Segmented chelating polymers as imaging and therapeutic agents

A composition suitable for use in diagnostic imaging or as a cell killing agent comprising a chelating residue linked via an amide linkage to a poly(alkylene oxide) moiety, said compisition having a molecular weight of at least 4,500; wherein: Z is a chelating residue; Q is a divalent poly(alkylene oxidylene) moiety having a carbon terminus at R and at L; L represents an amide linkage; E(b) is one or more counterions each having a charge of b; b is an integer from 1, 2 and 3; n is an integer selected from the group 1, 2, 3 and 4; w is zero or an integer from 1 to 5; M(+a) is a cation, having a charge of +a; a is an integer from 1 to 4; r is 0 or an integer from 1 to 3, provided that when r is 2-3, each M(+a) can be the same or different cation; d is the total charge on the chelating residue and is an integer from 0 to 10; d+ SIGMA (bxw)+ SIGMA (axr)=O; and R is a capping moiety chosen from the group consisting of hydrogen, hydroxyl, C1-C4 alkyl, aryl containing 6 to 24 carbon atoms, C2-C5 alkanoyloxyl and C1-C4 alkoxy, or R is an immunoreactive group or cytotoxic drug linked to Q by a chemical bond or a linking group.