Imaging Markers for Early Matrix Depletion

Sharmila Majumdar¹

Articular cartilage is composed of chondrocytes surrounded by a large extracellular matrix (ECM) composed of water and two groups of macromolecules: proteoglycan (PG) and collagen fibers. ECM changes are said to precede morphological changes in articular cartilage and may prove to be early biomarkers of osteoarthritis. In MRI, these macromolecules restrict motion of water protons, affecting relaxation times and contrast agent uptake. ECM changes such as PG loss, as reflected in measurements of: 1) T1ρ of water protons, 2) Delayed Gadolinium-enhanced MRI of cartilage (dGEMRIC) and collagen content and orientation changes probed using T2 relaxation time measures will be discussed.