Process for the planning, preparation, supervision, monitoring and/or final control of a surgical intervention in the human or animal body in order to insert at least one implant, in which process at least two in each case multidimensional representations (4, 12, 13) of at least one section of the body are displayed with the aid of an image assistance device, of which at least two representations differ with respect to the number of dimensions of the representations, wherein in a first step, the planner/surgeon selects a plurality of different multidimensional patient images, in particular 2-D and/or 3-D patient images (41, 42), from an external image source, which patient images are made available to the image assistance device, in a second step, volume patient images are each segmented with the aid of the image assistance device, wherein the multidimensional representations (12, 13) are recognized and processed before, during or after their representation with the aid of the image assistance device, and in a third step, it is made possible to assign bones which are displayed in the 2-D and 3-D patient images, respectively, to the 2-D and 3-D patient images, respectively, in a positionally correct manner by means of a fixed coordinate reference between the 2-D image data and the 3-D image data, wherein the same coordinates in the 2-D and/or 3-D patient images are simultaneously displayed in different screen windows, and in a fourth step, the planner/surgeon selects at least one 2-D and/or 3-D representation (12, 13) as a representation in at least one screen window of the screen of the image assistance device as a working representation which is used to continue the preoperative planning, in a fifth step, the planner/surgeon carries out further planning measures, in particular for simulating a surgical intervention to be planned, with the aid of the image assistance device in at least one representation, wherein information and/or data on implants (2, 46) and/or 2-D and/or 3-D representations (12, 13) of implants are made available to the image assistance device, and wherein at least one patient image (12, 13) is recognized and processed before, during or after its representation with the aid of an image assistance device in a working representation, and wherein the at least one multidimensional representation can be compared with a reference model, and wherein the 2-D and 3-D patient images (12, 13) are assigned to one another, and wherein all steps of a surgical intervention to be planned can be simulated in each of the representations and/or the 3-D or 2-D representation (12, 13), and wherein the obtained planning data can be transferred via an interface to a mobile or stationary surgical navigation system or an image assistance device, wherein the image assistance device with an interface transfers online data during the surgical intervention to display, auxiliary, measuring and imaging recording devices, and wherein reference data, target values, standard values and/or general patient-unspecific data and/or information on implants are made available to the image assistance device for the planning, supervision, monitoring and/or final control of a surgical intervention, which are matched with standard values before they are made available.