Apparatus comprising: an endoluminal device that comprises one or more radiopaque portions and that is configured to move through a lumen of a subject; an output device ; and at least one computer processor configured to: receive, from an extraluminal radiographic imaging device , a sequence of radiographic images of a portion of the subject's body in which the lumen is disposed, during movement of the endoluminal device through the lumen identify locations at which the one or more radiopaque portions of the endoluminal device were imaged during the movement of the endoluminal device through the lumen, by analyzing the sequence of radiographic images; define a set of locations at which the one or more radiopaque portions of the endoluminal device were disposed during the movement of the endoluminal device through the lumen by identifying a sub-set of the identified locations such that each member of the sub-set of the identified locations is disposed within a given distance of at least one other member of the sub-set of the identified locations; estimate an endoluminal path of the device through the lumen, based upon the defined set of locations; and generate an output on the output device. an endoluminal device that comprises one or more radiopaque portions and that is configured to move through a lumen of a subject; an output device ; and at least one computer processor configured to: receive, from an extraluminal radiographic imaging device , a sequence of radiographic images of a portion of the subject's body in which the lumen is disposed, during movement of the endoluminal device through the lumen identify locations at which the one or more radiopaque portions of the endoluminal device were imaged during the movement of the endoluminal device through the lumen, by analyzing the sequence of radiographic images; define a set of locations at which the one or more radiopaque portions of the endoluminal device were disposed during the movement of the endoluminal device through the lumen by identifying a sub-set of the identified locations such that each member of the sub-set of the identified locations is disposed within a given distance of at least one other member of the sub-set of the identified locations; estimate an endoluminal path of the device through the lumen, based upon the defined set of locations; and generate an output on the output device. receive, from an extraluminal radiographic imaging device , a sequence of radiographic images of a portion of the subject's body in which the lumen is disposed, during movement of the endoluminal device through the lumen identify locations at which the one or more radiopaque portions of the endoluminal device were imaged during the movement of the endoluminal device through the lumen, by analyzing the sequence of radiographic images; define a set of locations at which the one or more radiopaque portions of the endoluminal device were disposed during the movement of the endoluminal device through the lumen by identifying a sub-set of the identified locations such that each member of the sub-set of the identified locations is disposed within a given distance of at least one other member of the sub-set of the identified locations; estimate an endoluminal path of the device through the lumen, based upon the defined set of locations; and generate an output on the output device. <EOS>