Fig. 1From: Characteristics of non-coplanar IMRT in the presence of target-embedded organs at riskTypes of PTV-OAR topologies. Three types of PTV-OAR topologies: type I: PTV (partially) enclosing an OAR; type II OARs loosely distributed around a PTV; type III: one OAR or several OARs encompassing a PTV; contrary to type I, for type II and III the PTV shape needs not to be concaveBack to article page