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dc.contributor.authorHounsell, Alan R
dc.contributor.authorWilkinson, John M
dc.date.accessioned2009-12-14T16:03:36Z
dc.date.available2009-12-14T16:03:36Z
dc.date.issued1999-01
dc.identifier.citationElectron contamination and build-up doses in conformal radiotherapy fields. 1999, 44 (1):43-55 Phys Med Biolen
dc.identifier.issn0031-9155
dc.identifier.pmid10071874
dc.identifier.doi10.1088/0031-9155/44/1/005
dc.identifier.urihttp://hdl.handle.net/10541/87913
dc.description.abstractThe dose in the build-up region depends upon the primary photon beam, backscattered radiation from the patient and contamination radiation from outside the patient. In this paper, a model based on measured data is proposed which allows the build-up dose for arbitrarily shaped treatment fields to be determined. The dose in the build-up region is assumed to comprise a primary photon component and a contamination component that is a function of the field size and shape. This contamination component, for modelling purposes, is subdivided into contributions that correspond to elements of 1 cm by 1 cm cross-sectional area at the plane of the isocentre. The magnitude of these components has been obtained by fitting measured data to an exponential function. The exponent was found to vary linearly with depth for energies between 4 MV and 20 MV. The coefficient decreased linearly with depth at 4, 6 and 8 MV, but exhibited a broad build-up region at 20 MV. The primary component, in the build-up region, could be approximated by a 100 - (100 - PSD) e(-mu d) function, where PSD is the primary surface dose. The values obtained during the fitting procedure were used to calculate dose in the build-up region for arbitrarily shaped fields. Good agreement was found in each case.
dc.language.isoenen
dc.subject.meshElectrons
dc.subject.meshHumans
dc.subject.meshPhantoms, Imaging
dc.subject.meshPhotons
dc.subject.meshRadiotherapy Dosage
dc.subject.meshRadiotherapy Planning, Computer-Assisted
dc.subject.meshRadiotherapy, Conformal
dc.subject.meshReproducibility of Results
dc.subject.meshScattering, Radiation
dc.titleElectron contamination and build-up doses in conformal radiotherapy fields.en
dc.typeArticleen
dc.contributor.departmentNorth Western Medical Physics, Christie Hospital NHS Trust, Manchester, UK. alan.hounsell@physics.cr.man.ac.uken
dc.identifier.journalPhysics in Medicine and Biologyen
html.description.abstractThe dose in the build-up region depends upon the primary photon beam, backscattered radiation from the patient and contamination radiation from outside the patient. In this paper, a model based on measured data is proposed which allows the build-up dose for arbitrarily shaped treatment fields to be determined. The dose in the build-up region is assumed to comprise a primary photon component and a contamination component that is a function of the field size and shape. This contamination component, for modelling purposes, is subdivided into contributions that correspond to elements of 1 cm by 1 cm cross-sectional area at the plane of the isocentre. The magnitude of these components has been obtained by fitting measured data to an exponential function. The exponent was found to vary linearly with depth for energies between 4 MV and 20 MV. The coefficient decreased linearly with depth at 4, 6 and 8 MV, but exhibited a broad build-up region at 20 MV. The primary component, in the build-up region, could be approximated by a 100 - (100 - PSD) e(-mu d) function, where PSD is the primary surface dose. The values obtained during the fitting procedure were used to calculate dose in the build-up region for arbitrarily shaped fields. Good agreement was found in each case.


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