Advantages of an increased dose of MRI contrast agent for enhancing inflammatory synovium

MRI intravenous contrast enhancement of inflammatory synovium has been studied at two different doses to determine to what extent enhancement is dose dependent. 19 patients with clinically active rheumatoid arthritis involving a knee were scanned twice, one week apart, using 0.1 mmol/kg of gadoteridol (ProHance) on the first occasion and 0.3 mmol/kg on the second. Static pre-and post-contrast images together with dynamic images immediately following injection were obtained on a 1.0T scanner. On subjective assessment, 84% of patients showed improved enhancement. 47% showed more enhancing tissue, a clearer delineation of enhancing tissue or both. Objectively, enhancement was increased significantly at the higher dose, as judged by the percentage increase in mean signal intensity within regions of interest plotted over the suprapatellar pouch (1723% v. 1005% enhancement P < 0.05). In practical terms the better visualization of enhancing tissue achieved with higher doses is likely to reduce margins of error in attempts at quantification from MRI scans, particularly of synovial volume, but emphasizes also the need for care and consistency to be exercised in calculating the exact dose of contrast medium to be administered.