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Initial beam size study for passive scatter proton therapy. II. Changes in delivered depth dose profiles.

Authors
  • Polf, Jerimy C
  • Harvey, Mark C
  • Smith, Alfred R
Type
Published Article
Journal
Medical Physics
Publisher
Wiley (John Wiley & Sons)
Publication Date
Nov 01, 2007
Volume
34
Issue
11
Pages
4219–4222
Identifiers
PMID: 18072486
Source
Medline
License
Unknown

Abstract

In passively scattered proton radiotherapy, a clinically useful treatment beam is produced by spreading a small proton "pencil beam" extracted from the accelerator to create both a uniform dose profile laterally and a uniform spread-out Bragg peak (SOBP) in depth. Lateral spreading and range modulation of the beam are accomplished using specially designed components within the treatment delivery nozzle. The purpose of this study was to determine how changes in the size of the initial proton pencil beam affect the delivery of dose with a passive scatter treatment nozzle. Monte Carlo calculations were used to study changes of the beam's in-air energy distribution at the exit of the nozzle and the central axis depth dose profiles in water resulting from changes in the incident beam size. Our results indicate that the width of the delivered SOBP decreases as the size of the initial beam increases.

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