Effective point of measurement of thimble ion chambers in megavoltage photon beams

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DOIResolve DOI: http://doi.org/10.1118/1.3266750
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TypeArticle
Journal titleMedical physics
Volume37
Issue1
Pages96107; # of pages: 12
SubjectBiomedical electrodes; Dosimetry; Ionisation chambers; Linear accelerators; Monte Carlo; Neurophysiology; Phantoms; Effective point of measurement
AbstractPurpose: Determine the effective point of measurement (EPOM) of 12 thimble ion chambers, including miniature chambers and three models widely used for clinical reference dosimetry. The EPOM is the point at which the measured dose would arise in the measurement medium in the absence of the probe: For cylindrical chambers, it is shifted upstream relative to the central axis of the chamber. Although current dosimetry protocols prescribe a blanket upstream EPOM shift of 0.6r, with r as the chamber cavity radius, it has been shown in recent years that the EPOM does, in fact, depend on every detail of the chamber design and on the beam characteristics. In the wake of this finding, the authors undertake a comprehensive study of the EPOM for a series of chambers in water.
Publication date
LanguageEnglish
AffiliationNational Research Council Canada (NRC-CNRC); NRC Institute for National Measurement Standards
Peer reviewedYes
NPARC number16378395
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Record identifier88834416-f4d9-4a7a-8a9f-7d414a21df57
Record created2010-11-15
Record modified2016-05-09
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