1. A method of measuring geometric variables of a three-dimensional structure contained in an object from at least one image (Ij) representing the object, comprising the following steps: use, by a processor, of a deformable first model (M) describing the structure, the shape of which model can be described by parameters (b), deformation, by the processor, of the first model until the first model conforms to an entirety of the structure in the image (I j ), determination, by the processor, of modified parameters (b j ) at which the first model exhibits optimum conformity with the structure, use, by the processor, of a deformable second model (M*) describing the structure, which second model in shape corresponds to the first model, and which in addition to the parameters (b) also contains at least one geometric variable, modification, by the processor, of the parameters (b) of the second model in a same manner as that of the parameters (b) of the first model, a result of such modification being modified parameters (b j ) at which the second model also exhibits optimum conformity with the structure, and derivation, by the processor, of a resultant modified geometric variable(s) after the modification of the parameters (b) of the second model.