Quantitative MRI Analysis of Menisci Using Biexponential T2* Fitting with a Variable Echo Time Sequence

PurposeThe goal of this study was to differentiate between normal, degenerative meniscus, and meniscal tears using monoexponentially and biexponentially calculated T-2*. Meniscal disease, characterized by an altered collagen fiber matrix, might be detectable in vivo using quantitative T-2* mapping. MethodsA 3D Cartesian spoiled gradient echo technique was adapted to enable the use of a variable echo time approach in combination with a highly asymmetric readout. T-2* was calculated monoexponentially and biexponentially using three- and five-parametric non-linear fits, respectively. ResultsFrom a total of 68 evaluated menisci, 48 were normal, 12 were degenerated, and eight had tears. Mean values for the short (T-2*(s)) and long (T-2*(l)) T-2* components were as follows: in normal menisci, 0.820.38/15.0 +/- 5.4 ms, respectively; in degenerated menisci, 1.29 +/- 0.53/19.97 +/- 5.59 ms, respectively; and, in meniscal tears, 2.05 +/- 0.73 and 26.83 +/- 7.72 ms, respectively. Biexponentially fitted T-2* demonstrated a greater ability to distinguish normal and degenerated menisci using receiver operating characteristic (ROC) analysis (higher area under curve as well as higher specificity and sensitivity). ConclusionThis study suggests that biexponential fitting, used for T-2* calculation in the menisci, provides better results compared to monoexponential fitting. Observed changes in T-2* result from the matrix reorganization in degenerative processes in the menisci, which affects the collagen fiber orientation, as well as content. Magn Reson Med 71:1015-1023, 2014. (c) 2013 Wiley Periodicals, Inc.