title: Use of BANG polymer gel for dose measurements in a 68 MeV proton beam.
abstract: BANG polymer gel dosimetry using magnetic resonance imaging (MRI) was applied to an ophthalmologic 68 MeV proton beam. The object was to examine the use of BANG gel for the verification of proton fields in eye tumor therapy and to explore the applicability of polymer gel dosimetry in proton therapy under practical aspects. The gel phantoms were irradiated with monoenergetic and modulated proton beams. MRI analysis was carried out at clinical 1.5 and 3 T MR scanners. At constant LET, results show a linear relationship between spin-spin relaxation rates and dose. However, depth dose curves in BANG gel reveal a quenching of the Bragg maximum due to LET effects. The dose response of the gel for monoenergetic protons and spread-out depth dose distributions can be calculated based on ionization chamber measurements. Experiment and calculations show good agreement and indicate that BANG polymer gels might become a valuable tool in proton therapy quality assurance.
authors.affiliation: Hahn-Meitner Institut, Augentumortherapie, Glienicker Strasse 100, D-14109 Berlin, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Heufelder
authors.forename: S
authors.initials: S
authors.lastname: Stiefel
authors.forename: M
authors.initials: M
authors.lastname: Pfaender
authors.forename: L
authors.initials: L
authors.lastname: Lüdemann
authors.forename: G
authors.initials: G
authors.lastname: Grebe
authors.forename: J
authors.initials: J
authors.lastname: Heese
mesh_terms: D019544:Equipment Failure Analysis; D005782:Gels / Q000528:radiation effects*; D006801:Humans; D018499:Linear Energy Transfer; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods*; D008962:Models, Theoretical; D011108:Polymers / Q000528:radiation effects*; D061766:Proton Therapy; D011874:Radiometry / Q000295:instrumentation* / Q000379:methods; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D011882:Radiotherapy, High-Energy / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: C106521:BANG polymer gel; D005782:Gels; D011108:Polymers