1. An imaging method for the monitoring of an anatomical region during insertion of a metallic object inside the region, the method comprising: a) acquiring three-dimensional image of a specific anatomical district of the body under examination by a computed axial tomography device and storing said three-dimensional image; b) finding at least one reference point within said anatomical district; c) acquiring a two-dimensional image along a first section slice of said anatomical district passing by said at least one reference point by an ultrasound probe; d) identifying said first section plane of the acquired two-dimensional image within the stored three-dimensional image; e) constructing a first two-dimensional image with data of the three-dimensional image falling along said first section slice and corresponding to that of the acquired two-dimensional image; f) moving said ultrasound probe towards a further section slice of said anatomical district having a position and/or orientation different than that of said first section slice; g) tracking a displacement of said ultrasound probe for obtaining the image at said further section slice; h) identifying said further section slice within the stored three-dimensional image by using data related to the tracking of the displacement of said ultrasound probe; i) constructing a second two-dimensional image with data of the three-dimensional image falling along said further section slice identified at step h); j) displaying the two-dimensional image obtained at step i) and keeping in place said ultrasound probe; k) introducing a metallic object; l) acquiring a two-dimensional ecographic image along said further section slice and along which the ecographic image is reconstructed from the three dimensional data being maintained fixed and corresponding to the section plane defined by anatomical markers; and m) combining the image data from the first two-dimensional image and the second two-dimensional image with the ecographic image, wherein the contribution of the first and second two-dimensional images reconstructed from the three-dimensional data corresponds to the representation of an anatomical structure and the contribution of the ecographic image corresponds to the representation of the metallic object.