Process for preparing a liquid pharmaceutical formulation containing a complex of macrocyclic chelate with a lanthanide and a mol/mol amount of free macrocyclic chelate of between 0.002% and 0.4%, said process comprising the following successive steps: b) preparation of a liquid pharmaceutical composition containing the complex of macrocyclic chelate with a lanthanide, free macrocyclic chelate that is not under the form of an excipient X[X',L] in which L is the macrocyclic chelate and X and X' are a metal ion, in particular chosen independently from calcium, sodium, zinc and magnesium, and/or free lanthanide, said step b) consisting in the preparation of a solid complex [chelate-lanthanide] and in the dissolution of the said complex in water; c) measurement in the pharmaceutical formulation obtained in step b) of the concentration of free macrocyclic chelate C ch 1 and/or of free lanthanide C lan 1; d) adjustment of C ch 1 and/or of C lan 1 by adding to the formulation obtained in step b): - if C lan 1 > 0 and/or C ch 1 < C t ch 1, free macrocyclic chelate, - if C lan 1 = 0 and C ch 1 > C t ch 1, free lanthanide, so as to obtain C ch 1 = C t ch 1 and C lan 1 = 0 with C t ch 1 representing the target concentration of the free macrocyclic chelate in the final liquid pharmaceutical formulation, C t ch 1 being selected in the range of between 0.002 % and 0.4 % mol/mol, wherein the amount of free macrocyclic chelate in the final liquid pharmaceutical formulation corresponds to the proportion of free macrocyclic chelate relative to the amount of complexed macrocyclic chelate DOTA-Gd in the final liquid pharmaceutical formulation in mol/mol, and wherein the macrocyclic chelate is DOTA and the lanthanide is gadolinium. b) preparation of a liquid pharmaceutical composition containing the complex of macrocyclic chelate with a lanthanide, free macrocyclic chelate that is not under the form of an excipient X[X',L] in which L is the macrocyclic chelate and X and X' are a metal ion, in particular chosen independently from calcium, sodium, zinc and magnesium, and/or free lanthanide, said step b) consisting in the preparation of a solid complex [chelate-lanthanide] and in the dissolution of the said complex in water; c) measurement in the pharmaceutical formulation obtained in step b) of the concentration of free macrocyclic chelate C ch 1 and/or of free lanthanide C lan 1; d) adjustment of C ch 1 and/or of C lan 1 by adding to the formulation obtained in step b): - if C lan 1 > 0 and/or C ch 1 < C t ch 1, free macrocyclic chelate, - if C lan 1 = 0 and C ch 1 > C t ch 1, free lanthanide, so as to obtain C ch 1 = C t ch 1 and C lan 1 = 0 with C t ch 1 representing the target concentration of the free macrocyclic chelate in the final liquid pharmaceutical formulation, C t ch 1 being selected in the range of between 0.002 % and 0.4 % mol/mol, wherein the amount of free macrocyclic chelate in the final liquid pharmaceutical formulation corresponds to the proportion of free macrocyclic chelate relative to the amount of complexed macrocyclic chelate DOTA-Gd in the final liquid pharmaceutical formulation in mol/mol, and wherein the macrocyclic chelate is DOTA and the lanthanide is gadolinium. - if C lan 1 > 0 and/or C ch 1 < C t ch 1, free macrocyclic chelate, - if C lan 1 = 0 and C ch 1 > C t ch 1, free lanthanide,