High resolution MRI relaxation measurements of water in the articular cartilage of the meniscectomized rat knee at 4.7 T

Measurements by magnetic resonance imaging (MRI) of the spin-spin (T-2), spin-lattice (T-1) and spin-density (M-0) parameters of water protons, optimized by using the Cramer-Rao Lower Bound (CRLB) theory, were made to quantify the effect of surgically induced osteoarthritis on rat knee cartilage at 4.7 T. Partial meniscectomy was performed on the right medial condyle of four Sprague Dawley rats, leaving the left medial condyle as a control. The animals were euthanized 3 weeks after the operation; the entire limbs were removed and T-2 and T-1 relaxation measurements and M-0 measurements of the protons of water were obtained using conventional Carr-Purcell-Meiboom-Gill (CPMG) and saturation recovery methods. M-0 was normalized with respect to a water phantom, to obtain the relative spin-density M-0%. Weight-bearing cartilage areas on the meniscectomized medial condyles exhibited a significant increase of T-2 relaxation time (P < 0.001) and of M-0% (p < 0.01) with respect to the control; T-1 relaxation times did not show any statistically significant changes. CRLB-based sampling optimization offered an insight to improved measurement precision and a reduction of scanning time against conventional sampling methods methods. Quantitative MRI assessment of the meniscectomized rat knee shows that cartilage exhibits changes in T, and M-0 values 3 weeks after operation. (C) 2004 Elsevier Inc. All rights reserved.