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 enhancemen t is dose dependent. 19 patients with clinically active rheumatoid art hritis involving a knee were scanned twice, one week apart, using 0.1 mmol/kg of gadoteridol (ProHance(R)) on the first occasion and 0.3 mmo l/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 en hancement, 47% showed more enhancing tissue, a clearer delineation of enhancing tissue or both. Objectively, enhancement was increased signi ficantly at the higher dose, as judged by the percentage increase in m ean signal intensity within regions of interest plotted over the supra patellar pouch (1723% v. 1005% enhancement P < 0.05). In practical ter ms the better visualization of enhancing tissue achieved with higher d oses is likely to reduce margins of error in attempts at quantificatio n 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.