title: A three-field monoisocentric inverse breast treatment planning technique without half-beam blocking.
abstract: The purpose of this study was to introduce a three-field monoisocentric inverse treatment planning method without half-beam blocks for breast cancer radiation treatments. Three-field monoisocentric breast treatment planning with half-beam blocks limits the tangential field length to 20 cm. A dual-isocenter approach accommodates patients with larger breasts, but prolongs treatment time and may introduce dose uncertainty at the matching plane due to daily setup variations. We developed a novel monoisocentric, three-field treatment planning method without half-beam blocking. The new beam-matching method utilizes the full field size with a single isocenter. Furthermore, an open/IMRT hybrid inverse optimization method was employed to improve dose uniformity and coverage. Geometric beam matching was achieved by rotating the couch, collimator, and gantry together. Formulae for three-field geometric matching were derived and implemented in Pinnacle scripts. This monoisocentric technique can be used for patients with larger breast size. The new method has no constraints on the length of tangential fields. Compared with the dual-isocenter method, it can significantly reduce patient setup time anduncertainties.
authors.affiliation: Washington University. tzhang@radonc.wustl.edu.
authors.forename: Tiezhi
authors.initials: T
authors.lastname: Zhang
authors.forename: Joshua T
authors.initials: JT
authors.lastname: Dilworth
authors.forename: Ovidiu
authors.initials: O
authors.lastname: Marina
authors.forename: Peter
authors.initials: P
authors.lastname: Chen
authors.forename: Lisa
authors.initials: L
authors.lastname: Benedetti
authors.forename: Qiang
authors.initials: Q
authors.lastname: Liu
mesh_terms: D001943:Breast Neoplasms / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D010315:Particle Accelerators; D019047:Phantoms, Imaging; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*