The feasibility of characterizing the spatial distribution of cartilage T2 using texture analysis 1

SummaryObjectiveThe purpose of this study was (1) to characterize the spatial distribution of cartilage T2 in postmenopausal osteoarthritis (OA) patients and age-matched healthy subjects using second order texture measures at baseline, and (2) to analyze changes in the texture of cartilage T2 after 9 months.Methods3.0 T-MRI of the knee was performed in 8 mild OA patients and 10 age-matched controls at baseline and after 9 months. Cartilage T2, volume, and average thickness were calculated in all patients. Texture analysis, based on the gray level co-occurrence matrix, was performed on the cartilage T2 maps. Texture parameters, including entropy and angular second moment, were calculated at 0° (corresponding to the anterior–posterior axis) and at 90° (corresponding to the superior–inferior axis), with pixel offsets ranging from 1 to 3 pixels.ResultsLeast square means analysis showed that mean T2 values, their standard deviation (SD), and their entropy were greater (P < 0.05) in OA patients than in controls. Over 9 months, the SD and entropy of cartilage T2 significantly (P < 0.05) decreased in OA patients, while no significant changes were evident in cartilage thickness or volume.ConclusionThe mean cartilage T2 values, their SD, and their entropy were greater in OA patients than in controls, indicating that the T2 values in osteoarthritic cartilage are not only elevated, but also more heterogeneous than those in healthy cartilage. The longitudinal results demonstrate that changes in texture parameters of cartilage T2 may precede morphological changes in thickness and volume in the progression of OA.