IMRT optimization by constraint conjugations in boolean transition regions of overlapping structures

Purpose/Objective: In IMRT of tumors abutting critical structures, the PTV substantially overlaps with normal tissue volumes (NTV). Standard IMRT optimization techniques impose constraints only on the PTV and NTV and thus fail to modulate predictably the dose gradient in these overlapping regions. The purpose of this paper is to present the Transitional Boolean Dose Constraints Conjugation, or the TBDCC, optimization technique. This IMRT optimization technique uses constraints conjugation to achieve predictable IMRT dose gradients across overlapping tissue volumes. We report on the TBDCC technique and its effectiveness in more than 150 IMRT patients’ plans otherwise difficult to optimize by standard techniques. Patients presented include post-prostatectomy with iliac nodes, cervix with para-aortic nodes, large meningioma abutting optic nerves and chiasm, and mesothelioma invading the heart and lung pleura. Their comparative IMRT plans, with and without constraints conjugation, are presented.