System for helping to guide an endovascular tool in vascular structures, comprising an imaging device able to acquire two-dimensional images of portions of the body of a patient, a programmable device and a viewing unit, said system being characterised in that it is adapted for: - during an initial planning phase (P 1), - - obtaining and memorising a preoperative three-dimensional image comprising a target vascular structure of a patient, - - determining a first three-dimensional anatomical model (M 1) specific to the patient from the three-dimensional image acquired, this first three-dimensional anatomical model (M 1) being located in the same spatial reference as the three-dimensional image, - during an intervention phase (P 2), - - acquiring one or several perioperative two-dimensional images comprising the target vascular structure of the patient, opacified or not, - - estimating a rigid transformation between the preoperative three-dimensional image and the perioperative two-dimensional images, said system being characterised in that it is further adapted for: - - estimating an elastic transformation between said three-dimensional image and the two-dimensional images according to the rigid transformation and a simulation of vascular deformations induced by introducing the tool into the target vascular structure, said simulation being obtained as a function of a local state of the target vascular structure, a relationship between the target vascular structure and its direct environment, and mechanical properties of the endovascular tool, - - applying a combination of the rigid transformation and of the elastic transformation to the first three-dimensional anatomical model (M 1) specific to the patient in order to obtain a second three-dimensional model (M 2) specific to the patient, - - displaying on the viewing unit said second three-dimensional model specific to the patient in superposition on the two-dimensional images acquired. - during an initial planning phase (P 1), - - obtaining and memorising a preoperative three-dimensional image comprising a target vascular structure of a patient, - - determining a first three-dimensional anatomical model (M 1) specific to the patient from the three-dimensional image acquired, this first three-dimensional anatomical model (M 1) being located in the same spatial reference as the three-dimensional image, - - obtaining and memorising a preoperative three-dimensional image comprising a target vascular structure of a patient, - - determining a first three-dimensional anatomical model (M 1) specific to the patient from the three-dimensional image acquired, this first three-dimensional anatomical model (M 1) being located in the same spatial reference as the three-dimensional image, - during an intervention phase (P 2), - - acquiring one or several perioperative two-dimensional images comprising the target vascular structure of the patient, opacified or not, - - estimating a rigid transformation between the preoperative three-dimensional image and the perioperative two-dimensional images, said system being characterised in that it is further adapted for: - - estimating an elastic transformation between said three-dimensional image and the two-dimensional images according to the rigid transformation and a simulation of vascular deformations induced by introducing the tool into the target vascular structure, said simulation being obtained as a function of a local state of the target vascular structure, a relationship between the target vascular structure and its direct environment, and mechanical properties of the endovascular tool, - - applying a combination of the rigid transformation and of the elastic transformation to the first three-dimensional anatomical model (M 1) specific to the patient in order to obtain a second three-dimensional model (M 2) specific to the patient, - - displaying on the viewing unit said second three-dimensional model specific to the patient in superposition on the two-dimensional images acquired. - - acquiring one or several perioperative two-dimensional images comprising the target vascular structure of the patient, opacified or not, - - estimating a rigid transformation between the preoperative three-dimensional image and the perioperative two-dimensional images, said system being characterised in that it is further adapted for: - - estimating an elastic transformation between said three-dimensional image and the two-dimensional images according to the rigid transformation and a simulation of vascular deformations induced by introducing the tool into the target vascular structure, said simulation being obtained as a function of a local state of the target vascular structure, a relationship between the target vascular structure and its direct environment, and mechanical properties of the endovascular tool, - - applying a combination of the rigid transformation and of the elastic transformation to the first three-dimensional anatomical model (M 1) specific to the patient in order to obtain a second three-dimensional model (M 2) specific to the patient, - - displaying on the viewing unit said second three-dimensional model specific to the patient in superposition on the two-dimensional images acquired.