Suitability of T 1Gd as the “dGEMRIC index” at 1.5T and 3.0T

Delayed gadolinium‐enhanced MRI of cartilage (dGEMRIC) is based on the theory that Gd‐DTPA 2− will distribute in inverse relation to cartilage glycosaminoglycan (GAG). T 1Gd ( T 1 after penetration of a 0.2 mmol/kg dose of Gd‐DTPA 2− ) has been used as the dGEMRIC index, although (1/ T 1Gd –1/ T 1o ) should be more representative of Gd‐DTPA 2− concentration (where T 1o = T 1 before contrast). T 1o and T 1Gd were measured in 20 volunteers at both 1.5T and 3T and the correlation between the metrics of T 1Gd and (1/ T 1Gd –1/ T 1o ) was calculated. There was a high correlation coefficient between the two metrics at both field strengths, with R = 0.94, 0.93, and 0.90 for central medial femur, posterior medial femur, and medial tibia, respectively, at 1.5T and 0.87, 0.94, 0.96 at 3T. In all cases P < 0.0001. Therefore, these data suggest that, for native cartilage, the current practice of measuring T 1Gd (but not also T 1o ) is adequate at both 1.5T and 3T. Magn Reson Med 58:830–834, 2007. © 2007 Wiley‐Liss, Inc.