T1ρ Dispersion in Articular Cartilage: Relationship to Material Properties and Macromolecular Content

Kathryn E Keenan; Thor F Besier; John M Pauly; R Lane Smith; Scott L Delp; Gary S Beaupre; Garry E Gold

doi:10.1177/1947603515569529

T1ρ Dispersion in Articular Cartilage: Relationship to Material Properties and Macromolecular Content

Cartilage. 2015 Apr;6(2):113-22. doi: 10.1177/1947603515569529.

Authors

Kathryn E Keenan¹, Thor F Besier², John M Pauly³, R Lane Smith⁴, Scott L Delp⁵, Gary S Beaupre⁶, Garry E Gold⁷

Affiliations

¹ Department of Mechanical Engineering, Stanford University, Stanford, CA, USA.
² Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand.
³ Magnetic Resonance Systems Research Laboratory, Department of Electrical Engineering, Stanford University, Stanford, CA, USA.
⁴ Department of Orthopaedic Surgery, Stanford University, Stanford, CA, USA ; Rehabilitation R&D Musculoskeletal Research Laboratory, Department of Veterans Affairs, Palo Alto, CA, USA.
⁵ Department of Mechanical Engineering, Stanford University, Stanford, CA, USA ; Department of Bioengineering, Stanford University, Stanford, CA, USA.
⁶ Rehabilitation R&D Musculoskeletal Research Laboratory, Department of Veterans Affairs, Palo Alto, CA, USA.
⁷ Department of Orthopaedic Surgery, Stanford University, Stanford, CA, USA ; Department of Bioengineering, Stanford University, Stanford, CA, USA ; Department of Radiology, Stanford University, Stanford, CA, USA.

Abstract

Objective: This study assessed T1ρ relaxation dispersion, measured by magnetic resonance imaging (MRI), as a tool to noninvasively evaluate cartilage material and biochemical properties. The specific objective was to answer two questions: (1) does cartilage initial elastic modulus (E 0) correlate with T1ρ dispersion effects and (2) does collagen or proteoglycan content correlate with T1ρ dispersion effects?

Design: Cadaveric patellae with and without visible cartilage damage on conventional MR were included. T2 and T1ρ relaxation times at 500 and 1000 Hz spin-lock field amplitudes were measured. We estimated T1ρ dispersion effects by measuring T1ρ relaxation time at 500 and 1000 Hz and T2 relaxation time and using a new tool, the ratio T1ρ/T2. Cartilage initial elastic modulus, E 0, was measured from initial response of mechanical indentation creep tests. Collagen and proteoglycan contents were measured at the indentation test sites; proteoglycan content was measured by their covalently linked sulfated glycosaminoglycans (sGAG). Pearson correlation coefficients were determined, taking into account the clustering of multiple samples within a single patella specimen.

Results: Cartilage initial elastic modulus, E 0, increased with decreasing values of T1ρ/T2 measurements at both 500 Hz (P = 0.034) and 1000 Hz (P = 0.022). 1/T1ρ relaxation time (500 Hz) increased with increasing sGAG content (P = 0.041).

Conclusions: T1ρ/T2 ratio, a new tool, and cartilage initial elastic modulus are both measures of water-protein interactions, are dependent on the cartilage structure, and were correlated in this study.

Keywords: T1ρ dispersion; articular cartilage; collagen; initial elastic modulus; proteoglycan.

Abstract

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