Factors affecting paramagnetic contrast enhancement in synovial fluid: effects of electrolytes, protein concentrations, and temperature on water proton relaxivities from Mn ions and Gd chelated contrast agents

Introduction: Protein and electrolyte concentration of synovial fluid (SF) varies with the type of underlying arthritis. These characteristics can be utilized by magnetic resonance technology to provide a potentially significant diagnostic modality through quantitative assessments of inherent water relaxation rates and their response to contrast agents. Methods: We evaluated the effect of a classic " in vitro" contrast agent, the Mn ion, and a common " in vivo" gadolinium based contrast agent, gadopentetate dimeglumine, on the water relaxation times of solutions with biochemical compositions simulating different types of arthritis along with similar studies of SF obtained from patients. Results: The results demonstrate how protein and electrolyte concentrations play a significant role in the response of water relaxation to the Mn ion but much less so to chelated gadolinium contrast agents used clinically. Discussion: A major challenge remains to develop paramagnetic agents with less toxicity than the Mn ion but with similar properties that can then serve as a tool to determine protein concentrations through imaging and thereby assist in the diagnosis of inflammatory arthrides and evaluation of therapeutic regimens.