title: Robustness quantification methods comparison in volumetric modulated arc therapy to treat head and neck cancer.
abstract: BACKGROUND
  To compare plan robustness of volumetric modulated arc therapy (VMAT) with intensity modulated radiation therapy (IMRT) and to compare the effectiveness of 3 plan robustness quantification methods.
  
  
  METHODS
  The VMAT and IMRT plans were created for 9 head and neck cancer patients. For each plan, 6 new perturbed dose distributions were computed using ±3 mm setup deviations along each of the 3 orientations. Worst-case analysis (WCA), dose-volume histogram (DVH) band (DVHB), and root-mean-square dose-volume histogram (RVH) were used to quantify plan robustness. In WCA, a shaded area in the DVH plot bounded by the DVHs from the lowest and highest dose per voxel was displayed. In DVHB, we displayed the envelope of all DVHs in band graphs of all the 7 dose distributions. The RVH represents the relative volume on the vertical axis and the root-mean-square-dose on the horizontal axis. The width from the first 2 methods at different target DVH indices (such as D95%and D5%) and the area under the RVH curve for the target were used to indicate plan robustness. Results were compared using Wilcoxon signed-rank test.
  
  
  RESULTS
  The DVHB showed that the width at D95%of IMRT was larger than that of VMAT (unit Gy) (1.59 vs 1.18) and the width at D5%of IMRT was comparable to that of VMAT (0.59 vs 0.54). The WCA showed similar results between IMRT and VMAT plans (D95%: 3.28 vs 3.00; D5%: 1.68 vs 1.95). The RVH showed the area under the RVH curve of IMRT was comparable to that of VMAT (1.13 vs 1.15). No statistical significance was found in plan robustness between IMRT and VMAT.
  
  
  CONCLUSIONS
  The VMAT is comparable to IMRT in terms of plan robustness. For the 3 quantification methods, WCA and DVHB are DVH parameter-dependent, whereas RVH captures the overall effect of uncertainties.
authors.affiliation: Department of Radiation Oncology, Mayo Clinic Hospital, Phoenix, Arizona. Electronic address: Liu.Wei@mayo.edu.
authors.forename: Wei
authors.initials: W
authors.lastname: Liu
authors.affiliation: Department of Radiation Oncology, Mayo Clinic Hospital, Phoenix, Arizona.
authors.forename: Samir H
authors.initials: SH
authors.lastname: Patel
authors.affiliation: Department of Radiation Oncology, Mayo Clinic Hospital, Phoenix, Arizona.
authors.forename: Jiajian Jason
authors.initials: JJ
authors.lastname: Shen
authors.affiliation: Department of Radiation Oncology, Mayo Clinic Hospital, Phoenix, Arizona.
authors.forename: Yanle
authors.initials: Y
authors.lastname: Hu
authors.affiliation: Department of Radiation Oncology, Mayo Clinic Hospital, Phoenix, Arizona.
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Harrington
authors.affiliation: Department of Radiation Oncology, Mayo Clinic Hospital, Phoenix, Arizona.
authors.forename: Xiaoning
authors.initials: X
authors.lastname: Ding
authors.affiliation: Department of Radiation Oncology, Mayo Clinic Hospital, Phoenix, Arizona.
authors.forename: Michele Y
authors.initials: MY
authors.lastname: Halyard
authors.affiliation: Department of Radiation Oncology, Mayo Clinic Hospital, Phoenix, Arizona.
authors.forename: Steven E
authors.initials: SE
authors.lastname: Schild
authors.affiliation: Department of Radiation Oncology, Mayo Clinic Hospital, Phoenix, Arizona.
authors.forename: William W
authors.initials: WW
authors.lastname: Wong
authors.affiliation: Department of Radiation Oncology, Mayo Clinic Hospital, Phoenix, Arizona.
authors.forename: Gary A
authors.initials: GA
authors.lastname: Ezzell
authors.affiliation: Department of Radiation Oncology, Mayo Clinic Hospital, Phoenix, Arizona.
authors.forename: Martin
authors.initials: M
authors.lastname: Bues
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006258:Head and Neck Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D050397:Radiotherapy, Intensity-Modulated; D047368:Tumor Burden