanding its structural organization.