Gadolinium-labeled liposomes: targeted MR contrast agents for the liver and spleen.

A contrast agent for use in magnetic resonance (MR) imaging of the liver and spleen has been designed in which gadolinium-DTPA is chemically incorporated into the lamellar phase of liposome particles. This agent has excellent in vivo stability and is taken up by liver and spleen of normal mice after intravenous administration. The T1 increased by 110% in liver and 66% in spleen at 4 degrees C. At 37 degrees, the relaxation rate in the liver increased by 180%. This method is an attractive concept for the development of various organ-specific liposomal contrast agents that may be used for either MR imaging or nuclear medicine.