1. A method for positioning a patient prior to administration of an electron treatment using a linear accelerator, the method comprising: obtaining a three-dimensional (3D) diagnostic image of a patient situated on a patient support device prior to the electron treatment; segmenting the 3D diagnostic image to define an internal anatomical feature within a patient's breast; annotating the segmented image to identify an external feature on a surface of the patient's skin; displaying the annotated image from a beam's-eye vie of the linear accelerator; iteratively modifying the physical setup of the patient by at least one of rotating a gantry of the linear accelerator and adjusting the patient support device until the internal and external features are aligned; updating the display to show a perspective of the beam's-eye view in response to the modification of the treatment parameter until a direction of an electron beam of the linear accelerator is aligned along the beam's-eye view to the internal feature; and directing a single electron beam of the linear accelerator along the beam's-eye view toward the internal feature.