title: [Assessments setup errors and target margin by 6D couch for primary cervical cancer].
abstract: OBJECTIVE
  To explore the inter and intra-fractional setup variations of HexaPOD evo RT 6-degree-of-freedom treatment couch plus kilovoltage (KV) cone-beam computed tomography (CBCT) in patients with primary cervical cancer and calculate the proper margins of CTV for clinical use.
  
  
  METHODS
  From May 2013 to April 2014, 16 consecutive patients with primary cervical cancer were enrolled. Elekta AXESSE™ image guided radiation therapy (IGRT) modalities and vacuum pad were employed. All patents were treated in a prone position after Lac light correction. Then daily CBCT scans prior to were performed treatment delivery, another CBCT scan after 6D couch online correction and a third one after each treatment. After automatic registration to planning CT, three translational X, Y, Z and three rotational Rx, Ry, Rz shifts were analyzed for intra and inter-fraction assessments and CTV margins.
  
  
  RESULTS
  CBCT plus 6D couch could reduce the inter-fraction errors of X (t = 3.87, P = 0.000), Z (t = -7.92, P = 0.000), Rx (t = 3.05, P = 0.003), Ry (t = -6.87, P = 0.000) statistically and Ry was significantly different between pre and post-treatment (t = 3.242, P = 0.002). As to intra-fraction variations, the CTV margins were 2.74 mm, 3.9 mm and 2.87 mm on X, Y and Z directions respectively.
  
  
  CONCLUSIONS
  Corrections with CBCT and HexaPOD evo RT 6D may considerably reduce the translational and rotational setup variations and gain lower PTV volume for intact cervical cancer. Thus it protects normal tissues better and improves the accuracy of high-precision treatments.
authors.affiliation: Cancer Center, Department of Radiation Oncology, Peking University Third Hospital, Beijing 100191, China.
authors.forename: Qianqian
authors.initials: Q
authors.lastname: Cao
authors.affiliation: Cancer Center, Department of Radiation Oncology, Peking University Third Hospital, Beijing 100191, China; Email: zhulihong510@163.com.
authors.forename: Lihong
authors.initials: L
authors.lastname: Zhu
authors.affiliation: Cancer Center, Department of Radiation Oncology, Peking University Third Hospital, Beijing 100191, China.
authors.forename: Junjie
authors.initials: J
authors.lastname: Wang
authors.affiliation: Cancer Center, Department of Radiation Oncology, Peking University Third Hospital, Beijing 100191, China.
authors.forename: Ang
authors.initials: A
authors.lastname: Qu
authors.affiliation: Cancer Center, Department of Radiation Oncology, Peking University Third Hospital, Beijing 100191, China.
authors.forename: Lihong
authors.initials: L
authors.lastname: Yao
authors.affiliation: Cancer Center, Department of Radiation Oncology, Peking University Third Hospital, Beijing 100191, China.
authors.forename: Shun
authors.initials: S
authors.lastname: Zhou
authors.affiliation: Cancer Center, Department of Radiation Oncology, Peking University Third Hospital, Beijing 100191, China.
authors.forename: Shukun
authors.initials: S
authors.lastname: Jiang
authors.affiliation: Cancer Center, Department of Radiation Oncology, Peking University Third Hospital, Beijing 100191, China.
authors.forename: Haitao
authors.initials: H
authors.lastname: Sun
authors.affiliation: Cancer Center, Department of Radiation Oncology, Peking University Third Hospital, Beijing 100191, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Lin
authors.affiliation: Cancer Center, Department of Radiation Oncology, Peking University Third Hospital, Beijing 100191, China.
authors.forename: Tiandi
authors.initials: T
authors.lastname: Zhao
authors.affiliation: Cancer Center, Department of Radiation Oncology, Peking University Third Hospital, Beijing 100191, China.
authors.forename: Xu
authors.initials: X
authors.lastname: Li
authors.affiliation: Cancer Center, Department of Radiation Oncology, Peking University Third Hospital, Beijing 100191, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Wang
authors.affiliation: Cancer Center, Department of Radiation Oncology, Peking University Third Hospital, Beijing 100191, China.
authors.forename: Anyan
authors.initials: A
authors.lastname: Liao
mesh_terms: D054893:Cone-Beam Computed Tomography; D005260:Female; D006801:Humans; D016684:Prone Position; D011880:Radiotherapy Planning, Computer-Assisted; D061089:Radiotherapy, Image-Guided; D002583:Uterine Cervical Neoplasms