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

Secondary neutron doses measurement for the eye treatment proton therapy at the KNCC

Meeting Abstract

  • D. Kim - Proton therapy center, National Cancer Center, Ilsandong-gu, Korea, Republic of Korea
  • S. H. Ahn - Proton therapy center, National Cancer Center, Ilsandong-gu, Korea, Republic of Korea
  • S. Lee - Proton therapy center, National Cancer Center, Ilsandong-gu, Korea, Republic of Korea
  • S. Y. Park - Proton therapy center, National Cancer Center, Ilsandong-gu, Korea, Republic of Korea
  • J. Rha - Proton therapy center, National Cancer Center, Ilsandong-gu, Korea, Republic of Korea
  • U. Whang - Proton therapy center, National Cancer Center, Ilsandong-gu, Korea, Republic of Korea
  • M. Yoon - Proton therapy center, National Cancer Center, Ilsandong-gu, Korea, Republic of Korea

PTCOG 48. Meeting of the Particle Therapy Co-Operative Group. Heidelberg, 28.09.-03.10.2009. Düsseldorf: German Medical Science GMS Publishing House; 2009. Doc09ptcog111

DOI: 10.3205/09ptcog111, URN: urn:nbn:de:0183-09ptcog1119

Veröffentlicht: 24. September 2009

© 2009 Kim et al.
Dieser Artikel ist ein Open Access-Artikel und steht unter den Creative Commons Lizenzbedingungen (http://creativecommons.org/licenses/by-nc-nd/3.0/deed.de). Er darf vervielfältigt, verbreitet und öffentlich zugänglich gemacht werden, vorausgesetzt dass Autor und Quelle genannt werden.


Gliederung

Text

Purpose: Secondary neutrons are produced during the proton treatment by the nuclear interaction with the materials on the beam path including the patient's body. In this study, we measure the neutron dose from the eye treatment system of proton therapy and estimate the reducing of the secondary neutron dose by the SWX207HD5.

Methods and materials: To estimate the secondary neutron dose, a water phantom was irradiated with 123.36MeV proton beams using the eye treatment snout. A CR-39 etch detectors are used for the neutron dose measurement at the surface and middle of the water phantom. In addition, the secondary neutron doses are compared for the cases with and without borated nuetron absorber in the middle of the beam path.

Results: With the eye treatment beam delivery system, the maximum neutron dose equivalent to the proton absorbed dose is about 0.34±0.16 mSv/Gy at the 1.5 cm from the primary proton field edge in the perpendicular (90 degrees) directions on the surface of water phantom. A 3 cm thickness of neutron absorbing material which contains the 5.5% of borons and 5.7% of hydrogen in the PMMA, reduced a dose as 30% from original dose.

Conclusions: We conclude from measurements, the secondary neutron dose for the typical eye treatment beam is rangeing from 1.00 at 9.5 cm to 0.34 mSv/Gy at 1.5 cm displacement from a 4 cm diameter of the proton primary field edge on the surface. From this study, we found the absolute neutron dose from eye beam delivery system is relatively small comparing with normal large field cases and we also found that the neutron dose can be reduced as 30% by installing 3 cm thickness of a neutron absorbing material in the middle of beam line. The contributions to the integral dose by the secondary neutrons are very low and can be reduced more by installing a SWX207HD5 in the beam delivery system.