Proteoglycan-induced changes in T1ρ-relaxation of articular cartilage at 4T

Proteoglycan (PG) depletion-induced changes in T-1 rho (spin-lattice relaxation in rotating frame) relaxation and dispersion in articular cartilage were studied at 4T. Using a spin-lock cluster pre-encoded fast spin echo sequence, T-1 rho maps of healthy bovine specimens and specimens that were subjected to PG depletion were computed at varying spin-lock frequencies. Sequential PG depletion was induced by trypsinization of cartilage for varying amounts of time. Results demonstrated that over 50% depletion of PG from bovine articular cartilage resulted in average T-1 rho increases from 110-170 ms. Regression analysis of the data showed a strong correlation (R-2 = 0.987) between changes in PG and T-1 rho. T-1 rho values were highest at the superficial zone and decreased gradually in the middle zone and again showed an increasing trend in the region near the subchondral bone. The potentials of this method in detecting early degenerative changes of cartilage are discussed. Also, T-1 rho dispersion changes as a function of PG depletion are described. (C) 2001 Wiley-Liss, Inc.