The influence of oblique incidence electron beams to beam specification parameters

Research output: Contribution to journalConference articlepeer-review

Abstract

The changes of beam specification parameters along the normal central axis of electron beams with increasing gantry angle had been measured. The electron beams were produced by Varian Clinac2100C with energies of 6, 9, 12, 16, and 20 MeV. This work was performed using Wellhőffer water phantom provided with two small cylindrical IC-15 chambers. It was found that the oblique incidence beams cause the dmax depth, Rp, R85 at normal central axis shifted to skin surface. For all energies, the changes of gantry angle from 0 to 20 shift the dmax depth in the range of 2.0 % up to 17.73 %, Rp in the range of 2.02 up to 10.78 %, and R85 in the range of 8.93 up to 9.37 %. The percentage ionization along the diagonal fanline was also measured. The results indicated that for lower energy electron beams (6 MeV, 9 MeV, and 12 MeV) the diagonal fanline was still located at the penumbra region (80 % -20% isodose line), whereas for higher energies (16 MeV and 20 MeV) these diagonal fanline were in radiation field area particularly for the gantry angle of 15° and 20°.

Original languageEnglish
Pages (from-to)1948-1951
Number of pages4
JournalIFMBE Proceedings
Volume14
Issue number1
Publication statusPublished - 1 Jan 2007
Event10th World Congress on Medical Physics and Biomedical Engineering, WC 2006 - Seoul, Korea, Republic of
Duration: 27 Aug 20061 Sep 2006

Keywords

  • Diagonal fanline
  • Electron beams
  • Oblique incidence
  • Penumbra

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