Orientation anisotropy of quantitative MRI parameters in degenerated human articular cartilage

Abstract

Quantitative magnetic resonance (MR) relaxation parameters demonstrate varying sensitivity to the orientation of the ordered tissues in the magnetic field. In this study, the orientation dependence of multiple relaxation parameters was assessed in cadaveric human cartilage with varying degree of natural degeneration, and compared with biomechanical testing, histological scoring, and quantitative histology. Twelve patellar cartilage samples were imaged at 9.4 T MRI with multiple relaxation parameters, including T 1 , T 2 , CW − T 1ρ , and adiabatic T 1ρ , at three different orientations with respect to the main magnetic field. Anisotropy of the relaxation parameters was quantified, and the results were compared with the reference measurements and between samples of different histological Osteoarthritis Research Society International (OARSI) grades. T 2 and CW − T 1ρ at 400 Hz spin-lock demonstrated the clearest anisotropy patterns. Radial zone anisotropy for T 2 was significantly higher for samples with OARSI grade 2 than for grade 4. The proteoglycan content (measured as optical density) correlated with the radial zone MRI orientation anisotropy for T 2 (r = 0.818) and CW − T 1ρ with 400 Hz spin-lock (r = 0.650). Orientation anisotropy of MRI parameters altered with progressing cartilage degeneration. This is associated with differences in the integrity of the collagen fiber network, but it also seems to be related to the proteoglycan content of the cartilage. Samples with advanced OA had great variation in all biomechanical and histological properties and exhibited more variation in MRI orientation anisotropy than the less degenerated samples. Understanding the background of relaxation anisotropy on a molecular level would help to develop new MRI contrasts and improve the application of previously established quantitative relaxation contrasts.

The relation between the biochemical composition of knee articular cartilage and quantitative MRI: a systematic review and meta-analysis

“…For 400Hz T1ρ, Hänninen et al (2021) reported no significant correlations between PLM retardation (r=0.07, p=0.83) or PLM anisotropy (r=0.20, p=0.53) 26 . The correlation between with PLM angle was also non-significant (rho=-0.517, p=0.089).…”

“…T2 mapping was studied in relation to PLM in 5 studies (table 2). The relation between T2 mapping and PLM retardation ranged between non-existent (rho=-0.09, p=0.78 26 ) and strong (r=-0.88 41 ). For anisotropy, correlations ranged from rho=0.287, p=0.366) to r=0.87 26,41 .…”

“…Correlations between T1 mapping and PLM were reported in three studies 26,33,41 . Correlations with PLM retardation, anisotropy and angle reported by Hänninen et al (2021) 26 did not reach significance. Rautiainen et al did also not find a significant correlation with anisotropy (r=-0.27, p>0.05).…”

Establishing an in vitro model of MR-T1ρ imaging technology to quantify nucleus pulposus tissue proteoglycans: a preliminary study

“…In addition, some scholars have found that when studying degeneration of the lumbar intervertebral disc in humans and cadavers, MR-T1ρ imaging is more sensitive than MR-T2WI imaging in the early degeneration of the lumbar intervertebral disc (5). The proteoglycan concentration in the lumbar intervertebral disc nucleus pulposus tissue has been analyzed in many studies, which have found that the proteoglycan concentration has a good and positive correlation with the T1ρ relaxation time value (6)(7)(8).…”

Quantitative susceptibility mapping of articular cartilage: Ex vivo findings at multiple orientations and following different degradation treatments

“…The aim of this study was to find reliable methods for ex vivo QSM of articular cartilage and to investigate the sensitivity of QSM to different degradation treatments of articular cartilage. Acknowledging the known orientation dependence of several MRI parameters (including QSM) in cartilage, we also investigated the anisotropy of the susceptibility . Because the primary aims of this study were to evaluate methodological aspects as well as the sensitivity of QSM to variations in cartilage properties and constituents, the sample group was chosen to be broad in terms of cartilage degradations, although not very large in size.…”