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

Objective: The purpose of this study was (1) to characterize the spatial distribution of cartilage T-2 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 T-2 after 9 months. Methods: 3.0 T-MRI of the knee was performed in 8 mild OA patients and 10 age-matched controls at baseline and after 9 months. Cartilage T-2, volume, and average thickness were calculated in all patients. Texture analysis, based on the gray level co-occurrence matrix, was performed on the cartilage T-2 maps. Texture parameters, including entropy and angular second moment, were calculated at 0 degrees (corresponding to the anterior-posterior axis) and at 90 degrees (corresponding to the superior-inferior axis), with pixel offsets ranging from 1 to 3 pixels. Results: Least square means analysis showed that mean T-2 values, their standard deviation (SD), and their entropy were greater (P < 0.05) in CA patients than in controls. Over 9 months, the SD and entropy of cartilage T-2 significantly (P < 0.05) decreased in OA patients, while no significant changes were evident in cartilage thickness or volume. Conclusion: The mean cartilage T-2 values, their SD, and their entropy were greater in CA patients than in controls, indicating that the T-2 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 T-2 may precede morphological changes in thickness and volume in the progression of OA. (C) 2007 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.