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

Multi-purpose nozzle for pencil beam scanning and wobbling

Meeting Abstract

  • T. Tachikawa - Quantum equipment division, Sumitomo Heavy Industries, Ltd., Soubiraki-cho, Niihama, Ehime, Japan
  • T. Ochi - Quantum equipment division, Sumitomo Heavy Industries, Ltd., Soubiraki-cho, Niihama, Ehime, Japan
  • T. Asaba - Quantum equipment division, Sumitomo Heavy Industries, Ltd., Soubiraki-cho, Niihama, Ehime, Japan
  • M. Yamada - Quantum equipment division, Sumitomo Heavy Industries, Ltd., Soubiraki-cho, Niihama, Ehime, Japan
  • T. Nishio - National Cancer Center Hospital East, Kashiwanoha, Kashiwa, Chiba, Japan
  • T. Ogino - National Cancer Center Hospital East, Kashiwanoha, Kashiwa, Chiba, 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. Doc09ptcog197

DOI: 10.3205/09ptcog197, URN: urn:nbn:de:0183-09ptcog1972

Published: September 24, 2009

© 2009 Tachikawa et al.
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Outline

Text

Purpose: Several types of pencil beam scanning system for proton therapy have been developed and applied to clinical treatment. However, most of them are designed for exclusive use of scanning method and, even if designed for dual purpose, it requires to change some devices in the nozzle. SHI has been developed a new multi-purpose nozzle in collaboration with NCCHE. Conventional wobbling irradiation as well as pencil beam scanning can be used without any change of devices.

Methods: The multi-purpose nozzle is equipped with all devises necessary for wobbling method including a fine resolution multi-leaf collimator. Range modulation is made by either ridge filters in the nozzle or by the energy selection system (ESS) just after the cyclotron. When the pencil beam scanning method is selected, the scatterer for wobbling, ridge filters, range shifter and the multi-leaf collimator are moved to their retracted positions. Quadrupole magnets located between the last bending magnet and two scanning magnets are also excited for focusing the beam at the isocenter.

In order to reduce the scattering effect by air in the nozzle, the vacuum is extended up to the exit of second scanning magnet. Because the size of vacuum pipe is small at this location, a thin foil can be used to as a vacuum window and a helium chamber is not needed. Beam size enhancement by scattering effect is sufficiently small, because the upstream half of beam path, which has a major contribution to the beam size at the isocenter, is in the vacuum.

The multi-leaf collimator has leaves of 3mm and 5mm thickness and its field size is more than 200 mm x 200 mm at the isocenter when it is located at the minimum distance from the isocenter. It can be moved in the beam axis direction and also can be rotated 180 deg around the beam axis.

Results: The multi-purpose nozzle has been installed in the gantry No.1 at NCCHE in early 2008 for its performance tests in collaboration with NCCHE. Pencil beam size was measured at several incident energies and gave good agreement with calculations. The performance test was done and the field size of 200 mm x 200 mm was demonstrated for both scanning and wobbling methods.

Conclusions: The multi-purpose nozzle for pencil beam scanning and wobbling methods has been developed and the required specifications are confirmed.