title: Trajectory Modulated Arc Therapy: A Fully Dynamic Delivery With Synchronized Couch and Gantry Motion Significantly Improves Dosimetric Indices Correlated With Poor Cosmesis in Accelerated Partial Breast Irradiation.
abstract: OBJECTIVE
  To develop planning and delivery capabilities for linear accelerator-based nonisocentric trajectory modulated arc therapy (TMAT) and to evaluate the benefit of TMAT for accelerated partial breast irradiation (APBI) with the patient in prone position.
  
  
  METHODS
  An optimization algorithm for volumetrically modulated arc therapy (VMAT) was generalized to allow for user-defined nonisocentric TMAT trajectories combining couch rotations and translations. After optimization, XML scripts were automatically generated to program and subsequently deliver the TMAT plans. For 10 breast patients in the prone position, TMAT and 6-field noncoplanar intensity modulated radiation therapy (IMRT) plans were generated under equivalent objectives and constraints. These plans were compared with regard to whole breast tissue volume receiving more than 100%, 80%, 50%, and 20% of the prescription dose.
  
  
  RESULTS
  For TMAT APBI, nonisocentric collision-free horizontal arcs with large angular span (251.5 ± 7.9°) were optimized and delivered with delivery time of ∼4.5 minutes. Percentage changes of whole breast tissue volume receiving more than 100%, 80%, 50%, and 20% of the prescription dose for TMAT relative to IMRT were -10.81% ± 6.91%, -27.81% ± 7.39%, -14.82% ± 9.67%, and 39.40% ± 10.53% (P≤.01).
  
  
  CONCLUSIONS
  This is a first demonstration of end-to-end planning and delivery implementation of a fully dynamic APBI TMAT. Compared with IMRT, TMAT resulted in marked reduction of the breast tissue volume irradiated at high doses.
authors.affiliation: Department of Radiation Oncology, Stanford University, California.
authors.forename: Jieming
authors.initials: J
authors.lastname: Liang
authors.affiliation: Department of Radiation Oncology, Stanford University, California.
authors.forename: Todd
authors.initials: T
authors.lastname: Atwood
authors.affiliation: Department of Radiation Oncology, Stanford University, California.
authors.forename: Rie
authors.initials: R
authors.lastname: von Eyben
authors.affiliation: Department of Radiation Oncology, Stanford University, California.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Fahimian
authors.affiliation: Department of Radiation Oncology, Stanford University, California.
authors.forename: Erika
authors.initials: E
authors.lastname: Chin
authors.affiliation: Department of Radiation Oncology, Stanford University, California.
authors.forename: Kathleen
authors.initials: K
authors.lastname: Horst
authors.affiliation: Department of Physics, University of British Columbia, British Columbia.
authors.forename: Karl
authors.initials: K
authors.lastname: Otto
authors.affiliation: Department of Radiation Oncology, Stanford University, California. Electronic address: dimitre.hristov@stanford.edu.
authors.forename: Dimitre
authors.initials: D
authors.lastname: Hristov
mesh_terms: D000465:Algorithms; D001943:Breast Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D015412:Mastectomy, Segmental; D010315:Particle Accelerators / Q000295:instrumentation; D016684:Prone Position; D011859:Radiography; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D061089:Radiotherapy, Image-Guided / Q000295:instrumentation / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000295:instrumentation / Q000379:methods*