title: Golden beam data for proton pencil-beam scanning.
abstract: Proton, as well as other ion, beams applied by electro-magnetic deflection in pencil-beam scanning (PBS) are minimally perturbed and thus can be quantified a priori by their fundamental interactions in a medium. This a priori quantification permits an optimal reduction of characterizing measurements on a particular PBS delivery system. The combination of a priori quantification and measurements will then suffice to fully describe the physical interactions necessary for treatment planning purposes. We consider, for proton beams, these interactions and derive a 'Golden' beam data set. The Golden beam data set quantifies the pristine Bragg peak depth-dose distribution in terms of primary, multiple Coulomb scatter, and secondary, nuclear scatter, components. The set reduces the required measurements on a PBS delivery system to the measurement of energy spread and initial phase space as a function of energy. The depth doses are described in absolute units of Gy(RBE) mm² Gp⁻¹, where Gp equals 10⁹ (giga) protons, thus providing a direct mapping from treatment planning parameters to integrated beam current. We used these Golden beam data on our PBS delivery systems and demonstrated that they yield absolute dosimetry well within clinical tolerance.
authors.affiliation: Department of Radiation Oncology, Massachusetts General Hospital & Harvard Medical School, Boston, MA, USA. bclasie@partners.org
authors.forename: Benjamin
authors.initials: B
authors.lastname: Clasie
authors.forename: Nicolas
authors.initials: N
authors.lastname: Depauw
authors.forename: Maurice
authors.initials: M
authors.lastname: Fransen
authors.forename: Carles
authors.initials: C
authors.lastname: Gomà
authors.forename: Hamid Reza
authors.initials: HR
authors.lastname: Panahandeh
authors.forename: Joao
authors.initials: J
authors.lastname: Seco
authors.forename: Jacob B
authors.initials: JB
authors.lastname: Flanz
authors.forename: Hanne M
authors.initials: HM
authors.lastname: Kooy
mesh_terms: D000465:Algorithms; D002138:Calibration; D006801:Humans; D007477:Ions; D015233:Models, Statistical; D009010:Monte Carlo Method; D016011:Normal Distribution; D011522:Protons; D011839:Radiation, Ionizing; D011874:Radiometry / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results
chemical_list: D007477:Ions; D011522:Protons