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

Improvements in the Fragmentation Model of SHIELD-HIT08

Meeting Abstract

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  • K. Henkner - German Cancer Research Center, Heidelberg, Germany
  • N. Sobolevsky - Institute for Nuclear Research RAS, Moscow, Russian Federation
  • O. Jäkel - Heidelberg Ion Therapy Center, Heidelberg, Germany

PTCOG 48. Meeting of the Particle Therapy Co-Operative Group. Heidelberg, 28.09.-03.10.2009. Düsseldorf: German Medical Science GMS Publishing House; 2009. Doc09ptcog085

DOI: 10.3205/09ptcog085, URN: urn:nbn:de:0183-09ptcog0859

Published: September 24, 2009

© 2009 Henkner et al.
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Outline

Text

Background: The Monte Carlo code SHIELD-HIT (http://www.inr.ru/shield/index.html) is a special version of SHIELD, which was developed in the 1970's. The Heavy Ion Therapy (HIT) version was established in 2001 and further improved to simulate energy loss distributions for heavy ion radiotherapy. In the recent version SHIELD-HIT08 from 2008, Molière multiple Coulomb scattering and a model of the Multi Layer Faraday Cup are implemented.

Material and methods: Simulated angular and depth distributions of primary and secondary particles are compared to measurements from Haettner et al. [1] for a 400 MeV/u carbon ion beam at GSI (Helmholzzentrum für Schwerionenforschung, Darmstadt). The measured distributions of Carbon, Hydrogen, Helium, Lithium, Beryllium and Boron fragments are compared to simulations with SHIELD-HIT.

Within the beam modelling in the MC there are several free parameters which can be varied to adjust the MC results to experimental data. Three of these parameters, influencing the nuclear interactions [2], are studied in a comparison to measured angular and depth distributions. The free parameters are named PARLEV(xx) in SHIELD-HIT.

PARLEV(39) re-normalizes the cross-section of inelastic interactions of ions. A decrease of the value decreases the attenuation of projectile and decreases the number of produced fragments. PARLEV(34) determines a phase space available for a break-up channel, and in this way it influences its probability. A decrease of PARLEV(33) increases the Coulomb barriers of the decay channels and suppresses them.

Results: The default values of 1.0 for PARLEV(39), (34) and (33) are changed to 0.8, 17 and 0.3, respectively. The decrease of PARLEV(39) improves the peak height of Bragg curves and the number of Carbon ions in the angular distributions. The new PARLEV(34) and (33) influence only the fragmentation and increase the number of H and He fragments and decrease the number of Li, Be and B. The mean underestimation of H fragments within the first 2° is reduced from 23% to less than 10%. The mean overestimation of Li of 16% is reduced down to 2%. The overestimation of Be by 200%, using the default values, is reduced down to 100%. The number of He and B fragments are not considerably improved by changing PARLEV(34) and (33).

The comparison with the experimental data shows that there might be some problems with the normalization of the data.

Conclusion: Changing PARLEV(39), (34) and (33) to 0.8, 17 and 0.3, respectively considerably improves the agreement with angular and depth distributions. The number of fragments are predicted more accurate and thus improves SHIELD-HIT simulations for radiobiological issues.


References

1.
Haettner E. Experimental study on carbon ion fragmentation in water using GSI therapy beams. Stockholm: Kungliga Tekniska Högskolan; 2006.
2.
Botvina AS, et al. MSDM – Multi Stage Dynamic Model; NSC/DOC(97)-1, NEA/P&T No 14, NEA OECD, Paris. 1997;14: 307.