CHELATES OF GADOLINIUM AND DYSPROSIUM AS CONTRAST AGENTS FOR MR IMAGING

THE RECOGNITION OF the importance of magnetic materials and their effect on the relaxation times of resonating protons occurred simultaneously with the discovery of the magnetic resonance (MR) phenomenon by Bloch in 1946 (1). In early studies, paramagnetic ferric ions in solution were shown to reduce the T1 of protons in water. Solomon (2) in 1955 and Bloembergen (3) in 1957 extended this work to a variety of paramagnetic transition metals. Throughout the 1960s and 1970s, the ongoing development of paramagnetic shift reagents (4-7) and relaxation probes (8,9) contributed greatly to the development of nuclear MR spectroscopy. Paul Lauterbur was responsible for both the initial development of the MR imaging technique (10) and the early development of contrast agents. By 1978, paramagnetic ions and chelate complexes were being used to alter relaxation times in canine cardiac tissues. (11). Early animal and human MR imaging studies that used simple metal ion salts (11, 12) and chelates (13-15) as contrast agents led rapidly to the recognition that these agents could readily enhance inherently excellent MR imaging resolution. These studies also revealed the potential for coupling MR imaging with true functional or metabolic imaging.