Head scatter modelling for irregular field shaping and beam intensity modulation.

2.50
Hdl Handle:
http://hdl.handle.net/10541/94922
Title:
Head scatter modelling for irregular field shaping and beam intensity modulation.
Authors:
Hounsell, Alan R; Wilkinson, John M
Abstract:
Scattered radiation from within the treatment head can contribute significant dose to all parts of a radiotherapy treatment field. A multileaf collimator may be used to create an arbitrarily shaped field, and may also be used, under dynamic control, to modulate the beam intensity over the field. This method of intensity modulation is effectively a superposition of a large number of fields which have the same beam direction, but different shapes, and some of these shapes may have unusually small dimensions, particularly in the direction of the leaf movement. Two models for predicting the head scatter under these conditions have been investigated. These are a first-order Compton scatter approximation from the flattening filter, and an empirical fit to measured data using an exponential function. The first model only considers scatter from the flattening filter and has been applied to field sizes between 2 cm by 2 cm and 10 cm by 10 cm, where agreements are all within 1%. However it is not satisfactory at larger field sizes where small scatter contributions, from scattering sources other than the flattening filter, are integrated over large areas. The second model uses measured data between 4 cm by 4 cm and 30 cm by 30 cm to optimize the exponential function and is used to calculate the head scatter contribution for all field sizes. In this case good agreement is achieved over the full field size range, and hence this is a more generally applicable model. Results are presented for static irregularly shaped fields and intensity modulated beams created using a Philips multileaf collimator.
Affiliation:
North Western Medical Physics, Christie Hospital NHS Trust, Manchester, UK. phyarh@picr.cr.man.ac.uk
Citation:
Head scatter modelling for irregular field shaping and beam intensity modulation. 1997, 42 (9):1737-49 Phys Med Biol
Journal:
Physics in Medicine and Biology
Issue Date:
Sep-1997
URI:
http://hdl.handle.net/10541/94922
DOI:
10.1088/0031-9155/42/9/006
PubMed ID:
9308080
Type:
Article
Language:
en
ISSN:
0031-9155
Appears in Collections:
All Christie Publications ; All Paterson Institute for Cancer Research

Full metadata record

DC FieldValue Language
dc.contributor.authorHounsell, Alan Ren
dc.contributor.authorWilkinson, John Men
dc.date.accessioned2010-03-24T15:29:51Z-
dc.date.available2010-03-24T15:29:51Z-
dc.date.issued1997-09-
dc.identifier.citationHead scatter modelling for irregular field shaping and beam intensity modulation. 1997, 42 (9):1737-49 Phys Med Biolen
dc.identifier.issn0031-9155-
dc.identifier.pmid9308080-
dc.identifier.doi10.1088/0031-9155/42/9/006-
dc.identifier.urihttp://hdl.handle.net/10541/94922-
dc.description.abstractScattered radiation from within the treatment head can contribute significant dose to all parts of a radiotherapy treatment field. A multileaf collimator may be used to create an arbitrarily shaped field, and may also be used, under dynamic control, to modulate the beam intensity over the field. This method of intensity modulation is effectively a superposition of a large number of fields which have the same beam direction, but different shapes, and some of these shapes may have unusually small dimensions, particularly in the direction of the leaf movement. Two models for predicting the head scatter under these conditions have been investigated. These are a first-order Compton scatter approximation from the flattening filter, and an empirical fit to measured data using an exponential function. The first model only considers scatter from the flattening filter and has been applied to field sizes between 2 cm by 2 cm and 10 cm by 10 cm, where agreements are all within 1%. However it is not satisfactory at larger field sizes where small scatter contributions, from scattering sources other than the flattening filter, are integrated over large areas. The second model uses measured data between 4 cm by 4 cm and 30 cm by 30 cm to optimize the exponential function and is used to calculate the head scatter contribution for all field sizes. In this case good agreement is achieved over the full field size range, and hence this is a more generally applicable model. Results are presented for static irregularly shaped fields and intensity modulated beams created using a Philips multileaf collimator.en
dc.language.isoenen
dc.subject.meshBiophysical Phenomena-
dc.subject.meshBiophysics-
dc.subject.meshEquipment Design-
dc.subject.meshHumans-
dc.subject.meshModels, Theoretical-
dc.subject.meshParticle Accelerators-
dc.subject.meshRadiometry-
dc.subject.meshRadiotherapy, High-Energy-
dc.subject.meshScattering, Radiation-
dc.titleHead scatter modelling for irregular field shaping and beam intensity modulation.en
dc.typeArticleen
dc.contributor.departmentNorth Western Medical Physics, Christie Hospital NHS Trust, Manchester, UK. phyarh@picr.cr.man.ac.uken
dc.identifier.journalPhysics in Medicine and Biologyen
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