Single- vs. double-dose gadolinium contrast in delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) in knee osteoarthritis: is dose reduction possible on 3-T MRI?

Background Reduction in gadolinium (Gd) contrast agents is wanted due to the uncertainty of the potential side effects. Purpose To investigate whether it is possible to reduce the contrast dose from conventional double dose to single dose when increasing the field strength from 1.5-T to 3-T for separating early cartilage degeneration from healthy cartilage, assessed by delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC). Material and Methods Nine patients with knee osteoarthritis (OA), Kellgren-Lawrence grade (KLG) 1-4, were recruited from an ongoing weight loss cohort study. dGEMRIC was performed at 3-T using single (0.1 mmoI/kg) and double (0.2 mmoI/kg) doses of intravenous (i.v.) Gd-DTPA. Regions of interest (ROls) were drawn around the posterior weight-bearing femoral knee cartilage in lateral and medial compartments. In five medial compartments ROIs could not be drawn due to severe degeneration of cartilage. T1-relaxation times were compared to previously published values from 1.5-T and to non-contrast values from 3-T. Results Mean dGEMRIC T1-relaxation time in the lateral compartment was 769 ms for single dose vs. 561 ms for double dose ( P < 0.0001); and 685 ms for single dose vs. 454 ms for double dose ( P = 0.004) in the medial compartment. Conclusion We found a dose-response relationship between single and double doses of Gd-DTPA using 3-T in knee OA patients, similar to the findings at 1.5-T. Compared to the T1-relaxation time at 3-T without contrast (1240 ms), this further separation between OA and normal cartilage indicates that "single dose" dGEMRIC could be sufficient for cartilage health assessment at 3-T.