T₂ and T_1ρ MRI in articular cartilage systems

Abstract

T2 and T1rho have potential to nondestructively detect cartilage degeneration. However, reports in the literature regarding their diagnostic interpretation are conflicting. In this study, T2 and T1rho were measured at 8.5 T in several systems: 1) Molecular suspensions of collagen and GAG (pure concentration effects): T2 and T1rho demonstrated an exponential decrease with increasing [collagen] and [GAG], with [collagen] dominating. T2 varied from 90 to 35 ms and T1rho from 125 to 55 ms in the range of 15-20% [collagen], indicating that hydration may be a more important contributor to these parameters than previously appreciated. 2) Macromolecules in an unoriented matrix (young bovine cartilage): In collagen matrices (trypsinized cartilage) T2 and T1rho values were consistent with the expected [collagen], suggesting that the matrix per se does not dominate relaxation effects. Collagen/GAG matrices (native cartilage) had 13% lower T2 and 17% lower T1rho than collagen matrices, consistent with their higher macromolecular concentration. Complex matrix degradation (interleukin-1 treatment) showed lower T2 and unchanged T1rho relative to native tissue, consistent with competing effects of concentration and molecular-level changes. In addition, the heterogeneous GAG profile in these samples was not reflected in T2 or T1rho. 3) Macromolecules in an oriented matrix (mature human tissue): An oriented collagen matrix (GAG-depleted human cartilage) showed T2 and T(1rho) variation with depth consistent with 16-21% [collagen] and/or fibril orientation (magic angle effects) seen on polarized light microscopy, suggesting that both hydration and structure comprise important factors. In other human cartilage regions, T2 and T1rho abnormalities were observed unrelated to GAG or collagen orientation differences, demonstrating that hydration and/or molecular-level changes are important. Overall, these studies illustrate that T2 and T1rho are sensitive to biologically meaningful changes in cartilage. However, contrary to some previous reports, they are not specific to any one inherent tissue parameter.

Evaluation of quantitative magnetic resonance imaging, biochemical and mechanical properties of trypsin‐treated intervertebral discs under physiological compression loading

“…However, other work implies that T 1 is sensitive to biologically meaningful changes in cartilage, but is not specifically associated with any one inherent tissue parameter (35). They showed that T 1 is affected by the concentration, particularly of collagen, as well as by changes at the molecular level, and that hydration and structure also play a role (35). In the present study the small sample size may explain the lack of correlation between T 1 and proteoglycan content.…”

“…The results from this study demonstrate that T 1 can track proteoglycan content in vivo. However, other work implies that T 1 is sensitive to biologically meaningful changes in cartilage, but is not specifically associated with any one inherent tissue parameter (35). They showed that T 1 is affected by the concentration, particularly of collagen, as well as by changes at the molecular level, and that hydration and structure also play a role (35).…”

Sodium and T1ρ MRI for molecular and diagnostic imaging of articular cartilage

“…Previously, different types of multiple quantum (MQ) coherence transfer methods have been developed to characterize this interaction. However, due to an order of magnitude low SNR of MQ filtered methods, their applications have been largely limited to ex vivo studies and some imaging experiments that were performed on highly ordered tissue such as tendons (86,219). Spin-locking methods to characterize this interaction offer high SNR (comparable to single quantum coherence) and can be implemented in vivo with relative ease.…”

Multinuclear NMR and microscopic MRI studies of the articular cartilage nanostructure

“…In the inset, the same graph is presented with its y-axis drawn in a logarithmic scale. From Keinan-Adamsky et al (29) It should be mentioned that in most cases of articular cartilage imaging, the TE used to obtain T 2 maps is relatively long (usually >8 ms) (30)(31)(32)(33). This may be the reason why the bi-exponential nature of the decay curve in the deep radial zone was overlooked in most studies and T 2 values calculated in this region are relatively long.…”