The development of target-eye-view maps for selection of coplanar or noncoplanar beams in conformal radiotherapy treatment planning

Abstract

Three-dimensional conformal radiotherapy allows the use of tightly conformed, multiple coplanar or noncoplanar beams. However, visualizing the spatial relationships between the target volume and adjacent critical structures is not always obvious or intuitive. Tools such as beam's eye view (BEV) have aided in this process and been very useful. In this study, a target-eye-view (TEV) map is developed as a functional extension of BEVs. The TEV map for a critical structure is created by checking the BEVs for all gantries and table rotations. For each possible BEV, the amount of overlap between the planning target volume (PTV) and the organ at risk (OAR) is determined. This information is presented in a Mercator spherical map, where the color tone indicates the amount of overlap between the PTV and the OAR. A composite TEV map is then created by summing the TEV grading scores for all OARs. The composite map shows beam orientations with the most overlap being light and the least overlap being dark, thus simplifying the selection of appropriate beam angles. The accuracy of the TEV maps has been confirmed separately with corresponding BEVs generated by a three-dimensional treatment planning system.