Imaging biomarker with T1ρ and T2 mappings in osteoarthritis – In vivo human articular cartilage study

Is T1ρ Mapping an Alternative to Delayed Gadolinium-enhanced MR Imaging of Cartilage in the Assessment of Sulphated Glycosaminoglycan Content in Human Osteoarthritic Knees? An in Vivo Validation Study

“…Our results, however, are more consistent with those from one of the two previous in vivo validation studies of T1r mapping, which showed only a weak correlation (r = 0.44) between T1r relaxation times and sGAG content in the lateral tibial plateau cartilage of 20 patients with osteoarthritis (14). A possible explanation for the difference in the strength of reported correlation values between in vivo and in vitro or ex vivo acquired T1r maps and cartilage sGAG content may be the differences in specific acquisition parameters.…”

“…Optimization of these parameters might improve the ability of T1r mapping to help assess cartilage sGAG content but will likely increase the acquisition time. Moreover, the spin-lock frequency was usually higher in vitro and ex vivo (8,10) compared with in vivo (14,15). A higher spin-lock frequency causes less B0 inhomogeneity, which may improve the accuracy of T1r mapping; however, increased spin-lock frequency is a limiting factor sGAG content measured with highperformance liquid chromatography in nine cartilage explants.…”

“…A possible explanation for the difference in the strength of reported correlation values between in vivo and in vitro or ex vivo acquired T1r maps and cartilage sGAG content may be the differences in specific acquisition parameters. For example, the number and duration of spin-lock times, field of view, and in-plane image matrix are usually different for in vitro or ex vivo experiments (9-11) compared with in vivo experiments (7,14,15). Optimization of these parameters might improve the ability of T1r mapping to help assess cartilage sGAG content but will likely increase the acquisition time.…”

“…In vivo validation was performed in only one study of dGEM-RIC (13) and only two studies of T1r mapping (14,15). Furthermore, to our knowledge, no investigators have applied both imaging biomarkers in humans in vivo and compared the outcomes with a standard of reference for cartilage sGAG content to validate and Abbreviations: BMI = body mass index CI = credibility interval dGEMRIC = delayed gadolinium-enhanced MR imaging of cartilage ROI = region of interest sGAG = sulphated glycosaminoglycan SPGR = spoiled gradient echo 3D = three-dimensional…”

Articular Cartilage of the Human Knee Joint: In Vivo Multicomponent T2 Analysis at 3.0 T

“…The T2 of cartilage is one of the most commonly used MR imaging parameters and has been shown to be sensitive for detection of cartilage degeneration in ex vivo specimens (7) and human subjects (8)(9)(10)(11)(12). However, cartilage T2 is a complex measurement that is influenced by multiple factors including water and macromolecular content (13)(14)(15)(16), organization of the collagen fiber network (17)(18)(19), cartilage loading (20)(21)(22), and orientation of cartilage relative to the main magnetic field (23). Thus, changes in cartilage T2 may be difficult to interpret and sometimes challenging to detect because of the multiple potentially competing biologic factors that influence the measurement.…”