The effect of gantry angle on megavoltage photon beam attenuation by a carbon fiber couch insert.

2.50
Hdl Handle:
http://hdl.handle.net/10541/75845
Title:
The effect of gantry angle on megavoltage photon beam attenuation by a carbon fiber couch insert.
Authors:
McCormack, Stephen; Diffey, Jennifer; Morgan, Andrew
Abstract:
The use of rigid carbon fiber couch inserts in radiotherapy treatment couches is a well-established method of reducing patient set-up errors associated with couch sag. Several published studies have described such inserts as radiotranslucent with negligible attenuation of the radiation field. Most of these studies were conducted with the radiation field normally incident on the couch and there appears to be no evidence in the literature of the effect of the gantry angle on the extent of beam attenuation by the carbon fiber insert alone during external beam radiotherapy. In this study we examined the magnitude of this effect over a range of posterior oblique gantry angles using a cylindrical solid water phantom containing an ionization chamber placed isocentrically. It was found that a 6 MV photon beam, field size 10 x 5 cm, was attenuated significantly as the gantry angle approached the plane of the couch, from 2% at normal incidence and reaching 9% attenuation at angle of incidence 70 degrees. This could have serious implications regarding dose to the treatment volume for treatments requiring posterior oblique angles of incidence with a possible correction factor necessary in monitor unit calculations.
Affiliation:
Department of Medical Physics, Cookridge Hospital, Hospital Lane, Leeds LS16 6QB, England.
Citation:
The effect of gantry angle on megavoltage photon beam attenuation by a carbon fiber couch insert. 2005, 32 (2):483-7 Med Phys
Journal:
Medical Physics
Issue Date:
Feb-2005
URI:
http://hdl.handle.net/10541/75845
PubMed ID:
15789595
Type:
Article
Language:
en
ISSN:
0094-2405
Appears in Collections:
All Christie Publications

Full metadata record

DC FieldValue Language
dc.contributor.authorMcCormack, Stephen-
dc.contributor.authorDiffey, Jennifer-
dc.contributor.authorMorgan, Andrew-
dc.date.accessioned2009-07-29T12:33:29Z-
dc.date.available2009-07-29T12:33:29Z-
dc.date.issued2005-02-
dc.identifier.citationThe effect of gantry angle on megavoltage photon beam attenuation by a carbon fiber couch insert. 2005, 32 (2):483-7 Med Physen
dc.identifier.issn0094-2405-
dc.identifier.pmid15789595-
dc.identifier.urihttp://hdl.handle.net/10541/75845-
dc.description.abstractThe use of rigid carbon fiber couch inserts in radiotherapy treatment couches is a well-established method of reducing patient set-up errors associated with couch sag. Several published studies have described such inserts as radiotranslucent with negligible attenuation of the radiation field. Most of these studies were conducted with the radiation field normally incident on the couch and there appears to be no evidence in the literature of the effect of the gantry angle on the extent of beam attenuation by the carbon fiber insert alone during external beam radiotherapy. In this study we examined the magnitude of this effect over a range of posterior oblique gantry angles using a cylindrical solid water phantom containing an ionization chamber placed isocentrically. It was found that a 6 MV photon beam, field size 10 x 5 cm, was attenuated significantly as the gantry angle approached the plane of the couch, from 2% at normal incidence and reaching 9% attenuation at angle of incidence 70 degrees. This could have serious implications regarding dose to the treatment volume for treatments requiring posterior oblique angles of incidence with a possible correction factor necessary in monitor unit calculations.en
dc.language.isoenen
dc.subject.meshCarbon-
dc.subject.meshComputer Simulation-
dc.subject.meshHumans-
dc.subject.meshLinear Energy Transfer-
dc.subject.meshModels, Chemical-
dc.subject.meshPhotons-
dc.subject.meshRadiation Protection-
dc.subject.meshRadiometry-
dc.subject.meshRadiotherapy Dosage-
dc.subject.meshRadiotherapy, High-Energy-
dc.subject.meshSarcoma-
dc.subject.meshScattering, Radiation-
dc.titleThe effect of gantry angle on megavoltage photon beam attenuation by a carbon fiber couch insert.en
dc.typeArticleen
dc.contributor.departmentDepartment of Medical Physics, Cookridge Hospital, Hospital Lane, Leeds LS16 6QB, England.en
dc.identifier.journalMedical Physicsen

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