title: A comparison of three different VMAT techniques for the delivery of lung stereotactic ablative radiation therapy.
abstract: The purpose of this study was to investigate coplanar and non-coplanar volumetric modulated arc therapy (VMAT) delivery techniques for stereotactic ablative radiation therapy (SABR) to the lung.
  
  
  
  For ten patients who had already completed a course of radiation therapy for early stage lung cancer, three new SABR treatment plans were created using (1) a coplanar full arc (FA) technique, (2) a coplanar partial arc technique (PA) and (3) a non-coplanar technique utilising three partial arcs (NCA). These plans were evaluated using planning target volume (PTV) coverage, dose to organs at risk, and high and intermediate dose constraints as incorporated by radiation therapy oncology group (RTOG) 1021.
  
  
  
  When the FA and PA techniques were compared to the NCA technique, on average the PTV coverage (V 54Gy) was similar (P = 0.15); FA (95.1%), PA (95.11%) and NCA (95.71%). The NCA resulted in a better conformity index (CI) of the prescription dose (0.89) when compared to the FA technique (0.88, P = 0.23) and the PA technique (0.83, P = 0.06). The NCA technique improved the intermediate dose constraints with a statistically significant difference for the D 2cm and R 50% when compared with the FA (P < 0.03 and <0.0001) and PA (P < 0.04 and <0.0001) techniques. The NCA technique reduced the maximum spinal cord dose by 2.72 and 4.2 Gy when compared to the PA and FA techniques respectively. Mean lung doses were 4.09, 4.31 and 3.98 Gy for the FA, PA and NCA techniques respectively.
  
  
  
  The NCA VMAT technique provided the highest compliance to RTOG 1021 when compared to coplanar techniques for lung SABR. However, single FA coplanar VMAT was suitable for 70% of patients when minor deviations to both the intermediate dose and organ at risk (OAR) constraints were accepted.
authors.affiliation: Radiation Oncology Centres Mater Private Hospital Springfield Queensland Australia; Science and Engineering Faculty Queensland University of Technology Brisbane Queensland Australia.
authors.forename: Rhys
authors.initials: R
authors.lastname: Fitzgerald
authors.affiliation: Faculty of Health Queensland University of Technology Brisbane Queensland Australia.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Owen
authors.affiliation: Division of Radiation Therapy Princess Alexandra Hospital Woolloongabba Queensland Australia; Radiation Oncology Mater Centre South Brisbane Queensland Australia.
authors.forename: Catriona
authors.initials: C
authors.lastname: Hargrave
authors.affiliation: Department of Radiation Oncology Princess Alexandra Hospital Woolloongabba Queensland Australia.
authors.forename: David
authors.initials: D
authors.lastname: Pryor
authors.affiliation: Division of Radiation Therapy Princess Alexandra Hospital Woolloongabba Queensland Australia.
authors.forename: Tamara
authors.initials: T
authors.lastname: Barry
authors.affiliation: Department of Radiation Oncology Princess Alexandra Hospital Woolloongabba Queensland Australia.
authors.forename: Margot
authors.initials: M
authors.lastname: Lehman
authors.affiliation: QFAB Bioinformatics Institute for Molecular Bioscience University of Queensland Queensland Australia.
authors.forename: Anne
authors.initials: A
authors.lastname: Bernard
authors.affiliation: Department of Radiation Oncology Princess Alexandra Hospital Woolloongabba Queensland Australia.
authors.forename: Tao
authors.initials: T
authors.lastname: Mai
authors.affiliation: Division of Radiation Physics Princess Alexandra Hospital Woolloongabba Queensland Australia.
authors.forename: Venkatakrishnan
authors.initials: V
authors.lastname: Seshadri
authors.affiliation: Science and Engineering Faculty Queensland University of Technology Brisbane Queensland Australia.
authors.forename: Andrew
authors.initials: A
authors.lastname: Fielding
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000532:radiotherapy*; D008297:Male; D058958:Organs at Risk; D016634:Radiosurgery / Q000009:adverse effects / Q000379:methods*; D011879:Radiotherapy Dosage; D050397:Radiotherapy, Intensity-Modulated / Q000009:adverse effects / Q000379:methods*
keywords: Dosimetry; lung cancer; stereotactic ablative radiation therapy; treatment planning; volumetric modulated arc therapy