A precise delination of the target is a critical part of radiosurgical treatment planning of brain AVMs. This target delineation is performed by drawing the contours of the nidus, the active part of the AVM, on calibrated (using a stereotactic frame) digital subtraction angiography (DSA) projections assuming that DSA remains the imaging gold standard. This manual delineation is a difficult and time consuming task. Inconsistency between the delineations performed in the different views, usually AP and lateral, may led to a wrong target and so on to a poor anatomical result. The aims of this study are 1) to describe an original and helpful user interface to delineate a 3D target by drawing its contours on multiple 2D projections from DSA; 2) to validate the interest of this interface.