title: A 4D-optimization concept for scanned ion beam therapy.
abstract: OBJECTIVE
  Scanned carbon beam therapy offers advantageous dose distributions and an increased biological effect. Treating moving targets is complex due to sensitivity to range changes and interplay. We propose a 4D treatment planning concept that considers motion during particle number optimization.
  
  
  METHODS
  The target was subdivided into sectors, one for each motion phase of a 4D-CT. Each sector was non-rigidly transformed to its motion phase and there targeted by a dedicated raster field (RST). Therefore, the resulting 4D-RST compensated target motion and range changes. A 4D treatment control system (TCS) was needed for synchronized delivery to the measured patient motion. 4D-optimized plans were simulated for 9 NSCLC lung cancer patients and compared to static irradiation at end-exhale. A prototype TCS was implemented and successfully tested in a film experiment.
  
  
  RESULTS
  The 4D-optimized treatment plan resulted in only slightly lower dose coverage of the target compared to static optimization, with V 95% of 97.9% (median, range 96.5-99.4%) vs. 99.3% (98.5-99.8%), with negligible overdose. The conformity number was comparable at 88.2% (85.1-92.5%) vs. 85.2% (79.9-91.2%) for 4D and static, respectively.
  
  
  CONCLUSIONS
  We implemented and tested a 4D treatment plan optimization method resulting in highly conformal dose delivery.
authors.affiliation: GSI Helmholtzzentrum für Schwerionenforschung GmbH, Darmstadt, Germany. Electronic address: c.graeff@gsi.de.
authors.forename: Christian
authors.initials: C
authors.lastname: Graeff
authors.forename: Robert
authors.initials: R
authors.lastname: Lüchtenborg
authors.forename: John Gordon
authors.initials: JG
authors.lastname: Eley
authors.forename: Marco
authors.initials: M
authors.lastname: Durante
authors.forename: Christoph
authors.initials: C
authors.lastname: Bert
mesh_terms: D002289:Carcinoma, Non-Small-Cell Lung / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D056973:Four-Dimensional Computed Tomography / Q000379:methods*; D063193:Heavy Ion Radiotherapy / Q000379:methods; D006801:Humans; D007477:Ions; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D009038:Motion; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D020266:Radiotherapy, Conformal / Q000379:methods
chemical_list: D007477:Ions
keywords: 4D-CT; 4D-optimization; Charged particle therapy; Ion beam therapy; Moving targets