Spatial variation of T2 in human articular cartilage.

PURPOSE To determine the spatial variation of in vivo cartilage T2 in young asymptomatic adults. MATERIALS AND METHODS Quantitative T2 maps of seven asymptomatic young male adults and one male volunteer with a history of previous intraarticular chondroid fragments were calculated by using a multiecho, spin-echo magnetic resonance imaging sequence at 3.0 T. The T2 maps were bilinearly interpolated to generate T2 profiles across the thickness of cartilage. RESULTS All seven asymptomatic volunteers demonstrated a monotonic increase in T2, which increased from 32 msec +/- 1 in the deep radial zone and 48 msec +/- 1 in the deep transitional zone to 67 msec +/- 2 in the outer transitional superficial zone. The T2 profile of the volunteer with superficial fibrillation observed at arthroscopy demonstrated marked spatial heterogeneity and a statistically significant increase in cartilage T2. CONCLUSION There is a reproducible pattern of increasing T2 that is proportional to the known spatial variation in cartilage water and is inversely proportional to the distribution of proteoglycans. The authors postulate that these regional T2 differences are secondary to the restricted mobility of cartilage water within an anisotropic solid matrix.