Longitudinal evaluation of T1ρ and T2 spatial distribution in osteoarthritic and healthy medial knee cartilage

Summary Objective To investigate longitudinal changes in laminar and spatial distribution of knee articular cartilage magnetic resonance imaging (MRI) T 1ρ and T 2 relaxation times, in individuals with and without medial compartment cartilage defects. Design All subjects (at baseline n  = 88, >18 years old) underwent 3-Tesla knee MRI at baseline and annually thereafter for 3 years. The MR studies were evaluated for presence of cartilage defects (modified Whole-Organ Magnetic Resonance Imaging Scoring – mWORMS), and quantitative T 1ρ and T 2 relaxation time maps. Subjects were segregated into those with (mWORMS ≥2) and without (mWORMS ≤1) cartilage lesions at the medial tibia (MT) or medial femur (MF) at each time point. Laminar (bone and articular layer) and spatial (gray level co-occurrence matrix – GLCM) distribution of the T 1ρ and T 2 relaxation time maps were calculated. Linear regression models (cross-sectional) and Generalized Estimating Equations (GEEs) (longitudinal) were used. Results Global T 1ρ , global T 2 and articular layer T 2 relaxation times at the MF, and global and articular layer T 2 relaxation times at the MT, were higher in subjects with cartilage lesions compared to those without lesions. At the MT global T 1ρ relaxation times were higher at each time point in subjects with lesions. MT T 1ρ and T 2 became progressively more heterogeneous than control compartments over the course of the study. Conclusion Spatial distribution of T 1ρ and T 2 relaxation time maps in medial knee OA using GLCM technique may be a sensitive indicator of cartilage deterioration, in addition to whole-compartment relaxation time data.