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Comparison of measured and calculated radiotherapy doses in the chest region of an inhomogeneous humanoid phantom

Australasian Physics & Engineering Sciences in Medicine volume 27, Article number: 16 (2004) Cite this article

Abstract

Errors in dose calculation by treatment planning computers are known to arise when calculation algorithms do not account for electron disequilibrium near interfaces between tissues of different density. The accuracy of a treatment planning system (Plato, Nucletron International BV) was investigated for two treatments in the chest region: tangential 6MV photons to the chest wall and opposed AP-PA 18MV photon fields to the mediastinum. Thermo-luminescent dosimeters were used to measure dose at 40 sites in the chest of a humanoid phantom (Rando, Alderson Associates). Measurements were compared with point doses calculated using two different versions of the Plato external beam calculation software: RTS 1.8 and the newer RTS 2.2. Measured and calculated doses differed by 3% or more at more than one quarter of all sites. The greatest discrepancies occurred for points located in lung, which were generally over-estimated. The maximum discrepancies for the 6MV tangential breast irradiation were 8.5% for RTS 1.8 and 3.5% for RTS 2.2. For the 18MV opposed field irradiation, the maximum discrepancies were 11.4% and 8.1% respectively. RTS 2.2 was more accurate than RTS 1.8, with smaller mean and maximum discrepancies.

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Author notes

  1. L. McDermott

    Present address: Netherlands Cancer Institute, Amsterdam, The Netherlands

  2. A. Perkins

    Present address: Bendigo Radiotherapy Centre, Peter MacCallum Cancer Centre, PO Box 126, 3552, Bendigo, Vic, Australia

Affiliations

  1. William Buckland Radiotherapy Centre, The Alfred Hospital, Melbourne, Australia

    L. McDermott & A. Perkins

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  1. L. McDermott
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  2. A. Perkins
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Correspondence to A. Perkins.

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McDermott, L., Perkins, A. Comparison of measured and calculated radiotherapy doses in the chest region of an inhomogeneous humanoid phantom. Australas. Phys. Eng. Sci. Med. 27, 16 (2004). https://doi.org/10.1007/BF03178883

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  • DOI: https://doi.org/10.1007/BF03178883

Key words

  • lung corrections
  • electron disequilibrium
  • tangential breast irradiation
  • megavoltage chest irradiation