Investigation of apparent diffusion constant as an indicator of early degenerative disease in articular cartilage

Abstract

Purpose To investigate the apparent diffusion constant (ADC) as a prospective magnetic resonance imaging (MRI) marker of early degeneration in articular cartilage. Materials and Methods Early degenerative changes were studied using in vitro MRI on cartilage‐bone specimens excised from human femoral condyles. The loss of proteoglycans developed in vivo due to a degenerative process was compared with a gadolinium diethylenetriamine pentaacetate anion (Gd‐DTPA^2–) enhanced decrease of T₁ relaxation times, and with an increase of ADCs and T₂ relaxation times. Results Contrast enhanced T₁ values decreased and the diffusion constants increased in cartilage regions with depleted proteoglycans. The relative changes in diffusion constants were smaller than those of Gd‐DTPA^2– enhanced T₁, and in some proteoglycan‐depleted regions no changes in the diffusion constants were detected. T₂ relaxation times showed considerable spatial variability that did not correlate with proteoglycan concentration. Conclusion In contrast to Gd‐DTPA^2– enhanced T₁, which reflects changes in chemical composition, diffusion constants may reflect structural degradation of the cartilage matrix. J. Magn. Reson. Imaging 2003;17:440–444.