Cartilage Compositional T ₂ Patterns in Subjects at Risk of Polyarticular OA: Technical Feasibility at 0.55 T, Clinical and Functional Associations

ABSTRACT The feasibility of rapid, state‐of‐the‐art, and quantitative T 2 ‐mapping at low field (0.55 T) MRI compared to 3.0 T and its associations with clinical and functional performance remain a crucial yet underexplored piece. A phantom of falcon tubes with three varying agarose solutions (2%, 3%, and 4%) was scanned at a 3.0‐ and 0.55‐T scanner. Two cohorts of seven healthy controls and 10 early‐to‐moderate hip osteoarthritis (OA) subjects (with no clinical symptoms of knee OA) underwent two consecutive bilateral MRI scans on a 3.0‐ and a 0.55‐T scanner with an hour of rest in between. T 2 relaxation values were autoextracted from six cartilage subcompartments. WORMS Cartilage‐lesion scoring was performed to characterize knee cartilage subcompartments with having cartilage defects or not. Patient‐reported outcome scores were collected along with physical functional tests for the hip OA subjects. Statistical tests are as follows: Shapiro–Wilk test, unpaired t ‐tests, Pearson, and Spearman ( ρ ) correlations. Significance was set at p < 0.05. Percent increases in T 2 values were noted from 3.0 to 0.55 T. For compartments with cartilage defects, T 2 values at both 0.55 and 3.0 T were significantly higher for hip OA subjects than healthy controls. For compartments with no cartilage defects, only at 0.55 T did hip OA subjects have significantly elevated T 2 values compared to the healthy controls, not at 3.0 T. Significant correlations were noted between T 2 values of knee compartments with age, patient‐reported outcomes, and functional tests at 0.55 and 3.0 T. This is one of the first studies to explore the feasibility of the Radial‐TSE‐T 2 mapping approach at 0.55 T for reporting a baseline set of compositional values of knee cartilages. The increase in T 2 values from 3.0 to 0.55 T is utilized for detecting early T 2 elevation of the cartilage compartments of subjects at a higher risk of OA, compared to healthy controls. The study also reports novel baseline associations between T 2 properties at 0.55 T, clinical and functional parameters, compared to 3.0 T.