title: Dosimetry intercomparison of four proton therapy institutions in Germany employing spot scanning.
abstract: OBJECTIVE
  To verify the consistency of dose and range measurement in an interinstitution comparison among proton therapy institutions in Germany which use the pencil-beam scanning technique.
  
  
  METHODS
  Following a peer-to-peer approach absorbed dose and range have been intercompared in several missions at two hosting centers with two or three visiting physics teams of participating institutions using their own dosimetry equipment. A meta-analysis has been performed integrating the results of the individual missions. Dose has been determined with ionization chambers according to the dosimetry protocol IAEA TRS-398. For determination of the depth of the distal 80% dose the teams used either a scanning water phantom, a variable water column or a multi-layer ionization chamber.
  
  
  RESULTS
  The systematic deviation between measured doses of the participating institutions is less than 1%. Ranges differ systematically less than 0.4mm.
  
  
  CONCLUSIONS
  The match of measured dose and range is better than expected from the respective uncertainties. As all physics teams agree on the assessment of absorbed dose and range, an important prerequisite for a start of joint clinical studies is fulfilled.
authors.affiliation: Westdeutsches Protonentherapiezentrum Essen, Hufelandstr. 55, Essen, Germany. Electronic address: christian.baeumer@uk-essen.de.
authors.forename: Christian
authors.initials: C
authors.lastname: Bäumer
authors.affiliation: Heidelberger Ionenstrahl-Therapiezentrum, Im Neuenheimer Feld 450, Heidelberg, Germany; Heidelberg Institute for Radiation Oncology, Im Neuenheimer Feld 400, Heidelberg, Germany.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Ackermann
authors.affiliation: Rinecker Proton Therapy Center, Schäftlarnstr. 133, München, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Hillbrand
authors.affiliation: Rinecker Proton Therapy Center, Schäftlarnstr. 133, München, Germany.
authors.forename: Franz-Joachim
authors.initials: FJ
authors.lastname: Kaiser
authors.affiliation: Westdeutsches Protonentherapiezentrum Essen, Hufelandstr. 55, Essen, Germany.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Koska
authors.affiliation: Heidelberger Ionenstrahl-Therapiezentrum, Im Neuenheimer Feld 450, Heidelberg, Germany; Heidelberg Institute for Radiation Oncology, Im Neuenheimer Feld 400, Heidelberg, Germany.
authors.forename: Harald
authors.initials: H
authors.lastname: Latzel
authors.affiliation: German Cancer Consortium (DKTK), Germany; OncoRay - National Center for Radiation Research in Oncology, Medical Faculty and University Hospital Carl Gustav Carus, Technische Universität Dresden, Fetscherstr. 74, Dresden, Germany; German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, Heidelberg, Germany.
authors.forename: Armin
authors.initials: A
authors.lastname: Lühr
authors.affiliation: Department of Radiation Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Fetscherstr. 74, Dresden, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Menkel
authors.affiliation: Westdeutsches Protonentherapiezentrum Essen, Hufelandstr. 55, Essen, Germany; German Cancer Consortium (DKTK), Germany; Clinic for Particle Therapy, University Hospital Essen, West German Cancer Center (WTZ), Hufelandstr. 55, Essen, Germany.
authors.forename: Beate
authors.initials: B
authors.lastname: Timmermann
mesh_terms: D002138:Calibration; D005858:Germany; D006801:Humans; D019047:Phantoms, Imaging; D061766:Proton Therapy / Q000379:methods*; D011874:Radiometry / Q000379:methods; D011879:Radiotherapy Dosage
keywords: Ionisationskammer; Nadelstrahlverfahren; Proton therapy; Protonentherapie; Referenzdosimetrie; Reichweite; dosimetry; ionization chamber; pencil-beam scanning; range