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Experimental determination of the effective point of measurement for cylindrical ionization chambers in 60Co gamma radiation.

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Title: Experimental determination of the effective point of measurement for cylindrical ionization chambers in 60Co gamma radiation.
Authors: Legrand, C.1 c.legrand@dkfz-heidelberg.de, Hartmann, G. H.1, Karger, C. P.1
Source: Physics in Medicine & Biology. Jun2012, Vol. 57 Issue 11, p3463-3475. 13p.
Subjects: Ionization chambers, Therapeutic use of gamma rays, Quantum perturbations, Radiation dosimetry, Distribution (Probability theory), Accuracy, Evaluation
Abstract: 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 perturbation factor. The dependence of these effects in water was examined as a function of the cavity radius using cylindrical chambers with different radii and a plane-parallel chamber, whose EPOM is well known. Depth-dose curves were measured in terms of absolute absorbed dose in water and evaluated according to the international protocol IAEA TRS-398 as well as the German protocol DIN 6800-2. As expected, evaluation of absorbed dose under reference conditions following both protocols agreed well within a standard uncertainty of 0.1%. However, values of absorbed dose at depths beyond the dose maximum showed deviations up to 0.3% and 0.5% for IAEA TRS-398 and DIN 6800-2, respectively. Values in the build-up and maximum region did not agree very well. Deviations of more than 1% were found for both protocols. It was concluded that the corrections recommended in both protocols are not fully appropriate. A procedure is suggested to measure the absorbed depth-dose distribution including the build-up region with an improved accuracy by means of cylindrical chambers. [ABSTRACT FROM AUTHOR]
© 2025 IOP Publishing Ltd. All rights, including for text and data mining, AI training, and similar technologies, are reserved (Copyright applies to all Abstracts.)
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An: 78125559
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  Data: Experimental determination of the effective point of measurement for cylindrical ionization chambers in <superscript>60</superscript>Co gamma radiation.
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  Data: <searchLink fieldCode="JN" term="%22Physics+in+Medicine+%26+Biology%22">Physics in Medicine & Biology</searchLink>. Jun2012, Vol. 57 Issue 11, p3463-3475. 13p.
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  Data: <searchLink fieldCode="DE" term="%22Ionization+chambers%22">Ionization chambers</searchLink><br /><searchLink fieldCode="DE" term="%22Therapeutic+use+of+gamma+rays%22">Therapeutic use of gamma rays</searchLink><br /><searchLink fieldCode="DE" term="%22Quantum+perturbations%22">Quantum perturbations</searchLink><br /><searchLink fieldCode="DE" term="%22Radiation+dosimetry%22">Radiation dosimetry</searchLink><br /><searchLink fieldCode="DE" term="%22Distribution+%28Probability+theory%29%22">Distribution (Probability theory)</searchLink><br /><searchLink fieldCode="DE" term="%22Accuracy%22">Accuracy</searchLink><br /><searchLink fieldCode="DE" term="%22Evaluation%22">Evaluation</searchLink>
– Name: Abstract
  Label: Abstract
  Group: Ab
  Data: 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 perturbation factor. The dependence of these effects in water was examined as a function of the cavity radius using cylindrical chambers with different radii and a plane-parallel chamber, whose EPOM is well known. Depth-dose curves were measured in terms of absolute absorbed dose in water and evaluated according to the international protocol IAEA TRS-398 as well as the German protocol DIN 6800-2. As expected, evaluation of absorbed dose under reference conditions following both protocols agreed well within a standard uncertainty of 0.1%. However, values of absorbed dose at depths beyond the dose maximum showed deviations up to 0.3% and 0.5% for IAEA TRS-398 and DIN 6800-2, respectively. Values in the build-up and maximum region did not agree very well. Deviations of more than 1% were found for both protocols. It was concluded that the corrections recommended in both protocols are not fully appropriate. A procedure is suggested to measure the absorbed depth-dose distribution including the build-up region with an improved accuracy by means of cylindrical chambers. [ABSTRACT FROM AUTHOR]
– Name: AbstractSuppliedCopyright
  Label:
  Group: Ab
  Data: <i>© 2025 IOP Publishing Ltd. All rights, including for text and data mining, AI training, and similar technologies, are reserved</i> (Copyright applies to all Abstracts.)
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      – Type: doi
        Value: 10.1088/0031-9155/57/11/3463
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      – Code: gre
        Text: Modern Greek
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        PageCount: 13
        StartPage: 3463
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      – SubjectFull: Ionization chambers
        Type: general
      – SubjectFull: Therapeutic use of gamma rays
        Type: general
      – SubjectFull: Quantum perturbations
        Type: general
      – SubjectFull: Radiation dosimetry
        Type: general
      – SubjectFull: Distribution (Probability theory)
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      – SubjectFull: Accuracy
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      – SubjectFull: Evaluation
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      – TitleFull: Experimental determination of the effective point of measurement for cylindrical ionization chambers in 60Co gamma radiation.
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              Text: Jun2012
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