Quantitative MRI using T1ρ, and T2 in human osteoarthritic cartilage specimens: correlation with biochemical measurements and histology

Purpose: A direct correlation between T-1 rho, T-2 and quantified proteoglycan and collagen contents in human osteoarthritic cartilage has yet to be documented. We aimed to investigate the orientation effect on T-1 rho and T-2 values in human osteoarthritic cartilage and to quantify the correlation between T-1 rho, T-2 vs. biochemical composition and histology in human osteoarthritic cartilage. Materials and methods: Thirty-three cartilage specimens were collected from patients who underwent total knee arthroplasty due to severe osteoarthritis and scanned with a 3T MR scanner for T-1 rho and T-2 quantification. Nine specimens were scanned at three different orientations with respect to the B-0: 0 degrees, 90 degrees and 54.7 degrees. Core punches were taken after MRI. Collagen and proteoglycan contents were quantified using biochemical assays. Histology sections were graded using Mankin scores. The correlation between imaging parameters, biochemical contents and histological scores were studied. Results: Both mean T-1 rho and T-2 at 54.7 degrees were significantly higher than those measured at 90 degrees and 0 degrees, with T-1 rho showing less increase compared to T-1 rho. R-1 rho (1/T-1 rho) values had a significant but moderate correlation with proteoglycan contents (R=.45, P=.002), while R-2 (1/T-2) was not correlated with proteoglycan. No significant correlation was found between relaxation times (T-1 rho and T-2) and collagen contents. The T-1 rho values of specimen sections with high Mankin scores were significantly higher than those with low Mankin scores (P<.05). Conclusions: Quantitative MRI has a great potential to provide noninvasive imaging biomarkers for cartilage degeneration in osteoarthritis. (C) 2011 Elsevier Inc. All rights reserved.