The variation in output of symmetric, asymmetric and irregularly shaped wedged radiotherapy fields.

2.50
Hdl Handle:
http://hdl.handle.net/10541/95159
Title:
The variation in output of symmetric, asymmetric and irregularly shaped wedged radiotherapy fields.
Authors:
Hounsell, Alan R; Wilkinson, John M
Abstract:
A model for calculating the variation in output of symmetric, asymmetric and irregularly shaped wedged radiotherapy fields is presented. The variation in output from the treatment head when a wedge is used is calculated by dividing the output into a primary component and one due to scattered radiation. The scatter component is then further subdivided into contributions from elements which have a 1 cm x 1 cm cross-sectional area at the isocentre. The scatter from each element is determined as the contribution from the head scatter component modified by the presence of the wedge and a contribution due to additional scattered radiation from the wedge. The relative intensity of the scattered radiation from the wedge is modelled using a simple first scatter approximation. In this approximation the magnitude of the scatter is given by a t exp(-mu t) function where t is the thickness of the wedge for the selected element. The magnitude of the primary component and the relative intensity of scatter from each element are then obtained by an iterative fit to measured data. The technique has been applied to two different internally mounted wedge designs, for a standard treatment head, two asymmetric treatment heads and two similar multileaf collimators, over a range of energies between 4 and 20 MV. Calculations agree with measured values over a range of field sizes and shapes to within 1.5%.
Affiliation:
North Western Medical Physics, Christie Hospital, Manchester, UK.
Citation:
The variation in output of symmetric, asymmetric and irregularly shaped wedged radiotherapy fields. 1996, 41 (10):2155-72 Phys Med Biol
Journal:
Physics in Medicine and Biology
Issue Date:
Oct-1996
URI:
http://hdl.handle.net/10541/95159
DOI:
10.1088/0031-9155/41/10/021
PubMed ID:
8912387
Type:
Article
Language:
en
ISSN:
0031-9155
Appears in Collections:
All Christie Publications

Full metadata record

DC FieldValue Language
dc.contributor.authorHounsell, Alan Ren
dc.contributor.authorWilkinson, John Men
dc.date.accessioned2010-03-29T12:07:00Z-
dc.date.available2010-03-29T12:07:00Z-
dc.date.issued1996-10-
dc.identifier.citationThe variation in output of symmetric, asymmetric and irregularly shaped wedged radiotherapy fields. 1996, 41 (10):2155-72 Phys Med Biolen
dc.identifier.issn0031-9155-
dc.identifier.pmid8912387-
dc.identifier.doi10.1088/0031-9155/41/10/021-
dc.identifier.urihttp://hdl.handle.net/10541/95159-
dc.description.abstractA model for calculating the variation in output of symmetric, asymmetric and irregularly shaped wedged radiotherapy fields is presented. The variation in output from the treatment head when a wedge is used is calculated by dividing the output into a primary component and one due to scattered radiation. The scatter component is then further subdivided into contributions from elements which have a 1 cm x 1 cm cross-sectional area at the isocentre. The scatter from each element is determined as the contribution from the head scatter component modified by the presence of the wedge and a contribution due to additional scattered radiation from the wedge. The relative intensity of the scattered radiation from the wedge is modelled using a simple first scatter approximation. In this approximation the magnitude of the scatter is given by a t exp(-mu t) function where t is the thickness of the wedge for the selected element. The magnitude of the primary component and the relative intensity of scatter from each element are then obtained by an iterative fit to measured data. The technique has been applied to two different internally mounted wedge designs, for a standard treatment head, two asymmetric treatment heads and two similar multileaf collimators, over a range of energies between 4 and 20 MV. Calculations agree with measured values over a range of field sizes and shapes to within 1.5%.en
dc.language.isoenen
dc.subject.meshHumans-
dc.subject.meshModels, Theoretical-
dc.subject.meshParticle Accelerators-
dc.subject.meshPhantoms, Imaging-
dc.subject.meshRadiotherapy Planning, Computer-Assisted-
dc.subject.meshScattering, Radiation-
dc.titleThe variation in output of symmetric, asymmetric and irregularly shaped wedged radiotherapy fields.en
dc.typeArticleen
dc.contributor.departmentNorth Western Medical Physics, Christie Hospital, Manchester, UK.en
dc.identifier.journalPhysics in Medicine and Biologyen

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