A structure map as a visualization aid in three-dimensional treatment planning.

Abstract

Conventional 2-dimensional (2D) radiotherapy planning is performed with sets of beams oriented with respect to axial computed tomography (CT) slices containing relevant anatomical information. In general, the central axis of each beam will be constrained to lie in the plane of a particular CT slice. Further constraining the set of beams to coplanar geometry coincident with a single CT slice (the central slice) allows simultaneous visualization of all possible beam orientations with respect to both the target volume and critical structures as represented on the central CT slice. This is possible due to the existence of noncoplanar viewing orientations. In general, a viewing orientation orthogonal to the plane of the CT slices is chosen. Three-dimensional (3D) modeling removes the beam orientation constraints associated with 2D planning, thus allowing greater flexibility in treatment design. It is, in general, no longer possible to identify a single physical plane upon which one may simultaneously view all possible beam orientations. Construction of a virtual orthogonal hyperplane provides a flat surface upon which critical structures may be mapped with respect to all possible beam orientations, thus creating a medium for simultaneous viewing as an aid to 3D treatment plan design.