The present invention relates to diethylenetriamine pentaacetic acid (DTPA) derivates and metal complexes thereof, and radiation sources and contrast agents including the metal complexes. More particularly, the present invention relates to DTPA derivatives, which contain iodine and are useful as contrast agents for diagnosing renal function, metal complexes of the DTPA derivatives with 99m Tc, 166 Ho, 111 In, 90 Y, 153 Sm, 186 Re, 188 Re, 68 Ga, or 177 Lu, which are useful as liquid radiation sources for treating vascular stenosis and contrast agents for diagnosing renal function, and radiation sources and contrast agents including the metal complexes. The DTPA derivatives and metal complexes thereof are safe because the metal complexes are excreted via the kidneys and bladder within several minutes from the time of use as liquid radiation sources for treating vascular stenosis, and are cost-effective because they are potentially useful as contrast agents and as agents for diagnosing renal function.
