Disclosed is a metal chelate which is selected from the group, representatives including 6-N-[1,4,7-Tris(carboxylatomethyl)-1,4,7,10-tetraazacyclododecane-10-N-(pentanoyl-3-aza- 4-oxo-5-methyl-5-yl)]-2-N-(1-0-alpha-d-carbonylmethylmannopyranose)-L-Iysine-[N-methyl-(1H,1H,2H,2H,4H,4H,-3,6,9,12-tetraoxaperfluoro-hexadecyl)]-amide, Gd complex 1,4,7-Tris(carboxylatomethyl)-10-[(3-aza-4-oxo-5-methyl-5-yl)-acid N-(1H, 1H,2H,2H,4H,4H, -3,6,9,12-tetraoxaperfluoro-hexadecyl)-N-(2-methoxyethyl)amide]-1,4,7,10 tetraazacyclododecane, Gd complex and 1,4,7-Tris(carboxylatomethyl)-10-[(3-aza-4-oxo-5-methyl-5-yl)-acid N-(1H,1H,2H,2H,4H,4H,-3,6,9,12-tetraoxaperfluoro-hexadecyl)-N-(2-methoxyethyl)amide]-1,4,7,10-tetraazacyclododecane, Gd complex for use in radiotherapy.
