gms | German Medical Science

48th Meeting of the Particle Therapy Co-Operative Group

Particle Therapy Co-Operative Group (PTCOG)

28.09. - 03.10.2009, Heidelberg

Advanced Measurements of Depth Dose Distributions for Mono-energetic Carbon Ion Beams

Meeting Abstract

  • M. Sakama - Heavy Ion Medical Research Center, Gunma University, Showa, Maebashi, Gunma, Japan
  • T. Kanai - Heavy Ion Medical Research Center, Gunma University, Showa, Maebashi, Gunma, Japan
  • K. Yusa - Heavy Ion Medical Research Center, Gunma University, Showa, Maebashi, Gunma, Japan
  • M. Tashiro - Heavy Ion Medical Research Center, Gunma University, Showa, Maebashi, Gunma, Japan
  • K. Torikai - Heavy Ion Medical Research Center, Gunma University, Showa, Maebashi, Gunma, Japan
  • H. Shimada - Heavy Ion Medical Research Center, Gunma University, Showa, Maebashi, Gunma, Japan
  • S. Yamada - Heavy Ion Medical Research Center, Gunma University, Showa, Maebashi, Gunma, Japan
  • T. Inaniwa - Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Showa, Maebashi, Gunma, Japan
  • A. Fukumura - Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Showa, Maebashi, Gunma, Japan

PTCOG 48. Meeting of the Particle Therapy Co-Operative Group. Heidelberg, 28.09.-03.10.2009. Düsseldorf: German Medical Science GMS Publishing House; 2009. Doc09ptcog171

DOI: 10.3205/09ptcog171, URN: urn:nbn:de:0183-09ptcog1718

Published: September 24, 2009

© 2009 Sakama et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by-nc-nd/3.0/deed.en). You are free: to Share – to copy, distribute and transmit the work, provided the original author and source are credited.


Outline

Text

In radiotherapy, most common dosimetry is ionization chamber methods and this method needs the beam quality correction factor to obtain the absorbed dose to water for user's beam quality. These factors are constructed from the stopping power ratios, the w values and the perturbation factors for the ionization chamber. The factors for the heavy charged particles have large uncertainties and are constant values for all conditions in the current status. In the Bragg peak region, there are the changes of stopping power ratios, w value, the perturbation factors and the influence of the fragment particles. These influence need to be estimated in order to reduce the uncertainties of the dosimetry in this region, especially for the scanning irradiation, layer stacking irradiation, biological or physical experiments.

The depth dose distributions and fluence distributions of the fragment particles in water are obtained using the Monte Carlo simulations. From these results, the influence of the fragment particles to the stopping power ratio and w values are estimated. The influence of perturbation factors, recombination effect and polarity effect in the high LET region need to be estimated. In mono-energetic carbon ion beams of 290 and 400 MeV/n, the depth dose distributions in water were measured in detail using three plane-parallel ionization chambers (PTW3, Advanced Markus, PTW34423, Markus, PTW34001, Roos). The recombination effects in the Bragg peak region were 0.3% to 2% depending on the energy and the ionization chamber types due to mainly the initial recombination and the polarity effects were within 0.2%. In the Bragg peak region, absorbed dose obtained by the Markus chamber was about 2% lower than those by other PPIC due to the perturbation factors and recombination effect. It will be possible that the beam quality correction factors in the Bragg peak regions are approximately 3% larger than those in the plateau regions.