Monitor chamber backscatter for intensity modulated radiation therapy using multileaf collimators.

2.50
Hdl Handle:
http://hdl.handle.net/10541/92015
Title:
Monitor chamber backscatter for intensity modulated radiation therapy using multileaf collimators.
Authors:
Hounsell, Alan R
Abstract:
Backscattered radiation into the machine monitor chamber can affect the machine output variation, with changes in field size and shape. For intensity modulated radiation therapy (IMRT) where many field, which may have small dimensions, are summed to give an intensity modulated field, the magnitude of backscatter will be different due to both the backscattering surface area changing, and the delivered monitor units being larger than for the equivalent static field. The effect of backscatter variation with field size for a Philips SL15 accelerator has been investigated at 8 MV for static and IMRT fields both in the standard clinical operating condition where an anti-backscatter plate is fitted, and also for a case where the anti-backscatter plate has been removed. The results show that in the absence of the anti-backscatter plate the variation in output between a 4 cm by 4 cm field and a 40 cm by 40 cm field size due to backscattered radiation was 5% for static fields. The anti-backscatter plate reduced this variation to less than 1%. When the accelerator operated in IMRT mode, with the backscatter plate in place, changes in the output due to additional backscattered radiation were less than 0.3%. With the backscatter plate removed, the outputs were lower, indicating the presence of additional backscattered radiation. It can be concluded that for the Philips MLC and SL accelerator with its anti-backscatter plate, the effects of backscattered radiation can be ignored for both static and IMRT fields.
Affiliation:
North Western Medical Physics, Christie Hospital NHS Trust, Manchester, UK. prsarh@dalpha2.cr.man.ac.uk
Citation:
Monitor chamber backscatter for intensity modulated radiation therapy using multileaf collimators. 1998, 43 (2):445-54 Phys Med Biol
Journal:
Physics in Medicine and Biology
Issue Date:
Feb-1998
URI:
http://hdl.handle.net/10541/92015
DOI:
10.1088/0031-9155/43/2/017
PubMed ID:
9547177
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.date.accessioned2010-02-12T15:09:23Z-
dc.date.available2010-02-12T15:09:23Z-
dc.date.issued1998-02-
dc.identifier.citationMonitor chamber backscatter for intensity modulated radiation therapy using multileaf collimators. 1998, 43 (2):445-54 Phys Med Biolen
dc.identifier.issn0031-9155-
dc.identifier.pmid9547177-
dc.identifier.doi10.1088/0031-9155/43/2/017-
dc.identifier.urihttp://hdl.handle.net/10541/92015-
dc.description.abstractBackscattered radiation into the machine monitor chamber can affect the machine output variation, with changes in field size and shape. For intensity modulated radiation therapy (IMRT) where many field, which may have small dimensions, are summed to give an intensity modulated field, the magnitude of backscatter will be different due to both the backscattering surface area changing, and the delivered monitor units being larger than for the equivalent static field. The effect of backscatter variation with field size for a Philips SL15 accelerator has been investigated at 8 MV for static and IMRT fields both in the standard clinical operating condition where an anti-backscatter plate is fitted, and also for a case where the anti-backscatter plate has been removed. The results show that in the absence of the anti-backscatter plate the variation in output between a 4 cm by 4 cm field and a 40 cm by 40 cm field size due to backscattered radiation was 5% for static fields. The anti-backscatter plate reduced this variation to less than 1%. When the accelerator operated in IMRT mode, with the backscatter plate in place, changes in the output due to additional backscattered radiation were less than 0.3%. With the backscatter plate removed, the outputs were lower, indicating the presence of additional backscattered radiation. It can be concluded that for the Philips MLC and SL accelerator with its anti-backscatter plate, the effects of backscattered radiation can be ignored for both static and IMRT fields.en
dc.language.isoenen
dc.subject.meshAlloys-
dc.subject.meshCalibration-
dc.subject.meshCopper-
dc.subject.meshEquipment Design-
dc.subject.meshParticle Accelerators-
dc.subject.meshPhantoms, Imaging-
dc.subject.meshRadiation Monitoring-
dc.subject.meshRadiotherapy-
dc.subject.meshScattering, Radiation-
dc.subject.meshZinc-
dc.titleMonitor chamber backscatter for intensity modulated radiation therapy using multileaf collimators.en
dc.typeArticleen
dc.contributor.departmentNorth Western Medical Physics, Christie Hospital NHS Trust, Manchester, UK. prsarh@dalpha2.cr.man.ac.uken
dc.identifier.journalPhysics in Medicine and Biologyen
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