Individualized selection of beam angles and treatment isocenter in tangential breast IMRT

Publication date: Available online 14 February 2017
Source:International Journal of Radiation Oncology*Biology*Physics
Author(s): Joan Penninkhof, Sara Spadola, Sebastiaan Breedveld, Margreet Baaijens, Nico Lanconelli, Ben Heijmen
Purpose/objectivePropose a novel method for individualized selection of beam angles and treatment isocenter in tangential breast IMRT.Methods and MaterialsFor each patient, beam and isocenter selection starts with the fully automatic generation of a large database of IMRT plans (up to 847 in this study), each of these plans belongs to a unique combination of isocenter position, lateral beam angle, and medial beam angle. The imposed hard planning constraint on patient maximum dose may result in plans with unacceptable target dose delivery. Such plans are excluded from further analyses. Due to differences in beam set-up, database plans differ in mean doses in organs-at-risk (OARs). These mean doses are used to construct 2-dimensional graphs, showing relationships between 1) contralateral breast dose and ipsilateral lung dose, and 2) contralateral breast dose and heart dose (analyzed only for left-sided). The graphs can be used for selection of the isocenter and beam angles with the optimal, patient-specific trade-offs between the mean OAR doses. For 30 previously treated patients (15 left-sided and 15 right-sided tumors), graphs were generated considering only the clinically applied isocenter with 121 tangential beam angle pairs. For 20 of the 30 patients, 6 alternative isocenters were investigated as well.ResultsComputation time for automatic generation of 121 IMRT plans took on average 30 minutes. The generated graphs demonstrated large variations in trade-offs between conflicting OAR objectives, depending on beam angles and patient anatomy. For patients with isocenter optimization, 847 IMRT plans were considered. Adding isocenter position optimization next to beam angle optimization had a small impact on the final plan quality.ConclusionA method is proposed for individualized selection of beam angles in tangential breast IMRT. This may be especially important for patients with cardiac risk factors or an enhanced risk for development of contralateral breast cancer.

Teaser

A method for individualized selection of beam angles and treatment isocenter in tangential breast IMRT, based on graphical representations of mean OAR doses in a large database of automatically generated IMRT plans, is presented. The method may be especially useful for patients with cardiac risk factors or an enhanced risk for induction of a tumor in the contralateral breast.


http://ift.tt/2ktFJRL