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

Abstract

PurposeA direct correlation between T1ρ, T2 and quantified proteoglycan and collagen contents in human osteoarthritic cartilage has yet to be documented. We aimed to investigate the orientation effect on T1ρ and T2 values in human osteoarthritic cartilage and to quantify the correlation between T1ρ, T2 vs. biochemical composition and histology in human osteoarthritic cartilage. Materials and methodsThirty-three cartilage specimens were collected from patients who underwent total knee arthroplasty due to severe osteoarthritis and scanned with a 3T MR scanner for T1ρ and T2 quantification. Nine specimens were scanned at three different orientations with respect to the B0: 0°, 90° and 54.7°. 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. ResultsBoth mean T1ρ and T2 at 54.7° were significantly higher than those measured at 90° and 0°, with T1ρ showing less increase compared to T2. R1ρ (1/T1ρ) values had a significant but moderate correlation with proteoglycan contents (R=.45, P=.002), while R2 (1/T2) was not correlated with proteoglycan. No significant correlation was found between relaxation times (T1ρ or T2) and collagen contents. The T1ρ values of specimen sections with high Mankin scores were significantly higher than those with low Mankin scores (P<.05). ConclusionsQuantitative MRI has a great potential to provide noninvasive imaging biomarkers for cartilage degeneration in osteoarthritis.