title: A new split arc VMAT technique for lymph node positive breast cancer.
abstract: OBJECTIVE
  To investigate different volumetric modulated arc therapy (VMAT) field designs for lymph node positive breast cancer patients when compared to conventional static fields and standard VMAT designs.
  
  
  METHODS
  Nineteen breast cancer patients with lymph node involvement (eleven left and eight right sided) were retrospectively analyzed with different arc designs. Proposed split arc designs with total rotations of 2×190° and 2×240° were compared to conventional field in field (FinF) and previously published non-split arc techniques with the same amount of total rotations.
  
  
  RESULTS
  All VMAT plans were superior in dose conformity, when compared to the FinF plans. Split arc design decreased significantly ipsilateral lung dose and heart V5Gy for both left and right sided cases, when compared to non-split VMAT designs. For left sided cases no significant differences were seen in contralateral lung mean dose or V5Gy between different VMAT designs. For right sided cases the contralateral lung dose V5Gy was significantly higher in split VMAT group, when compared to non-split VMAT designs. The contralateral breast dose V5Gy increased significantly for split VMAT plans for both sides, when compared to non-split VMAT designs or FinF plans.
  
  
  CONCLUSIONS
  The proposed split VMAT technique was shown to be superior to previously published non-split VMAT and conventional FinF techniques significantly reducing dose to the ipsilateral lung and heart. However, this came with the expense of an increase in the dose to the contralateral breast and for right-sided cases to the contralateral lung.
authors.affiliation: Department of Oncology, Tampere University Hospital, PO BOX 2000, FI-33521 Tampere, Finland; Department of Medical Physics, Tampere University Hospital, PO BOX 2000, FI-33521 Tampere, Finland; Department of Radiation Oncology, Wellington Blood and Cancer Centre, Wellington Hospital, Wellington 6242, New Zealand. Electronic address: eeva.boman@ccdhb.org.nz.
authors.forename: Eeva
authors.initials: E
authors.lastname: Boman
authors.affiliation: Department of Oncology, Tampere University Hospital, PO BOX 2000, FI-33521 Tampere, Finland; Department of Medical Physics, Tampere University Hospital, PO BOX 2000, FI-33521 Tampere, Finland. Electronic address: Maija.Rossi@pshp.fi.
authors.forename: Maija
authors.initials: M
authors.lastname: Rossi
authors.affiliation: Department of Oncology, Tampere University Hospital, PO BOX 2000, FI-33521 Tampere, Finland. Electronic address: Mikko.Haltamo@pshp.fi.
authors.forename: Mikko
authors.initials: M
authors.lastname: Haltamo
authors.affiliation: Department of Oncology, Tampere University Hospital, PO BOX 2000, FI-33521 Tampere, Finland. Electronic address: Tanja.Skytta@pshp.fi.
authors.forename: Tanja
authors.initials: T
authors.lastname: Skyttä
authors.affiliation: Department of Oncology, Tampere University Hospital, PO BOX 2000, FI-33521 Tampere, Finland; Department of Medical Physics, Tampere University Hospital, PO BOX 2000, FI-33521 Tampere, Finland. Electronic address: Mika.Kapanen@pshp.fi.
authors.forename: Mika
authors.initials: M
authors.lastname: Kapanen
keywords: Breast radiotherapy; Treatment planning; VMAT