| Experimental determination of the effective point of measurement and the displacement correction factor for cylindrical ionization chambers in a 6 MV photon beam. | |
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MedLine Citation:
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PMID: 23038082 Owner: NLM Status: Publisher |
Abstract/OtherAbstract:
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The displacement effect of cylindrical ionization chambers is taken into account either by an effective point of measurement (EPOM) or, alternatively, by using a displacement correction factor. The dependence of these effects on water was examined as a function of the cavity radius for (60)Co gamma radiation in a previous paper. This paper describes results for high-energy photon beams using the same measurement technique. Additionally, the displacement correction factor was directly measured. Absorbed doses measured under reference conditions following the international protocol IAEA TRS-398 and the German protocol DIN 6800-2 agreed well between the chambers with different cavity radii within a standard uncertainty of 0.2%. However, there was a constant difference of 0.2% between both protocols. Similar to our observations made in (60)Co, absorbed doses measured with the different chambers at depths beyond the maximum showed deviations of up to 0.6% and 0.5% for IAEA TRS-398 and DIN 6800-2, respectively, and deviations of more than 1% were found for both protocols in the build-up and maximum region. We therefore propose modified formulas for the determination of the EPOM and the displacement correction factor. |
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Authors:
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C Legrand; G H Hartmann; C P Karger |
Publication Detail:
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Type: JOURNAL ARTICLE Date: 2012-10-05 |
Journal Detail:
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Title: Physics in medicine and biology Volume: 57 ISSN: 1361-6560 ISO Abbreviation: Phys Med Biol Publication Date: 2012 Oct |
Date Detail:
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Created Date: 2012-10-5 Completed Date: - Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 0401220 Medline TA: Phys Med Biol Country: - |
Other Details:
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Languages: ENG Pagination: 6869-6880 Citation Subset: - |
Affiliation:
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Department of Medical Physics in Radiation Oncology, German Cancer Research Center, Im Neuenheimer Feld 280, 69120 Heidelberg, Germany. |
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From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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