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dc.contributor.authorThwaites, D I
dc.contributor.authorWilliams, J R
dc.contributor.authorAird, E G
dc.contributor.authorKlevenhagen, S C
dc.contributor.authorWilliams, Peter C
dc.date.accessioned2010-08-16T13:31:13Z
dc.date.available2010-08-16T13:31:13Z
dc.date.issued1992-02
dc.identifier.citationA dosimetric intercomparison of megavoltage photon beams in UK radiotherapy centres. 1992, 37 (2):445-61 Phys Med Biolen
dc.identifier.issn0031-9155
dc.identifier.pmid1553393
dc.identifier.doi10.1088/0031-9155/37/2/011
dc.identifier.urihttp://hdl.handle.net/10541/109640
dc.description.abstractA dosimetry intercomparison has been carried out for all 64 radiotherapy centres in the UK. Doses were measured with an ionization chamber in an epoxy resin water-substitute phantom of relatively simple geometry. Reference-point measurements were made for all MV photon beams. For 61 Co-60 beams, a mean ratio of measured-to-stated dose of 1.002 was observed with a standard deviation of 0.014, whilst for 100 MV x-ray beams, the corresponding figures were 1.003 and 0.015. 97% of beams lay within a +/- 3% deviation. One measurement was instrumental in discovering a large discrepancy. Doses were also investigated in two planned three-field distributions at one beam quality in each centre. One of these was in a homogeneous phantom, whilst the second included a lung-equivalent insert. Doses were measured at the central point and at four other points in the high dose volume. In both situations, the mean ratio of measured-to-calculated doses for all points was 1.008, with standard deviations of 0.027 and 0.035 for the uniform and non-uniform phantoms, respectively. Discrepancies over 5% were followed up. The work must be viewed in the context of other international intercomparisons and is an essential part of wider radiotherapy audit processes.
dc.language.isoenen
dc.subject.meshGreat Britain
dc.subject.meshHumans
dc.subject.meshModels, Structural
dc.subject.meshQuality Assurance, Health Care
dc.subject.meshRadiotherapy Dosage
dc.subject.meshRadiotherapy, High-Energy
dc.titleA dosimetric intercomparison of megavoltage photon beams in UK radiotherapy centres.en
dc.typeArticleen
dc.contributor.departmentDepartment of Medical Physics and Medical Engineering, University of Edinburg, UK.en
dc.identifier.journalPhysics in Medicine and Biologyen
html.description.abstractA dosimetry intercomparison has been carried out for all 64 radiotherapy centres in the UK. Doses were measured with an ionization chamber in an epoxy resin water-substitute phantom of relatively simple geometry. Reference-point measurements were made for all MV photon beams. For 61 Co-60 beams, a mean ratio of measured-to-stated dose of 1.002 was observed with a standard deviation of 0.014, whilst for 100 MV x-ray beams, the corresponding figures were 1.003 and 0.015. 97% of beams lay within a +/- 3% deviation. One measurement was instrumental in discovering a large discrepancy. Doses were also investigated in two planned three-field distributions at one beam quality in each centre. One of these was in a homogeneous phantom, whilst the second included a lung-equivalent insert. Doses were measured at the central point and at four other points in the high dose volume. In both situations, the mean ratio of measured-to-calculated doses for all points was 1.008, with standard deviations of 0.027 and 0.035 for the uniform and non-uniform phantoms, respectively. Discrepancies over 5% were followed up. The work must be viewed in the context of other international intercomparisons and is an essential part of wider radiotherapy audit processes.


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