title: Differences in the definition of internal target volumes using slow CT alone or in combination with thin-slice CT under breath-holding conditions during the planning of stereotactic radiotherapy for lung cancer.
abstract: OBJECTIVE
  To investigate how the delineations of the internal target volume (ITV) made from 'slow' CT alter with reference to 'thin-slice' CT.
  
  
  METHODS
  Thin-slice CT images taken under breath-holding conditions and slow CT images taken under shallow-breathing conditions (8s/image) of 11 lung cancers were used for this study. Five radiation oncologists delineated ITV of the 11 lesions using slow CT images (ITV1), and then redefined them with reference to thin-slice CT images (ITV2). SD-images (standard deviation image) were created for all patients from ITV images in order to visualize the regional variation of the ITVs.
  
  
  RESULTS
  The mean value of ITV2 was smaller than that initially defined by ITV1. There was no significant change in ITV1 and ITV2 between operators with regard to standard deviation in volume. There was a significant difference in the distribution of the ratio of ITV1 to ITV2 obtained on thin-slice CTs between cases with and without ground glass opacity. In cases without ground glass opacity there was a tendency for ITV2 to have a smaller volume than ITV1.
  
  
  CONCLUSIONS
  Combined use of slow CT and thin-slice CT in delineation of ITV contours appeared to be useful in making adjustments for obscured tumor images caused by respiratory movement.
authors.affiliation: Department of Radiology, Keio University, 35 Shinanomachi, Shinjuku, Tokyo, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Seki
authors.forename: Etsuo
authors.initials: E
authors.lastname: Kunieda
authors.forename: Atsuya
authors.initials: A
authors.lastname: Takeda
authors.forename: Tomoaki
authors.initials: T
authors.lastname: Nagaoka
authors.forename: Hossain M
authors.initials: HM
authors.lastname: Deloar
authors.forename: Takatsugu
authors.initials: T
authors.lastname: Kawase
authors.forename: Junichi
authors.initials: J
authors.lastname: Fukada
authors.forename: Osamu
authors.initials: O
authors.lastname: Kawaguchi
authors.forename: Minoru
authors.initials: M
authors.lastname: Uematsu
authors.forename: Atsushi
authors.initials: A
authors.lastname: Kubo
mesh_terms: D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging / Q000601:surgery*; D009929:Organ Size; D016634:Radiosurgery / Q000379:methods*; D012119:Respiration; D014057:Tomography, X-Ray Computed / Q000379:methods*