Longitudinal study using voxel-based relaxometry: Association between cartilage T 1ρ and T 2 and patient reported outcome changes in hip osteoarthritis.

PURPOSE: To study the local distribution of hip cartilage T1ρ and T2 relaxation times and their association with changes in patient reported outcome measures (PROMs) using a fully automatic, local, and unbiased method in subjects with and without hip osteoarthritis (OA).

MATERIALS AND METHODS: The 3 Tesla MRI studies of the hip were obtained for 37 healthy controls and 16 subjects with radiographic hip OA. The imaging protocol included a three-dimensional (3D) SPGR sequence and a combined 3D T1ρ and T2 sequence. Quantitative cartilage analysis was compared between a traditional region of interest (ROI)-based method and a fully automatic voxel-based relaxometry (VBR) method. Additionally, VBR was used to assess local T1ρ and T2 differences between subjects with and without OA, and to evaluate the association between T1ρ and T2 and 18-month changes PROMs.

RESULTS: Results for the two methods were consistent in the acetabular (R = 0.79; coefficients of variation [CV] = 2.9%) and femoral cartilage (R = 0.90; CV = 2.6%). VBR revealed local patterns of T1ρ and T2 elevation in OA subjects, particularly in the posterosuperior acetabular cartilage (T1ρ : P = 0.02; T2 : P = 0.038). Overall, higher T1ρ and T2 values at baseline, particularly in the anterosuperior acetabular cartilage (T1ρ : Rho = -0.42; P = 0.002; T2 : Rho = -0.44; P = 0.002), were associated with worsening PROMS at 18-month follow-up.

CONCLUSION: VBR is an accurate and robust method for quantitative MRI analysis in hip cartilage. VBR showed the capability to detect local variations in T1ρ and T2 values in subjects with and without osteoarthritis, and voxel based correlations demonstrated a regional dependence between baseline T1ρ and T2 values and changes in PROMs.

LEVEL OF EVIDENCE: 1 J. MAGN. RESON. IMAGING 2017;45:1523-1533.