title: kV cone-beam CT-based IGRT: a clinical review.
abstract: OBJECTIVE
  Delivery of high radiation doses while simultaneously sparing organs at risk requires advanced imaging for target volume definition, highly conformal dose distributions of intensity modulated radiotherapy (IMRT), and narrow planning target volume (PTV) margins. Three-dimensional image-guided radiotherapy (IGRT) with cone-beam computer tomography (CBCT), which results in more precise target localization, is quickly replacing two-dimensional (2D) IGRT. An overview on the clinical applications of kilovoltage gantry-mounted CBCT systems with emphasis on the most frequently targeted body sites (prostate, lung, head and neck) is provided based on a review of the relevant literature. Alternative imaging methods and their advantages/disadvantages are discussed.
  
  
  RESULTS
  IGRT with soft tissue detection improves set-up accuracy and is currently replacing 2D verification and frame-based stereotactic treatments; safety margins are significantly reduced by this IGRT technology. In addition, systematic changes of tumor volume and shape and of the normal tissue can be monitored allowing for adaptation of radiotherapy. IGRT in combination with conformal treatment planning allows for hypofractionated dose escalation, which results in improved rates of local tumor control with low rates of toxicity.
  
  
  CONCLUSIONS
  CBCT allows for daily pretreatment position verification and online correction of set-up errors which improves the precision of patient repositioning with the possibility of shrinking safety margins, sparing organs at risk, and escalating radiation doses. A trend for better clinical outcome can be observed.
authors.affiliation: Department of Radiation Oncology, University Medical Center Mannheim, University of Heidelberg, Mannheim, Germany. judit.boda-heggemann@umm.de
authors.forename: Judit
authors.initials: J
authors.lastname: Boda-Heggemann
authors.forename: Frank
authors.initials: F
authors.lastname: Lohr
authors.forename: Frederik
authors.initials: F
authors.lastname: Wenz
authors.forename: Michael
authors.initials: M
authors.lastname: Flentje
authors.forename: Matthias
authors.initials: M
authors.lastname: Guckenberger
mesh_terms: D054893:Cone-Beam Computed Tomography / Q000379:methods*; D006258:Head and Neck Neoplasms / Q000532:radiotherapy; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000592:standards; D008175:Lung Neoplasms / Q000532:radiotherapy; D011881:Radiotherapy, Computer-Assisted / Q000379:methods* / Q000592:standards*