title: Experimental verification of a real-time compensation functionality for dose changes due to target motion in scanned particle therapy.
abstract: OBJECTIVE
  Implementation and experimental assessment of a real-time dose compensation system for beam tracking in scanned carbon beam therapy of intrafractionally moving targets.
  
  
  METHODS
  A real-time dose compensation functionality has been developed and implemented at the experimental branch of the beam tracking system at GSI Helmholtzzentrum für Schwerionenforschung (GSI). Treatment plans for different target geometries have been optimized. They have been delivered using scanned carbon ions with beam tracking (BT) and real-time dose compensation combined with beam tracking (RDBT), respectively. Target motion was introduced by a rotating table. Dose distributions were assessed by ionization chamber measurements and dose reconstructions. These distributions have been compared to stationary delivery for BT as well as RDBT. Additionally simulations have been performed to investigate the dependence of delivered dose distributions on varying motion starting phases for BT and RDBT, respectively.
  
  
  RESULTS
  Average measured dose differences between static delivery and motion influenced delivery could be reduced from 27-68 mGy when BT was used to 12-37 mGy when RDBT was used. Nominal dose was 1000 mGy. Simulated dose deliveries showed improvements in dose delivery and robustness against varying starting motion phases when RDBT was used.
  
  
  CONCLUSIONS
  A real-time dose compensation functionality extending the existing beam tracking functionality has been implemented and verified by measurements. Measurements and simulated dose deliveries show that real-time dose compensation can substantially improve delivered dose distributions for large rotational target motion compared to beam tracking alone.
authors: GSI Helmholtzzentrum für Schwerionenforschung GmbH, Planckstraße 1, 64291 Darmstadt, Germany. c.bert@gsi.de
authors: Robert
authors: R
authors: Luchtenborg
authors: Nami
authors: N
authors: Saito
authors: Marco
authors: M
authors: Durante
authors: Christoph
authors: C
authors: Bert
mesh_terms: D000465:Algorithms; D002244:Carbon / Q000627:therapeutic use*; D003198:Computer Simulation; D004867:Equipment Design; D006801:Humans; D007477:Ions; D015233:Models, Statistical; D009038:Motion; D010315:Particle Accelerators; D011874:Radiometry / Q000379:methods; D011878:Radiotherapy / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D011882:Radiotherapy, High-Energy / Q000379:methods; D015203:Reproducibility of Results; D012984:Software
chemical_list: D007477:Ions; D002244:Carbon