A new concept of stereotactic room with multimodal imaging

The methodology developed by Talairach is based on the use of a specific stereotactic frame and X-ray angiography. Its application to Stereo-Electro-Encephalography (SEEG) requires a distance between the X-ray tube and the imaging plane (cut-film) of about 5 meters, in order to consider the acquisition geometry as a parallel projection. X-ray angiographies are acquired with 2 strainer-like grids attached to the frame. A trajectory avoiding vessels is then determined by simply choosing a grid-hole in the images. The adaptation of this methodology to a digital vascular gantry encounters several problems: • geometric distortion of angiographies due to the image intensifier, • short distance between source and imaging plane (about 1m) that implies a conic projection. This has an immediate effect on the following 4 bullets, ⇒ MR acquisition with stereotactic frame for registering with X-ray angiography, ⇒ fusion of images and computation of trajectories on the workstation, ⇒ adaptation of instrumentation (strainer-like grid) to conic projection, ⇒ positioning of gantry with respect to the stereotactic frame.