title: Digital tomosynthesis for respiratory gated liver treatment: clinical feasibility for daily image guidance.
abstract: OBJECTIVE
  Breath-hold (BH) treatment minimizes internal target volumes (ITV) when treating sites prone to motion. Digital tomosynthesis (DTS) imaging has advantages over cone-beam CT (CBCT) for BH imaging: BH-DTS scan can be completed during a single breath-hold, whereas BH-CBCT is usually acquired by parsing the gantry rotation into multiple BH segments. This study evaluates the localization accuracy of DTS for BH treatment of liver tumors.
  
  
  METHODS
  Both planning CT and on-board DTS/CBCT images were acquired under BH, using the planning CT BH window as reference. Onboard imaging data sets included two independent DTS orientations (coronal and sagittal), and CBCT images. Soft tissue target positioning was measured by each imaging modality and translated into couch shifts. Performance of the two DTS orientations was evaluated by comparing target positioning with the CBCT benchmark, determined by two observers.
  
  
  RESULTS
  Image data sets were collected from thirty-eight treatment fractions (14 patients). Mean differences between the two DTS methods and the CBCT method were <1 mm in all directions (except the lateral direction with sagittal-DTS: 1.2 mm); the standard deviation was in the range of 2.1-3.5 mm for all techniques. The Pearson correlation showed good interobserver agreement for the coronal-DTS (0.72-0.78). The interobserver agreement for the sagittal-DTS was good for the in-plane directions (0.70-0.82), but poor in the out-of-plane direction (lateral, 0.26).
  
  
  CONCLUSIONS
  BH-DTS may be a simpler alternative to BH-CBCT for onboard soft tissue localization of the liver, although the precision of DTS localization appears to be somewhat lower because of the presence of subtle out-of-plane blur.
authors.affiliation: Department of Radiation Oncology, Duke University Medical Center, Durham, NC 27710, USA. Jackie.Wu@duke.edu
authors.forename: Q Jackie
authors.initials: QJ
authors.lastname: Wu
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Meyer
authors.forename: Jessica
authors.initials: J
authors.lastname: Fuller
authors.forename: Devon
authors.initials: D
authors.lastname: Godfrey
authors.forename: Zhiheng
authors.initials: Z
authors.lastname: Wang
authors.forename: Junan
authors.initials: J
authors.lastname: Zhang
authors.forename: Fang-Fang
authors.initials: FF
authors.lastname: Yin
mesh_terms: D054893:Cone-Beam Computed Tomography / Q000379:methods* / Q000592:standards; D005240:Feasibility Studies; D006801:Humans; D008113:Liver Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy; D009068:Movement; D015588:Observer Variation; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods* / Q000592:standards; D012119:Respiration