title: Lung tumor reproducibility with active breath control (ABC) in image-guided radiotherapy based on cone-beam computed tomography with two registration methods.
abstract: OBJECTIVE
  To study the inter- and intrafraction tumor reproducibility with active breath control (ABC) utilizing cone-beam computed tomography (CBCT), and compare validity of registration with two different regions of interest (ROI).
  
  
  METHODS
  Thirty-one lung tumors in 19 patients received conventional or stereotactic body radiotherapy with ABC. During each treatment, patients had three CBCT scanned before and after online position correction and after treatment. These CBCT images were aligned to the planning CT using the gray scale registration of tumor and bony registration of the thorax, and tumor position uncertainties were then determined.
  
  
  RESULTS
  The interfraction systematic and random translation errors in the left-right (LR), superior-inferior (SI) and anterior-posterior (AP) directions were 3.6, 4.8, and 2.9mm; 2.5, 4.5, and 3.5mm, respectively, with gray scale alignment; 1.9, 4.3, 2.0mm and 2.5, 4.4, 2.9mm, respectively, with bony alignment. The interfraction systematic and random rotation errors with gray scale and bony alignment groups ranged from 1.4° to 3.0° and 0.8° to 2.3°, respectively. The intrafraction systematic and random errors with gray scale registration in LR, SI, AP directions were 0.9, 2.0, 1.8mm and 1.5, 1.7, 2.9mm, respectively, for translation; 1.5°, 0.9°, 1.0° and 1.2°, 2.2°, 1.8°, respectively, for rotation. The translational errors in SI direction with bony alignment were significantly larger than that of gray scale (p<0.05).
  
  
  CONCLUSIONS
  With CBCT guided online correction the interfraction positioning errors can be markedly reduced. The intrafraction errors were not diminished by the use of ABC. Rotation errors were not very remarkable both inter- and intrafraction. Gray scale alignment of tumor may provide a better registration in SI direction.
authors.affiliation: Department of Radiation Oncology, Sichuan University, Chengdu, People's Republic of China.
authors.forename: Xin
authors.initials: X
authors.lastname: Wang
authors.forename: Renming
authors.initials: R
authors.lastname: Zhong
authors.forename: Sen
authors.initials: S
authors.lastname: Bai
authors.forename: Qingfeng
authors.initials: Q
authors.lastname: Xu
authors.forename: Yaqin
authors.initials: Y
authors.lastname: Zhao
authors.forename: Jin
authors.initials: J
authors.lastname: Wang
authors.forename: Xiaoqin
authors.initials: X
authors.lastname: Jiang
authors.forename: Yali
authors.initials: Y
authors.lastname: Shen
authors.forename: Feng
authors.initials: F
authors.lastname: Xu
authors.forename: Yuquan
authors.initials: Y
authors.lastname: Wei
mesh_terms: D000328:Adult; D000368:Aged; D054893:Cone-Beam Computed Tomography / Q000379:methods*; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D056888:Patient Positioning; D016634:Radiosurgery / Q000379:methods*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D015203:Reproducibility of Results; D012119:Respiration; D012189:Retrospective Studies; D016896:Treatment Outcome