Characterization complex collagen fiber architecture in knee joint using high‐resolution diffusion imaging

Abstract

School of Medicine (to N.W and C.E.S.).Purpose: To evaluate the complex fiber orientations and 3D collagen fiber network of knee joint connective tissues, including ligaments, muscle, articular cartilage, and meniscus using high spatial and angular resolution diffusion imaging. Methods: Two rat knee joints were scanned using a modified 3D diffusion-weighted spin echo pulse sequence with the isotropic spatial resolution of 45 μm at 9.4T. The b values varied from 250 to 1250 s/mm 2 with 31 diffusion encoding directions for 1 rat knee. The b value was fixed to 1000 s/mm 2 with 147 diffusion encoding directions for the second knee. Both the diffusion tensor imaging (DTI) model and generalized Q-sampling imaging (GQI) method were used to investigate the fiber orientation distributions and tractography with the validation of polarized light microscopy. Results: To better resolve the crossing fibers, the b value should be great than or equal to 1000 s/mm 2 . The tractography results were comparable between the DTI model and GQI method in ligament and muscle. However, the tractography exhibited apparent difference between DTI and GQI in connective tissues with more complex collagen fibers network, such as cartilage and meniscus. In articular cartilage, there were numerous crossing fibers found in superficial zone and transitional zone. Tractography generated with GQI also resulted in more intact tracts in articular cartilage than DTI. Conclusion: High-resolution diffusion imaging with GQI method can trace the complex collagen fiber orientations and architectures of the knee joint at microscopic resolution.

Effects of Angular Resolution and b Value on Diffusion Tensor Imaging in Knee Joint

“…The minimum AR of FA and MD for meniscus is higher than other connective tissues, probably because of the complex collagen architecture in meniscus. 26…”

“…24,25 Compared with T2 and QSM, DTI estimates the fiber direction by detecting the signal decay at different diffusion gradient directions with no need to physical rotate the specimen or subject. 26-30 Diffusion tractography of the anterior cruciate ligament (ACL) graft has been proved to be feasible on clinical 3-T MRI scanners and can provide a reliable estimation of quantitative diffusion indices of the ACL graft. 27 DTI-based tractography of Achilles tendon affords a noninvasive method to detect the tendinopathy-induced changes to microstructure integrity.…”

Effect of b Value on Imaging Quality for Diffusion Tensor Imaging of the Spinal Cord at Ultrahigh Field Strength

“…The EM between the point at b = 200 s/mm 2 and the axis origin was the longest (EM = 1.242584), followed by b = 900 s/mm 2 (EM = 1.004105) and b = 800 s/mm 2 (EM = 0.994274). Considering the insufficient sensitivity of low b value for the detection of microstructure [ 17 , 18 ], b = 900 s/mm 2 can be thought of as the most appropriate b value for rat spinal cord DTI scan at 7 T.…”

Characterization of anisotropic T2W signals from human knee femoral cartilage: The magic angle effect on a spherical surface

“…One of the confounding factors would be a poorly defined cartilage-bone interface. In principle, the developed advanced MR imaging methods such as diffusion and susceptibility tensor imaging techniques 46,47 could provide more accurate collagen fibril orientation information, albeit at the cost of scanning times and the efforts involved in image postprocessing. Second, human knee articular cartilage network microstructures are age-dependent, 30 while the femoral cartilage studied in this work was from an adult subject's knee.…”