Multicomponent T2* mapping of knee cartilage: Technical feasibility ex vivo

Abstract

Disorganization of collagen fibers is a sign of early-stage cartilage degeneration in osteoarthritic knees. Water molecules trapped within well-organized collagen fibrils would be sensitive to collagen alterations. Multicomponent effective transverse relaxation (T2) mapping with ultrashort echo time acquisitions is here proposed to probe short T2 relaxations in those trapped water molecules. Six human tibial plateau explants were scanned on a 3T MRI scanner using a home-developed ultrashort echo time sequence with echo times optimized via Monte Carlo simulations. Time constants and component intensities of T2* decays were calculated at individual pixels, using the nonnegative least squares algorithm. Four T 2*-decay types were found: 99% of cartilage pixels having mono-, bi-, or nonexponential decay, and 1% showing triexponential decay. Short T2* was mainly in 1-6 ms, while long T2* was ∼22 ms. A map of decay types presented spatial distribution of these T 2* decays. These results showed the technical feasibility of multicomponent T2* mapping on human knee cartilage explants. © 2010 Wiley-Liss, Inc.