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

Abstract

Purpose-A direct correlation between T 1ρ , 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 1ρ and T 2 values in human osteoarthritic cartilage; and to quantify the correlation between T 1ρ , T 2 , versus 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 1ρ and T 2 quantification. Nine specimens were scanned at three different orientations with respect to the B 0 : 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.Results-Both mean T 1ρ and T 2 at 54.7° were significantly higher than those measured at 90°a nd 0°, with T 1ρ showing a less increase compared to T 2 . R 1ρ (1/T 1ρ ) values had a significant, but moderate correlation with proteoglycan contents (R = 0.45, P = 0.002), while R 2 (1/T 2 ) was not correlated with proteoglycan. No significant correlation was found between relaxation times (T 1ρ or T 2 ) and collagen contents. The T 1ρ values of specimen sections with high Mankin scores were significantly higher than those with low Mankin scores (P < 0.05) © 2010 Elsevier Inc. All rights reserved.Corresponding author: Xiaojuan Li, PhD, Department of Radiology and Biomedical Imaging, University of California, San Francisco, 185 Berry Street, Suite 350, San Francisco, CA 94107, xiaojuan.li@radiology.ucsf.edu,. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Competing InterestThe authors declare that they have no competing interests. Conclusions-Quantitative MRI has a great potential to provide non-invasive imaging biomarkers for cartilage degeneration in OA. NIH Public Access

Probing articular cartilage damage and disease by quantitative magnetic resonance imaging

“…Other studies have shown only a moderate correlation with proteoglycan content with no correlation with collagen content [55] nor water content [108]. Additionally, a recent study found that T 1r and GAG content can be correlated in the deeper zones but not in the upper half of cartilage [109].…”

“…Additionally, studies have shown that T 1r tends to reflect depth-dependent trends in T 2 [33], with the highest T 1r values at the superficial tangential zone and decreasing values reaching a minimum at either the middle zone [28,51] or the deep zone [33,110]. Although the exact relationship of T 1r to proteoglycan or other biochemical content in articular cartilage remains unclear [55,107], T 1r mapping is gaining momentum as a viable technique for imaging of cartilage biochemistry.…”

Principal component analysis-T1ρ voxel based relaxometry of the articular cartilage: a comparison of biochemical patterns in osteoarthritis and anterior cruciate ligament subjects

“…While T 2 relaxation times is primarily affected by hydration and collagen structure due to dipolar interactions (5), the spin-lock techniques used in T 1ρ reduce dipolar interactions (6). Chemical exchange on proteoglycan and water protons was suggested to contribute to T 1ρ in cartilage, although T 1ρ changes in cartilage may be affected by hydration and collagen structure as well (7). T 1ρ quantification was adopted in previous study to detect early signs of OA (8)(9)(10).…”

Are There Sex Differences in Knee Cartilage Composition and Walking Mechanics in Healthy and Osteoarthritis Populations?

“…Quantitative MRI techniques, however, including T 1q relaxation time mapping, enable the assessment of cartilage composition noninvasively and are useful to visualize the loss of collagen matrix that occurs early in the OA disease process [1,33,44,45]. An increase in T 1q relaxation times indicates loss of proteoglycans and possibly a concomitant increase in hydration [1,33,34,38]. T 1q relaxation times have been shown to detect early knee cartilage degeneration in multiple studies [33,49,53,55].…”