title: Monte Carlo simulations on the water-to-air stopping power ratio for carbon ion dosimetry.
abstract: Many papers discussed the I value for water given by the ICRU, concluding that a value of about 80 +/- 2 eV instead of 67.2 eV would reproduce measured ion depth-dose curves. A change in the I value for water would have an effect on the stopping power and, hence, on the water-to-air stopping power ratio, which is important in clinical dosimetry of proton and ion beams. For energies ranging from 50 to 330 MeV/u and for one spread out Bragg peak, the authors compare the impact of the I value on the water-to-air stopping power ratio. The authors calculate ratios from different ICRU stopping power tables and ICRU reports. The stopping power ratio is calculated via track-length dose calculation with SHIELD-HIT07. In the calculations, the stopping power ratio is reduced to a value of 1.119 in the plateau region as compared to the cited value of 1.13 in IAEA TRS-398. At low energies the stopping power ratio increases by up to 6% in the last few tenths of a mm toward the Bragg peak. For a spread out Bragg peak of 13.5 mm width at 130 mm depth, the stopping power ratio increases by about 1% toward the distal end.
authors.affiliation: Department of Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Heidelberg 69120, Germany. k.henkner@dkfz.de
authors.forename: Katrin
authors.initials: K
authors.lastname: Henkner
authors.forename: Niels
authors.initials: N
authors.lastname: Bassler
authors.forename: Nikolai
authors.initials: N
authors.lastname: Sobolevsky
authors.forename: Oliver
authors.initials: O
authors.lastname: Jäkel
mesh_terms: D000388:Air; D002244:Carbon / Q000737:chemistry*; D003198:Computer Simulation; D006801:Humans; D007477:Ions; D015233:Models, Statistical; D009010:Monte Carlo Method; D011522:Protons; D011874:Radiometry / Q000295:instrumentation* / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000295:instrumentation / Q000379:methods; D015203:Reproducibility of Results; D012984:Software; D014867:Water / Q000737:chemistry
chemical_list: D007477:Ions; D011522:Protons; D014867:Water; D002244:Carbon