T2 of articular cartilage in the presence of Gd-DTPA2-.

T(2) information and delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) are both used to characterize articular cartilage. They are currently obtained in separate studies because Gd-DTPA(2-) (which is needed for dGEMRIC) affects the inherent T(2) information. In this study, T(2) was simulated and then measured at 8.45 T in 20 sections from two human osteochondral samples equilibrated with and without Gd-DTPA(2-). Both the simulations and data demonstrated that Gd-DTPA(2-) provides a non-negligible mechanism for relaxation, especially with higher (1 mM) equilibrating Gd-DTPA(2-) concentrations, and in areas of tissue with high T(2) (due to weak inherent T(2) mechanisms) and high tissue Gd-DTPA(2-) (due to a low glycosaminoglycan concentration). Nonetheless, T(2)-weighted images of cartilage equilibrated in 1 mM Gd-DTPA(2-) showed similar T(2) contrast with and without Gd-DTPA(2-), demonstrating that the impact on T(2) was not great enough to affect identification of T(2) lesions. However, T(2) maps of the same samples showed loss of conspicuity of T(2) abnormalities. We back-calculated inherent T(2)'s (T(2,bc)) using a T(2)-relaxivity value from a 20% protein phantom (r(2) = 9.27 +/- 0.09 mM(-1)s(-1)) and the Gd-DTPA(2-) concentration calculated from T(1,Gd). The back-calculation restored the inherent T(2) conspicuity, and a correlation between T(2) and T(2,bc) of r = 0.934 (P < 0.0001) was found for 80 regions of interest (ROIs) in the sections. Back-calculation of T(2) is therefore a viable technique for obtaining T(2) maps at high equilibrating Gd-DTPA(2-) concentrations. With T(2)-weighted images and/or low equilibrating Gd-DTPA(2-) concentrations, it may be feasible to obtain both T(2) and dGEMRIC information in the presence of Gd-DTPA(2-) without such corrections. These conditions can be designed into ex vivo studies of cartilage. They appear to be applicable for clinical T(2) studies, since pilot clinical data at 1.5 T from three volunteers demonstrated that calculated T(2) maps are comparable before and after "double dose" Gd-DTPA(2-) (as utilized in clinical dGEMRIC studies). Therefore, it may be possible to perform a comprehensive clinical examination of dGEMRIC, T(2), and cartilage volume in one scanning session without T(2) data correction.