title: Ranges of ions in metals for use in particle treatment planning.
abstract: In proton and ion radiotherapy, the range of particles is calculated from x-ray computed tomography (CT) numbers. Due to the strong absorption of x-rays in a metal and a cut-off for large Hounsfield units (HU) in the software of most CT-scanners, a range calculation in metals cannot be based on the measured HU. This is of special importance when metal implants such as gold fillings or hip prostheses are close to the treatment volume. In order to overcome this problem in treatment planning for heavy charged particles, the correct ranges of ions in the metal relative to water have to be assigned in the CT data. Measurements and calculations of carbon ion ranges in various metals are presented that can be used in treatment planning to allow for a more accurate range calculation of carbon ion beams in titanium, steel, tungsten and gold. The suggested values for the relative water-equivalent range and their uncertainties are 3.13 (+/-3%) for titanium, 5.59 (+/-3%) for stainless steel and 10.25 (+/-4%) for gold.
authors.affiliation: Division for Medical Physics in Radiotherapy (E040), German Cancer Research Center, INF 280, 69120 Heidelberg, Germany. o.jaekel@dkfz.de
authors.forename: Oliver
authors.initials: O
authors.lastname: Jäkel
mesh_terms: D016477:Artifacts; D002250:Carbon Radioisotopes / Q000032:analysis*; D007477:Ions; D008670:Metals / Q000032:analysis*; D011874:Radiometry / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D002250:Carbon Radioisotopes; D007477:Ions; D008670:Metals