title: Systematic analysis on the achievable accuracy of PT-PET through automated evaluation techniques.
abstract: BACKGROUND
  Particle Therapy Positron Emission Tomography (PT-PET) is currently the only clinically applied method for in vivo verification of ion-beam radiotherapy during or close in time to the treatment. Since a direct deduction of the delivered dose from the measured activity is not feasible, images are compared to a reference distribution. The achievable accuracy of two image analysis approaches was investigated by means of reproducible phantom benchmark tests. This is an objective method that excludes patient related factors of influence.
  
  
  METHODS
  Two types of phantoms were designed to produce well defined deviations in the activity distributions. Pure range differences were simulated using the first phantom type while the other emulated cavity structures. The phantoms were irradiated with (12)C-ions. PT-PET measurements were performed by means of a camera system installed at the beamline. Different measurement time scenarios were investigated, assuming a PET scanner directly at the irradiation site or placed within the treatment room. The images were analyzed by means of the Pearson Correlation Coefficient (PCC) and a range calculation algorithm combined with a dedicated cavity filling detection method.
  
  
  RESULTS
  Range differences could be measured with an error of less than 2 mm. The range comparison algorithm yielded slightly better results than the PCC method. The filling of a cavity structure could be safely detected if its inner diameter was at least 5 mm.
  
  
  CONCLUSIONS
  Both approaches evaluate the PT-PET data in an objective way and deliver promising results for in-beam and in-room PET for clinical realistic dose rates.
authors.affiliation: OncoRay - National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Helmholtz-Zentrum Dresden-Rossendorf, Germany. Electronic address: stephan.helmbrecht@oncoray.de.
authors.forename: Stephan
authors.initials: S
authors.lastname: Helmbrecht
authors.affiliation: Department of Radiation Oncology, Division of Medical Radiation Physics, Comprehensive Cancer Center, Medical University Vienna, Austria; Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Vienna, Austria. Electronic address: peter.kuess@meduniwien.ac.at.
authors.forename: Peter
authors.initials: P
authors.lastname: Kuess
authors.affiliation: Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Vienna, Austria; Center for Medical Physics and Biomedical Engineering, Medical University Vienna, Austria. Electronic address: wolfgang.birkfellner@meduniwien.ac.at.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Birkfellner
authors.affiliation: OncoRay - National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Helmholtz-Zentrum Dresden-Rossendorf, Germany; Institute of Radiation Oncology, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany. Electronic address: Wolfgang.Enghardt@OncoRay.de.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Enghardt
authors.affiliation: OncoRay - National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Helmholtz-Zentrum Dresden-Rossendorf, Germany. Electronic address: kristin.stuetzer@oncoray.de.
authors.forename: Kristin
authors.initials: K
authors.lastname: Stützer
authors.affiliation: Department of Radiation Oncology, Division of Medical Radiation Physics, Comprehensive Cancer Center, Medical University Vienna, Austria; Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Vienna, Austria. Electronic address: dietmar.georg@meduniwien.ac.at.
authors.forename: Dietmar
authors.initials: D
authors.lastname: Georg
authors.affiliation: Institute of Radiation Physics, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany. Electronic address: f.fiedler@hzdr.de.
authors.forename: Fine
authors.initials: F
authors.lastname: Fiedler
mesh_terms: D003198:Computer Simulation; D063193:Heavy Ion Radiotherapy / Q000379:methods*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008954:Models, Biological; D009369:Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D019047:Phantoms, Imaging; D049268:Positron-Emission Tomography / Q000379:methods*; D011874:Radiometry / Q000379:methods; D011879:Radiotherapy Dosage; D061089:Radiotherapy, Image-Guided / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
keywords: In-vivo-Dosimetrie; Ion beam therapy; Ionenstrahltherapie; Particle Therapy-PET; Pearson Correlation Coefficient; Pearsons Korrelationskoeffizient; Teilchentherapie-PET; in-vivo dosimetry