T2 star relaxation times for assessment of articular cartilage at 3 T: a feasibility study
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T2 mapping techniques use the relaxation constant as an indirect marker of cartilage structure, and the relaxation constant has also been shown to be a sensitive parameter for cartilage evaluation. As a possible additional robust biomarker, T2* relaxation time is a potential, clinically feasible parameter for the biochemical evaluation of articular cartilage.
Materials and methods
The knees of 15 healthy volunteers and 15 patients after microfracture therapy (MFX) were evaluated with a multi-echo spin-echo T2 mapping technique and a multi-echo gradient-echo T2* mapping sequence at 3.0 Tesla MRI. Inline maps, using a log-linear least squares fitting method, were assessed with respect to the zonal dependency of T2 and T2* relaxation for the deep and superficial regions of healthy articular cartilage and cartilage repair tissue.
There was a statistically significant correlation between T2 and T2* values. Both parameters demonstrated similar spatial dependency, with longer values measured toward the articular surface for healthy articular cartilage. No spatial variation was observed for cartilage repair tissue after MFX.
Within this feasibility study, both T2 and T2* relaxation parameters demonstrated a similar response in the assessment of articular cartilage and cartilage repair tissue. The potential advantages of T2*-mapping of cartilage include faster imaging times and the opportunity for 3D acquisitions, thereby providing greater spatial resolution and complete coverage of the articular surface.
KeywordsMRI T2 T2* Knee Articular cartilage Cartilage repair
Funding for this study was provided by the project “Vienna Advanced Clinical Imaging Center” (VIACLIC), within the “Vienna Spots Of Excellence” program; a collaboration of the Medical University of Vienna and Siemens Austria.
Conflict of interest
The authors declare that there is no conflict of interest. Timothy Hughes is an employee of Siemens Healthcare, Erlangen, Germany.
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